Ethylene oxide, also called
oxirane, is the
organic compoundAn organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
. It is a cyclic ether. This means that it is composed of two alkyl groups attached to an oxygen atom in a cyclic shape (circular). This colorless flammable gas with a faintly sweet odor is the simplest
epoxideAn epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in...
, a three-membered ring consisting of two carbon and one oxygen atom. Because of its special molecular structure, ethylene oxide easily participates in the
addition reactionAn addition reaction, in organic chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one....
, opening its cycle, and thus easily polymerizes. Ethylene oxide is
isomerIn chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
ic with
acetaldehydeAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
.
Although it is a vital raw material with diverse applications, including the manufacture of products like polysorbate-20 and
polyethylene glycolPolyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...
that are often more effective and less toxic than alternative materials, ethylene oxide itself is a very hazardous substance: at room temperature it is a flammable, carcinogenic, mutagenic, irritating, and anaesthetic gas with a misleadingly pleasant aroma.
The chemical reactivity that is responsible for many of ethylene oxide's hazards has also made it a key industrial chemical that supports the living standards of advanced societies. Although too dangerous for direct household use and generally unfamiliar to consumers, ethylene oxide is used industrially for making many consumer products as well as non-consumer chemicals and intermediates. Ethylene oxide is important or critical to the production of detergents, thickeners, solvents, plastics, and various organic chemicals such as
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
, ethanolamines, simple and complex glycols, polyglycol ethers and other compounds. As a poison gas that leaves no residue on items it contacts, pure ethylene oxide is a disinfectant that is widely used in hospitals and the medical equipment industry to replace steam in the sterilization of heat-sensitive tools and equipment, such as disposable plastic syringes.
Ethylene oxide is industrially produced by direct oxidation of
ethyleneEthylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
in the presence of
silverSilver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
catalyst. It is extremely flammable and explosive and is used as a main component of
thermobaric weaponA thermobaric weapon, which includes the type known as a "fuel-air bomb", is an explosive weapon that produces a blast wave of a significantly longer duration than those produced by condensed explosives. This is useful in military applications where its longer duration increases the numbers of...
s; therefore, it is commonly handled and shipped as a refrigerated liquid.
History
Ethylene oxide was first reported in 1859 by the
FrenchThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
chemist
Charles-Adolphe WurtzAdolphe Wurtz was an Alsatian French chemist. He is best remembered for his decades-long advocacy for the atomic theory and for ideas about the structures of chemical compounds, against the skeptical opinions of chemists such as Marcellin Berthelot and Etienne Henri Sainte-Claire Deville...
, who prepared it by treating
2-chloroethanol2-Chloroethanol is an organochlorine compound with the formula HOCH2CH2Cl. This colorless liquid has a pleasant ether-like odor. It is miscible with water...
with
potassium hydroxidePotassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
:
- Cl–CH2CH2–OH + KOH → (CH2CH2)O + KCl + H2O
Wurtz measured the
boiling pointThe boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
of ethylene oxide as 13.5 °C, slightly higher than the present value, and discovered the ability of ethylene oxide to react with acids and salts of metals. Wurtz mistakenly assumed that ethylene oxide has the properties of an organic base. This misconception persisted until 1896 when
Georg BredigGeorg Bredig was a German physicochemist .He taught at the Karlsruhe University .- Works :* Handbuch der Angewandten Physikalischen Chemie...
found that ethylene oxide is not an
electrolyteIn chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
. Its distinct difference with
etherEthers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
s, in particular, its propensity to join the addition reactions typical of unsaturated compounds, had long been a matter of debate. Only in 1893, the heterocyclic triangular structure of ethylene oxide had been proposed.
The first synthesis method had long remained the only, despite numerous attempts of scientists, including Wurtz himself, to produce ethylene oxide directly from
ethyleneEthylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
. Only in 1931, French chemist Theodore Lefort developed a method of direct oxidation of ethylene in the presence of
silverSilver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
catalyst. Since 1940, almost all industrial production of ethylene oxide has used this process. Sterilization by ethylene oxide for the preservation of
spiceA spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. It may be used to flavour a dish or to hide other flavours...
s was patented in 1938 by the
AmericanThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
chemist
Lloyd HallLloyd Augustus Hall was an African American chemist who contributed to the science of food preservation. By the end of his career, Hall had amassed 59 United States patents, and a number of his inventions were also patented in other countries.-Biography:Hall was born in Elgin, Illinois on June...
. Ethylene oxide achieved industrial importance during
World War IWorld War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
as a precursor to both the coolant
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
and the chemical weapon
mustard gasThe sulfur mustards, or sulphur mustards, commonly known as mustard gas, are a class of related cytotoxic, vesicant chemical warfare agents with the ability to form large blisters on exposed skin. Pure sulfur mustards are colorless, viscous liquids at room temperature...
.
Molecular structure and properties
The epoxy cycle of ethylene oxide is an almost regular triangle with bond angles of about 60° and a significant angular stress corresponding to the energy of 105 kJ/mol. For comparison, in
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s the C–O–H angle is about 110°; in
etherEthers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
s, the C–O–C angle is 120°. The
moment of inertiaIn classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...
about the principal axes are
IA = 32.921×10
−40 g·cm²,
IB = 37.926×10
−40 g·cm² and
IC = 59.510×10
−40 g·cm². The
dipole momentThe bond dipole moment uses the idea of electric dipole moment to measure the polarity of a chemical bond within a molecule. The bond dipole μ is given by:\mu = \delta \, d....
at a temperature in the range 17–176 °C is 6.26×10
−30 C·m.
The relative instability of the carbon-oxygen bonds in the molecule is revealed by the comparison in the table of the energy required to break two C–O bonds in the ethylene oxide or one C–O bond in
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
and
dimethyl etherDimethyl ether , also known as methoxymethane, is the organic compound with the formula . The simplest ether, it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant. When combusted, DME produces minimal soot and CO, though HC and NOx formation is...
:
! Reaction
! ΔH°
298, kJ/mol
! Method>
| (C2H4)O → C2H4 + O (cleavage of two bonds) |
354.38 |
Calculated, from atomic enthalpies |
C2H5OHEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
→ C2H5 + OH (breaking one bond) |
405.85 |
Electron impact |
CH3OCH3Dimethyl ether , also known as methoxymethane, is the organic compound with the formula . The simplest ether, it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant. When combusted, DME produces minimal soot and CO, though HC and NOx formation is...
→ CH3O + CH3 (breaking one bond) |
334.72 |
This instability determines the chemical activity of ethylene oxide and explains the ease of opening its cycle in
addition reactionAn addition reaction, in organic chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one....
s (see Chemical properties).
Physical properties
Ethylene oxide is a colorless gas at 25 °C and is a mobile liquid at 0 °C – viscosity of liquid ethylene oxide at 0 °C is about 5.5 times lower than that of water. The gas has a characteristic sweet odor of ether, noticeable when its concentration in air exceeds 500 ppm. Ethylene oxide is readily soluble in water,
ethanolEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
,
diethyl etherDiethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
and many organic solvents.
Main thermodynamical constants are:
- Standard molar heat capacity
Heat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
, Cp° = 48.19 J/(mol·K);
- Standard enthalpy
Enthalpy is a measure of the total energy of a thermodynamic system. It includes the internal energy, which is the energy required to create a system, and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure.Enthalpy is a...
of formation, ΔH°298 = –51.037 kJ/mol;
- Standard entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...
, S°298 = 243.4 J/(mol·K);
- Gibbs free energy
In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a thermodynamic system at a constant temperature and pressure...
, ΔG°298 = –11.68 kJ/mol;
- Heat of combustion
The heat of combustion is the energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions. The chemical reaction is typically a hydrocarbon reacting with oxygen to form carbon dioxide, water and heat...
, ΔHc° = –1306 kJ/mol.
The
surface tensionSurface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
of liquid ethylene oxide, at the interface with its own steam, is 35.8 mJ/m
2 at –50.1 °C and 27.6 mJ/m
2 at –0.1 °C.
The boiling point increases with the vapor pressure as follows:
57.7 (2 atm), 83.6 (5 atm) and 114.0 (10 atm).
ViscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
decreases with temperature with the values of 0.577 kPa·s at –49.8 °C, 0.488 kPa·s at –38.2 °C, 0.394 kPa·s at –21.0 °C and 0.320 kPa·s at 0 °C.
Between –91 °C and 10.5 °C, vapor pressure
p (in mmHg) varies with temperature (T in °C) as lg
p = 6.251 – 1115.1/(244.14 + T).
Properties of liquid ethylene oxide
! Temperature, °C
! Steam pressure, kPa
! Enthalpy of the liquid,
J/g
! Enthalpy of vaporization,
J/g
! Density, kg/L
! Heat capacityHeat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
, J/(kg·K)
! Thermal conductivityIn physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
, W/(m·K)
| –40 °C |
8.35 |
0 |
628.6 |
0.9488 |
1878 |
0.20 |
| –20 °C |
25.73 |
38.8 |
605.4 |
0.9232 |
1912 |
0.18 |
| 0 °C |
65.82 |
77.3 |
581.7 |
0.8969 |
1954 |
0.16 |
| 20 °C |
145.8 |
115.3 |
557.3 |
0.8697 |
2008 |
0.15 |
| 40 °C |
288.4 |
153.2 |
532.1 |
0.8413 |
2092 |
0.14 |
| 60 °C |
521.2 |
191.8 |
505.7 |
0.8108 |
2247 |
0.14 |
| 80 °C |
875.4 |
232.6 |
477.4 |
0.7794 |
2426 |
0.14 |
| 100 °C |
1385.4 |
277.8 |
445.5 |
0.7443 |
2782 |
0.13 |
| 120 °C |
2088 |
330.4 |
407.5 |
0.7052 |
3293 |
N/A* |
| 140 °C |
3020 |
393.5 |
359.4 |
0.6609 |
4225 |
N/A |
| 160 °C |
4224 |
469.2 |
297.1 |
0.608 |
N/A |
N/A |
| 180 °C |
5741 |
551.2 |
222.5 |
0.533 |
N/A |
N/A |
| 195.8 °C |
7191 |
N/A |
N/A |
N/A |
N/A |
*N/A – data not available.
Properties of ethylene oxide vapor
! Temperature, K
! Entropy, J/(mol·K)
! Heat of formation, kJ/mol
! Free energy of formation, kJ/mol
! Viscosity Pa·s
! Thermal conductivity, W/(m·K)
! Heat capacity, J/(mol·K)
| 298 |
242.4 |
–52.63 |
–13.10 |
N/A |
N/A |
48.28 |
| 300 |
242.8 |
–52.72 |
–12.84 |
9.0 |
0.012 |
48.53 |
| 400 |
258.7 |
–56.53 |
1.05 |
13.5 |
0.025 |
61.71 |
| 500 |
274.0 |
–59.62 |
15.82 |
15.4 |
0.038 |
75.44 |
| 600 |
288.8 |
–62.13 |
31.13 |
18.2 |
0.056 |
86.27 |
| 700 |
302.8 |
–64.10 |
46.86 |
20.9 |
0.075 |
95.31 |
| 800 |
316.0 |
–65.61 |
62.80 |
N/A |
0.090 |
102.9 |
*N/A – data not available.
Chemical properties
Ethylene oxide readily reacts with various compounds, breaking a C–O bond and opening the cycle. Its typical reactions are with nucleophiles which proceed via the
SN2In organic and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which an electron nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms called the leaving group; the positive or partially positive...
mechanism both in acidic (weak nucleophiles: water, alcohols) and alkaline media (strong nucleophiles: OH
–, RO
–, NH
3, RNH
2, RR'NH, etc.). The general reaction scheme is
-
and more specific reactions are described below.
Addition of water and alcohols
Aqueous solutions of ethylene oxide are rather stable and can exist for a long time without any noticeable chemical reaction, but adding a small amount of acid, such as strongly diluted
sulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
, immediately leads to the formation of
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
, even at room temperature:
- (CH2CH2)O + H2O → HO–CH2CH2–OH
The reaction also occurs in the gas phase, in the presence of a
phosphoric acidPhosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
salt as a catalyst.
The reaction is usually carried out at about 60 °C with a large excess of water, in order to prevent the reaction of the formed ethylene glycol with ethylene oxide that would form di- and
triethylene glycolTriethylene glycol, TEG, or triglycol is a colorless odorless viscous liquid with molecular formula HOCH2CH2OCH2CH2OCH2CH2OH. It is used as a plasticizer for vinyl. It is also used in air sanitizer products, such as "Oust" or "Clean and Pure." When aerosolized it acts as a disinfectant...
:
- 2 (CH2CH2)O + H2O → HO–CH2CH2–O–CH2CH2–OH
- 3 (CH2CH2)O + H2O → HO–CH2CH2–O–CH2CH2–O–CH2CH2–OH
The use of alkaline catalysts may lead to the formation of
polyethylene glycolPolyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...
:
- n (CH2CH2)O + H2O → HO–(–CH2CH2–O–)n–H
Reactions with
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s proceed similarly yielding ethylene glycol ethers:
- (CH2CH2)O + C2H5OH → HO–CH2CH2–OC2H5
- 2 (CH2CH2)O + C2H5OH → HO–CH2CH2–O–CH2CH2–OC2H5
Reactions with lower alcohols occur less actively than with water and require more severe conditions, such as heating to 160 °C and pressurizing to 3 MPa and adding an acid or alkali catalyst.
Reactions of ethylene oxide with fatty alcohols proceed in the presence of
sodiumSodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
metal,
sodium hydroxide or
boron trifluorideBoron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...
and are used for the synthesis of surfactants.
Addition of carboxylic acids and their derivatives
Reactions of ethylene oxide with
carboxylic acidCarboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
s in the presence of a catalyst results in incomplete and with anhydrides in complete glycol esters:
- (CH2CH2)O + CH3COOH → HO–CH2CH2–OCOCH3
- (CH2CH2)O + (CH3CO)2O → CH3COO–CH2CH2–OCOCH3
The addition of acid
amideIn chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...
s proceeds similarly:
- (CH2CH2)O + CH3CONH2 → HO–CH2CH2–NHCOCH3
Addition of ethylene oxide to higher carboxylic acids is carried out at elevated temperatures (typically 140–180 °C) and pressure (0.3–0.5 MPa) in an inert atmosphere, in presence of an alkaline catalyst (concentration 0.01–2%), such as hydroxide or carbonate of sodium or potassium. The carboxylate ion acts as
nucleophileA nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...
in the reaction:
- RCOOH + OH– → RCOO– + H2O
- (CH2CH2)O + RCOO– → RCOOCH2CH2O–
- RCOOCH2CH2O– + RCOOH → RCOOCH2CH2OH + RCOO–
Adding ammonia and amines
Ethylene oxide reacts with
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
forming a mixture of mono-, di- and triethanolamine. The reaction is stimulated by adding a small amount of water.
- (CH2CH2)O + NH3 → HO–CH2CH2–NH2
- 2 (CH2CH2)O + NH3 → (HO–CH2CH2)2NH
- 3 (CH2CH2)O + NH3 → (HO–CH2CH2)3N
Similarly proceed the reactions with primary and secondary amines:
- (CH2CH2)O + RNH2 → HO–CH2CH2–NHR
Dialkylamino ethanols can further react with ethylene oxide, forming amino polyethylene glycols:
- n (CH2CH2)O + R2NCH2CH2OH → R2NCH2CH2O–(–CH2CH2O–)n–H
Trimethylamine reacts with ethylene oxide in the presence of water, forming
cholineCholine is a water-soluble essential nutrient. It is usually grouped within the B-complex vitamins. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation....
:
- (CH2CH2)O + (CH3)3N + H2O → [HOCH2CH2N (CH3)3]+OH–
Aromatic primary and secondary amines also react with ethylene oxide, forming the corresponding arylamino alcohols.
Halide addition
Ethylene oxide readily reacts with aqueous solutions of
hydrochloricHydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
,
hydrobromicHydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at 124.3 °C and contains 47.6% HBr by weight, which is 8.89 mol/L. Hydrobromic acid has a pKa of −9, making it a...
and hydroiodic acids to form
halohydrinA halohydrin or a haloalcohol is a type of organic compound or functional group in which one carbon atom has a halogen substituent, and an adjacent carbon atom has a hydroxyl substituent. They are derived from alcohols are therefore characterized by the presence of both the hydroxyl functional...
s. The reaction occurs easier with the last two acids:
- (CH2CH2)O + HCl → HO–CH2CH2–Cl
The reaction with these acids competes with the acid-catalyzed hydration of ethylene oxide; therefore, there is always a by-product of ethylene glycol with an admixture of diethylene glycol. For a cleaner product, the reaction is conducted in the gas phase or in an organic solvent.
Ethylene fluorohydrin is obtained differently, by boiling
hydrogen fluorideHydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
with a 5–6% solution of ethylene oxide in
diethyl etherDiethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
. The ether normally has a water content of 1.5–2%; in absence of water, ethylene oxide polymerizes.
Halohydrins can also be obtained by passing ethylene oxide through aqueous solutions of metal halides:
- 2 (CH2CH2)O + CuCl2 + 2 H2O → 2 HO–CH2CH2–Cl + Cu(OH)2↓
Metalorganic addition
Interaction of ethylene oxide with organomagnesium compounds, which are
Grignard reagentsThe Grignard reaction is an organometallic chemical reaction in which alkyl- or aryl-magnesium halides add to a carbonyl group in an aldehyde or ketone. This reaction is an important tool for the formation of carbon–carbon bonds...
, can be regarded as
nucleophilic substitutionIn organic and inorganic chemistry, nucleophilic substitution is a fundamental class of reactions in which an electron nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms called the leaving group; the positive or partially positive...
influenced by
carbanionA carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons. The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid.where B...
organometallic compounds. The final product of the reaction is a primary alcohol:
-
Similar mechanism is valid for other organometallic compounds, such as alkyl lithium:
-
Addition of hydrogen cyanide
Ethylene oxide easily reacts with the
hydrogen cyanide forming ethylene cyanohydrin:
- (CH2CH2)O + HCN → HO–CH2CH2–CN
A slightly chilled (10–20 °C) aqueous solution of
calcium cyanideCalcium cyanide is an inorganic compound with the formula Ca2. It is the calcium salt of hydrogen cyanide. At normal conditions, it appears as colorless crystals or white powder with characteristic odor of bitter almonds . Like other similar cyanides it is very toxic...
can be used instead of HCN:
- 2 (CH2CH2)O + Ca(CN)2 + 2 H2O → 2 HO–CH2CH2–CN + Ca(OH)2
Ethylene cyanohydrin easily loses water, producing
acrylonitrileAcrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...
:
- HO–CH2CH2–CN → CH2=CH–CN + H2O
Addition of hydrogen sulfide and mercaptans
When reacting with the
hydrogen sulfideHydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
, ethylene oxide forms 2-mercaptoethanol and thiodiglycol, and with alkylmercaptans it produces 2-alkyl mercaptoetanol:
- (CH2CH2)O + H2S → HO–CH2CH2–HS
- 2 (CH2CH2)O + H2S → (HO–CH2CH2)2S
- (CH2CH2)O + RHS → HO–CH2CH2–SR
The excess of ethylene oxide with an aqueous solution of hydrogen sulfide leads to the tris-(hydroxyethyl) sulfonyl hydroxide:
- 3 (CH2CH2)O + H2S → [(HO–CH2CH2)3S+]OH–
Addition of nitrous and nitric acids
Reaction of ethylene oxide with aqueous solutions of barium nitrite, calcium nitrite, magnesium nitrite, zinc nitrite or
sodium nitriteSodium nitrite is the inorganic compound with the chemical formula NaNO2. It is a white to slight yellowish crystalline powder that is very soluble in water and is hygroscopic...
leads to the formation of 2-nitroethanole:
- 2 (CH2CH2)O + Ca(NO2)2 + 2 H2O → 2 HO–CH2CH2–NO2 + Ca(OH)2
With
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, ethylene oxide forms mono- and
dinitroglycols:
-
Reaction with compounds containing active methylene groups
In the presence of alcoholates, reactions of ethylene oxide with compounds containing active methylene group leads to the formation of
butyrolactonegamma-Butyrolactone is a hygroscopic colorless oily liquid with a weak characteristic odor and is soluble in water. GBL is a common solvent and reagent in chemistry and is used as an aroma compound, as a stain remover, as a superglue remover, as a paint stripper, and as a solvent in some wet...
s:
-
Additions with aromatic compounds
Ethylene oxide enters into the
Friedel-Crafts reactionThe Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877. There are two main types of Friedel–Crafts reactions: alkylation reactions and acylation reactions. This reaction type is a form of electrophilic aromatic substitution...
with benzene to form
phenethyl alcoholPhenethyl alcohol, or 2-phenylethanol, is the organic compound with the formula C6H5CH2CH2OH. This colourless liquid occurs widely in nature, being found in a variety of essential oils, including rose, carnation, hyacinth, Aleppo pine, orange blossom, ylang-ylang, geranium, neroli, and champaca...
:
-
Styrene can be obtained in one stage if this reaction is conducted at elevated temperatures (315–440 °C) and pressures (0.35–0.7 MPa), in presence of an aluminosilicate catalyst.
Synthesis of crown ethers
A series of polynomial
heterocyclic compoundA heterocyclic compound is a cyclic compound which has atoms of at least two different elements as members of its ring. The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element....
s, known as
crown etherCrown ethers are cyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., -CH2CH2O-. Important members of this series are the tetramer , the pentamer , and the hexamer...
s, can be synthesized with ethylene oxide. One method is the cationic cyclopolymerization of ethylene oxide, limiting the size of the formed cycle:
- n (CH2CH2)O → (–CH2CH2–O–)n
To suppress the formation of other linear polymers the reaction is carried out in a highly dilute solution.
Reaction of ethylene oxide with
sulfur dioxideSulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
in the presence of caesium salts leads to the formation of an 11-membered heterocyclic compound which has the complexing properties of crown ethers:
-
Isomerization
When ethylene oxide is heated to about 400 °C, or to 150–300 °C in the presence of a catalyst (
Al2O3Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...
,
H3PO4Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
, etc.), it isomerizes into
acetaldehydeAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
:
-
The radical mechanism was proposed by Sidney W. Benson to explain this reaction in the gas phase; it comprises the following stages:
1) (CH
2CH
2)O ↔ •CH
2CH
2O• → CH
3CHO*
2) CH
3CHO* → CH
3• + CHO•
3) CH
3CHO* + M → CH
3CHO + M*
In reaction 3),
M refers to the wall of the reaction vessel or to a heterogeneous catalyst.
The moiety CH
3CHO* represents a short-lived (lifetime of 10
–8.5 seconds), activated molecule of acetaldehyde. Its excess energy is about 355.6 kJ/mol, which exceeds by 29.3 kJ/mol the
binding energyBinding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together—often this means that energy is released upon the creation of a bound state...
of the C-C bond in acetaldehyde.
In absence of a catalyst, the thermal isomerization of ethylene oxide is never selective and apart from acetaldehyde yields significant amount of by-products (see section Thermal decomposition).
Reduction reaction
Ethylene oxide can be hydrogenated into ethanol in the presence of a catalyst, such as
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
,
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
,
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...
,
boraneIn chemistry, a borane is a chemical compound of boron and hydrogen. The boranes comprise a large group of compounds with the generic formulae of BxHy. These compounds do not occur in nature. Many of the boranes readily oxidise on contact with air, some violently. The parent member BH3 is called...
s,
lithium aluminium hydrideLithium aluminium hydride, commonly abbreviated to LAH or known as LithAl, is an inorganic compound with the chemical formula LiAlH4. It was discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthesis, especially for the reduction of esters,...
and some other
hydrideIn chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
s.
-
Conversely, with some other catalysts, ethylene oxide may be
reduced by hydrogen to ethylene with the yield up to 70%. The reduction catalysts include mixtures of zinc dust and
acetic acidAcetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, of lithium aluminium hydride with titanium trichloride (the reducing agent is actually
titanium dichlorideTitanium chloride is the chemical compound with the formula TiCl2. The black solid has been studied only moderately, probably because of its high reactivity. Ti is a strong reducing agent: it has a high affinity for oxygen and reacts irreversibly with water to produce H2. The usual preparation is...
, formed by the reaction between LiAlH
4 and TiCl
2) and of
iron(III) chlorideIron chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula FeCl3. The colour of iron chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red...
with butyllithium in
tetrahydrofuranTetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
.
-
Oxidation
Ethylene oxide can further be oxidized, depending on the conditions, to
glycolic acidGlycolic acid is the smallest α-hydroxy acid . This colorless, odorless, and hygroscopic crystalline solid is highly soluble in water. It is used in various skin-care products. Glycolic acid is found in some sugar-crops...
or
carbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
:
-
Deep gas-phase reactor oxidation of ethylene oxide at 800–1000 K and a pressure of 0.1–1 MPa yields a complex mixture of products containing O
2, H
2,
COCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
,
CO2Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
,
CH4Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
,
C2H2Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
,
C2H4Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
,
C2H6Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane that is an aliphatic hydrocarbon. At standard temperature and pressure, ethane is a colorless, odorless gas....
,
C3H6Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...
,
C3H8Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...
and
CH3CHOAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
.
Dimerization
In the presence of acid catalysts, ethylene oxide can be dimerized into dioxane:
-
The reaction mechanism is as follows:
-
The dimerization reaction is not selective, and there are always by-products, such as
acetaldehydeAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
(due to isomerization). The selectivity and speed of dimerization can be increased by adding a catalyst, such as platinum, platinum-palladium or
iodineIodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
with sulfolan; however, 2-methyl-1,3-
dioxolaneDioxolane is a heterocyclic acetal with the chemical formula 2O2CH2. It is related to tetrahydrofuran by interchange of one oxygen for a CH2 group. The corresponding saturated 6-membered C4O2 rings are called dioxanes. The isomeric 1,2-dioxolane is an peroxide...
is formed as a side product in the last case.
Polymerization
Liquid ethylene oxide can form polyethyleneglycols. The polymerization can proceeds via radical and ionic mechanisms, but only the latter has a wide practical application.
Cationic polymerizationCationic polymerization is a type of chain growth polymerization in which a cationic initiator transfers charge to a monomer which becomes reactive. This reactive monomer goes on to react similarly with other monomers to form a polymer...
of ethylene oxide is assisted by protonic acids (
HClO4Perchloric acid is the inorganic compound with the formula HClO4. Usually encountered as an aqueous solution, this colourless compound is a strong acid comparable in strength to sulfuric and nitric acids. It is a powerful oxidizer, but its aqueous solutions up to appr. 70% are remarkably inert,...
,
HClHydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
), Lewis acids (
SnCl4Tin chloride, also known as tin tetrachloride or stannic chloride is a chemical compound with the formula SnCl4.At room temperature it is a colourless liquid, which fumes on contact with air, giving a stinging odor...
,
BF3Boron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...
, etc.), organometallic compounds or more complex reagents:
-
The reaction mechanism is as follows. At the first stage, the catalyst (MX
m) is initiated by alkyl-or acylhalogen or by compounds with active hydrogen atoms, usually water, alcohol or glycol:
- MXm + ROH → MXmRO–H+
The resulting active complex reacts with ethylene oxide via the
SN2 mechanism:
- (CH2CH2)O + MXmRO–H+ → (CH2CH2)O•••H+O–RMXm
- (CH2CH2)O•••H+ O–RMXm → HO–CH2CH2+ + MXmRO–2
- HO–CH2CH2+ + n (CH2CH2)O → HO–CH2CH2–(O–CH2CH2)n+
The chain breaks as
- HO–CH2CH2–(O–CH2CH2)n+ + MXmRO– → HO–CH2CH2–(O–CH2CH2)n–OR + MXm
- H(O–CH2CH2)n–O–CH2–CH2+ + MXmRO– → H(O–CH2CH2)n–O–CH=CH2 + MXm + ROH
Anionic polymerization of ethylene oxide is assisted by bases, such as
alcoholateAlcoholate can refer to:* the crystalline form of a salt in which alcohol takes the place of water of crystallization.* a tincture, or alcoholic extract of plant material.* an alkoxide, the salt of an alcohol....
s
hydroxideHydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
s,
carbonateIn chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
s or other compounds of alkali or
alkaline earth metalThe alkaline earth metals are a group in the periodic table. In the modern IUPAC nomenclature, the alkaline earth metals are called the group 2 elements. Previously, they were called the Group IIA elements . The alkaline earth metals contain beryllium , magnesium , calcium , strontium , barium and...
s. The reaction mechanism is as follows:
- (CH2CH2)O + RONa → RO–CH2CH2–O–Na+
- RO–CH2CH2–O–Na+ + n (CH2CH2)O → RO–(CH2CH2–O)n–CH2CH2–O–Na+
- RO–(CH2CH2–O)n–CH2CH2–O–Na+ → RO–(CH2CH2–O)n–CH=CH2 + NaOH
- RO–(CH2CH2–O)n–CH2CH2–O–Na+ + H2O → RO–(CH2CH2–O)(n+1)OH + NaOH
Thermal decomposition
Ethylene oxide is relatively stable to heating – in the absence of a catalyst, it does not dissociate up to 300 °C, and only above 570 °C there is a major
exothermicIn thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light , electricity , or sound...
decomposition, which proceeds through the radical mechanism. The first stage involves isomerization, however high temperature accelerated the radical processes. They result in a gas mixture containing acetaldehyde, ethane, ethyl, methane, hydrogen, carbon dioxide,
keteneA ketene is an organic compound of the form R'RC=C=O. The term is also used specifically to mean ethenone, the simplest ketene, where R' and R are hydrogen atoms.Ketenes were first studied as a class by Hermann Staudinger.-Formation:...
and
formaldehydeFormaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
. High-temperature
pyrolysisPyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...
(830–1200 K) at elevated pressure in an inert atmosphere leads to a more complex composition of the gas mixture, which also contains
acetyleneAcetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
and
propanePropane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...
. Contrary to the isomerization, initiation of the chain occurs mainly as follows:
- (CH2CH2)O → •CH2CH2O• → CH2O + CH2:
When carrying the thermal decomposition of ethylene oxide in the presence of transition metal compounds as catalysts, it is possible not only to reduce its temperature, but also to have
ethylEthyl may refer to:* Ethyl group, a functional group in organic chemistry* Ethyl Corporation, a fuel additive company* Ethanol, also known as ethyl alcohol* Cold Ethyl, a rock band founded by Nicke Andersson...
as the main product, that is to reverse the ethylene oxide synthesis reaction.
Other reactions
ThiocyanateThiocyanate is the anion [SCN]−. It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Organic compounds containing the functional group SCN are also called thiocyanates...
ions or
thioureaThiourea is an organosulfur compound of with the formula SC2 . It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. "Thioureas" refers to a broad...
transform ethylene oxide into
thiiraneThiirane, more commonly known as ethylene sulfide, is the cyclic chemical compound with the formula C2H4S. It is the smallest sulfur-containing heterocycle. Like many organosulfur compounds, this species has a stench. Thiirane is also used to describe any derivative of the parent ethylene...
s (ethylene sulfides):
- (CH2CH2)O + (NH2)2C=S → (CH2CH2)S + (NH2)2C=O
-
Reaction of phosphorus pentachloride with ethylene oxide produces ethylene dichloride:
- (CH2CH2)O + PCl5 → Cl–CH2CH2–Cl + POCl3
Other dichloro derivatives of ethylene oxide can be obtained by combined action of
sulfuryl chlorideSulfuryl chloride is an inorganic compound with the formula SO2Cl2. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature, as can be inferred from its rapid hydrolysis....
(SOCl
2) and
pyridinePyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
and of
triphenylphosphineTriphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...
and
carbon tetrachlorideCarbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...
.
Phosphorus trichloridePhosphorus trichloride is a chemical compound of phosphorus and chlorine, having chemical formula PCl3. Its shape is trigonal pyramidal. It is the most important of the three phosphorus chlorides. It is an important industrial chemical, being used for the manufacture of organophosphorus compounds...
reacts with ethylene oxide forming chloroethyl esters of phosphorous acid:
- (CH2CH2)O + PCl3 → Cl–CH2CH2–OPCl2
- 2 (CH2CH2)O + PCl3 → (Cl–CH2CH2–O)2PCl
- 3 (CH2CH2)O + PCl3 → Cl–CH2CH2–O)3P
The reaction product of ethylene oxide with
acyl chlorideIn organic chemistry, an acyl chloride is an organic compound with the functional group -CO-Cl. Their formula is usually written RCOCl, where R is a side chain. They are usually considered to be reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride,...
s in the presence of
sodium iodideSodium iodide is a white, crystalline salt with chemical formula NaI used in radiation detection, treatment of iodine deficiency, and as a reactant in the Finkelstein reaction.-Uses:Sodium iodide is commonly used to treat and prevent iodine deficiency....
is a complex iodoethyl ether:
- (CH2CH2)O + RCOCl + NaI → RC(O)–OCH2CH2–I + NaCl
Heating ethylene oxide to 100 °C with
carbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, in a non-polar solvent in the presence of
bis-(triphenylphosphine)-nickel(0) results in
ethylene carbonateEthylene carbonate is an ester of ethylene glycol and carbonic acid. At room temperature ethylene carbonate is a transparent crystalline solid, practically odorless and colorless, and somewhat soluble in water. In the liquid state Ethylene carbonate is an ester of ethylene glycol and carbonic...
:
-
In industry, a similar reaction is carried out at high pressure and temperature in the presence of quaternary ammonium or phosphonium salts as a catalyst.
Reaction of ethylene oxide with
formaldehydeFormaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
at 80–150 °C in the presence of a catalyst leads to the formation of
1,3-dioxolaneDioxolane is a heterocyclic acetal with the chemical formula 2O2CH2. It is related to tetrahydrofuran by interchange of one oxygen for a CH2 group. The corresponding saturated 6-membered C4O2 rings are called dioxanes. The isomeric 1,2-dioxolane is an peroxide...
:
-
Substituting formaldehyde by other aldehydes or ketones results in a 2-substituted 1,3-dioxolane (yield: 70–85%, catalyst: tetraetilammoniybromid).
Catalytic
hydroformylationHydroformylation, also known as oxo synthesis or oxo process, is an important industrial process for the production of aldehydes from alkenes. This chemical reaction entails the addition of a formyl group and a hydrogen atom to a carbon-carbon double bond...
of ethylene oxide results in hydroxypropanal and further in propane-1,3-diol:
-
Dehydrochlorination of ethylene and its derivatives
Dehydrochlorination of
2-chloroethanol2-Chloroethanol is an organochlorine compound with the formula HOCH2CH2Cl. This colorless liquid has a pleasant ether-like odor. It is miscible with water...
, developed by Wurtz back in 1859, still remains one of the most common laboratory methods of producing ethylene oxide:
- Cl–CH2CH2–OH + NaOH → (CH2CH2)O + NaCl + H2O
The reaction is carried out at elevated temperature, and beside
sodium hydroxide or
potassium hydroxidePotassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
,
calcium hydroxideCalcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or...
,
barium hydroxideBarium hydroxide is the chemical compound with the formula Ba2. Also known as baryta, it is one of the principal compounds of barium. The white granular monohydrate is the usual commercial form.-Preparation:...
,
magnesium hydroxideMagnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite....
or
carbonateIn chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
s of alkali or alkaline earth metals can be used.
Chloroethanol, in turn, is synthesized using one of the following methods:
- By reacting ethylene glycol with hydrochloric acid:
-
- HO–CH2CH2–OH + HCl → HO–CH2CH2–Cl + H2O
- By reacting ethylene with hypochlorous acid
Hypochlorous acid is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor...
:
-
- CH2=CH2 + HOCl → HO–CH2CH2–Cl
- By chlorination of ethylene:
-
- CH2=CH2 + Cl2 + H2O → HO–CH2CH2–Cl + HCl
Another convenient and old method of ethylene oxide synthesis is reaction of an
alkaliIn chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...
with chloroethyl acetate:
- Cl–CH2CH2–OCOCH3 + 2 KOH → (CH2CH2)O + KCl + CH3COOK + H2O
With a high yield (90%) ethylene oxide can be produced by reacting
calcium oxideCalcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....
with ethyl hypochlorite; substituting calcium by other alkaline earth metals reduces the reaction yield:
- 2 CH3CH2–OCl + CaO → 2 (CH2CH2)O + CaCl2 + H2O
In turn, ethylhypochlorite is synthesized as follows:
- Cl2 + NaOH + CH3CH2OH → CH3CH2OCl + NaCl + H2O
Direct oxidation of ethylene by peroxy acids
Ethylene can be directly oxidized into ethylene oxide using
peroxy acidA peroxy acid is an acid which contains an acidic -OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the organic derivatives of carboxylic acids...
s, for example,
peroxybenzoicPeroxybenzoic acid is a simple peroxy acid. It may be synthesized from benzoic acid and hydrogen peroxide, or by the treatment of benzoyl peroxide with sodium methoxide, followed by acidification....
or
meta-chloro-peroxybenzoic acid:
-
Oxidation by peroxy acids is efficient for higher alkenes, but not for ethylene. The above reaction is slow and has low yield, therefore it is not used in the industry.
Other preparative methods
Other synthesis methods include reaction of diiodo ethane with silver oxide:
- I–CH2CH2–I + Ag2O → (CH2CH2)O + 2 AgI
and decomposition of ethylene carbonate at 200–210 °C in the presence of
hexachloroethaneHexachloroethane, also known as perchloroethanes , C2Cl6, is a colorless solid at room temperature which is used by the US Military in smoke compositions, e.g...
:
-
History
Commercial production of ethylene oxide dates back to 1914 when
BASFBASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...
built the first factory which used the chlorohydrin process (reaction of ethylene chlorohydrin with calcium hydroxide). The chlorohydrin process was unattractive for several reasons, including low efficiency and loss of valuable chlorine into
calcium chlorideCalcium chloride, CaCl2, is a salt of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. Common applications include brine for refrigeration plants, ice and dust control on roads, and desiccation...
. More efficient direct oxidation of ethylene by air was invented by Lefort in 1931 and in 1937
Union CarbideUnion Carbide Corporation is a wholly owned subsidiary of The Dow Chemical Company. It currently employs more than 2,400 people. Union Carbide primarily produces chemicals and polymers that undergo one or more further conversions by customers before reaching consumers. Some are high-volume...
opened the first plant using this process. It was further improved in 1958 by Shell Oil Co. by replacing air with oxygen and using elevated temperature of 200–300 °C and pressure (1–3 MPa). This more efficient routine accounted for about half of ethylene oxide production in the 1950s in the U.S., and after 1975 it completely replaced the previous methods.
Chlorohydrin process of production of ethylene oxide
Although the chlorohydrin process is almost entirely superseded in the industry by the direct oxidation of ethylene, the knowledge of this method is still important for educational reasons and because it is still used in the production of
propylene oxidePropylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics...
. The process consists of three major steps: synthesis of ethylene chlorohydrin, dehydrochlorination of ethylene chlorohydrin to ethylene oxide and purification of ethylene oxide. Those steps are carried continuously. In the first column, hypochlorination of ethylene is carried out as follows:
- Cl2 + H2O → HOCl + HCl
- CH2=CH2 + HOCl → OH–CH2CH2–Cl
- CH2=CH2 + Cl2 → Cl–CH2CH2–Cl
To suppress the conversion of ethylene into the ethylene dichloride (the last reaction), the concentration of ethylene is maintained at about 4–6%, and the solution is heated by steam to the boiling point.
Next, aqueous solution of ethylene chlorohydrin enters the second column, where it reacts with a 30% solution of calcium hydroxide at 100 °C:
- 2 OH–CH2CH2–Cl + Ca(OH)2 → 2 (CH2CH2)O + CaCl2 + H2O
The produced ethylene oxide is purified by
rectificationA rectified spirit, rectified alcohol, or neutral spirit is highly concentrated ethanol which has been purified by means of repeated distillation, a process that is called rectification. It typically contains 95% alcohol by volume...
. The chlorohydrin process allows to reach 95% conversion of ethylene chlorohydrin. The yield of ethylene oxide is about 80% of the theoretical value; for 1 ton of ethylene oxide, about 200 kg of ethylene dichloride is produced.
Usage in global industry
Direct oxidation of ethylene was patented by Lefort in 1931. This method was repeatedly modified for industrial use, and at least four major variations are known. They all use oxidation by oxygen or air and a silver-based catalyst, but differ in the technological details and hardware implementations.
Union CarbideUnion Carbide Corporation is a wholly owned subsidiary of The Dow Chemical Company. It currently employs more than 2,400 people. Union Carbide primarily produces chemicals and polymers that undergo one or more further conversions by customers before reaching consumers. Some are high-volume...
(currently a division of
Dow Chemical CompanyThe Dow Chemical Company is a multinational corporation headquartered in Midland, Michigan, United States. As of 2007, it is the second largest chemical manufacturer in the world by revenue and as of February 2009, the third-largest chemical company in the world by market capitalization .Dow...
) was the first company to develop the direct oxidation process. Since 1994, it uses the so-called METEOR process (
Most
Effective
Technology for
Ethylene
Oxide
Reactions) which is characterized by high productivity, low initial capital investment and low operating costs. The method is the exclusive property of the company; it is used only at its own plants and accounts for about 20% of the global ethylene oxide production.
A similar production method was developed by Scientific Design Co., but it received wider use because of the licensing system – it accounts for 25% of the world's production and for 75% of world's licensed production of ethylene oxide. A proprietary variation of this method is used by Japan Catalytic Chemical Co., which adapted synthesis of both ethylene oxide and ethylene glycol in a single industrial complex.
A different modification was developed Shell International Chemicals BV. Their method is rather flexible with regard to the specific requirements of specific industries; it is characterized by high selectivity with respect to the ethylene oxide product and long lifetime of the catalyst (3 years). It accounts for about 40% of global production.
Older factories typically use air for oxidation whereas newer plants and processes, such as METEOR and Japan Catalytic, favor oxygen.
Chemistry and kinetics of the direct oxidation process
Formally, the direct oxidation process is expressed by the following equation:
-
However, significant yield of carbon dioxide and water is observed in practice, which can be explained by the complete oxidation of ethylene or ethylene oxide:
- CH2=CH2 + 3 O2 → 2 CO2 + 2 H2O
- 2 (CH2CH2)O + 5 O2 → 4 CO2 + 4 H2O
The process of heterogeneous catalytic oxidation of ethylene was studied by P. A. Kilty and W. M. H. Sachtler, who suggested the following mechanism:
- O2 + 4 Ag(adj) → 4 Ag + 2 O2–(ads)
- O2 + Ag → Ag+ + O2–
- O2–(ads) + CH2=CH2 → (CH2CH2)O + O(ads)
- 6 O (ads) + CH2=CH2 → 2 CO2 + 2 H2O
Here (ads) refers to particles adsorbed on the catalyst surface and (adj) to particles of silver, directly adjacent to the oxygen atoms.
Thus the overall reaction is expressed as
- 7 CH2=CH2 + 6 O2 → 6 (CH2CH2)O + 2 CO2 + 2 H2O
and the maximum degree of conversion of ethylene to ethylene oxide is 6/7 or 85.7%.
The catalyst for the reaction is metallic silver deposited on various matrixes, including
pumicePumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
,
silica gelSilica gel is a granular, vitreous, porous form of silica made synthetically from sodium silicate. Despite its name, silica gel is a solid. It is a naturally occurring mineral that is purified and processed into either granular or beaded form...
, various
silicateA silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
s and
aluminosilicateAluminosilicate minerals are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals....
s, alumina and
silicon carbideSilicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
, and activated by certain additives (
antimonyAntimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
,
bismuthBismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
,
barium peroxideBarium peroxide is the chemical compound with the formula BaO2. This grey-white solid is one of the most common inorganic peroxides. Barium peroxide is an oxidizing agent, which is used for bleaching...
, etc.). The process temperature was optimized as 220–280 °C. Lower temperatures reduce the activity of the catalyst, and higher temperatures promote the complete oxidation of ethylene thereby reducing the yield of ethylene oxide. Elevated pressure of 1–3 MPa increases the productivity of the catalyst and facilitates absorption of ethylene oxide from the reacting gases.
Whereas oxidation by air is still being used, oxygen (> 95% purity) is preferred for several reasons, such as higher molar yield of ethylene oxide (75–82% for oxygen vs. 63–75% for air), higher reaction rate (no gas dilution) and no need of separating nitrogen in the reaction products.
World production of ethylene oxide
The world production of ethylene oxide was 19 million tonnes in 2008 and 18 million tonnes in 2007. This places ethylene oxide 14th most produced organic chemical, whereas the most produced one was ethylene with 113 million tonnes. SRI Consulting forecasted the growth of consumption of ethylene oxide of 4.4% per year during 2008–2013 and 3% from 2013 to 2018.
In 2004, the global production of ethylene oxide by region was as follows:
! Align = "center" width = 40%|Region
! Align = "center" width = 30%|Number of major producers
! Align = "center" width = 30%|Production, thousand tonnes>
|
|
North America United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
MexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
>
10
3
3 |
4009
1084
350 |
|
|
South America BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
VenezuelaVenezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
>
2
1 |
312
82 |
|
|
Europe BelgiumBelgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
FranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
GermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
NetherlandsThe Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
SpainSpain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
TurkeyTurkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
United KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
Eastern EuropeEastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...
>
2
1
4
2
1
1
1
no data |
770
215
995
460
100
115
300
950 |
|
|
Middle East IranIran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
KuwaitThe State of Kuwait is a sovereign Arab state situated in the north-east of the Arabian Peninsula in Western Asia. It is bordered by Saudi Arabia to the south at Khafji, and Iraq to the north at Basra. It lies on the north-western shore of the Persian Gulf. The name Kuwait is derived from the...
Saudi ArabiaThe Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...
>
2
1
2 |
201
350
1781 |
|
|
Asia ChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
TaiwanTaiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
IndonesiaIndonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
JapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
Malaysia South KoreaThe Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...
SingaporeSingapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
>
No data
4
2
1
4
1
3
1 |
The world's largest producers of ethylene oxide are
Dow Chemical CompanyThe Dow Chemical Company is a multinational corporation headquartered in Midland, Michigan, United States. As of 2007, it is the second largest chemical manufacturer in the world by revenue and as of February 2009, the third-largest chemical company in the world by market capitalization .Dow...
(3–3.5 million tonnes in 2006),
Saudi Basic IndustriesSABIC is a diversified manufacturing company, active in chemicals and intermediates, industrial polymers, fertilizers and metals. It is the largest public company in Saudi Arabia as listed in Tadawul, but the Saudi government still owns 70% of its shares...
(2000–2500 tonnes in 2006),
Royal Dutch ShellRoyal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six...
(1.328 million tonnes in 2008–2009),
BASFBASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...
(1.175 million tonnes in 2008–2009),
China Petrochemical CorporationChina Petrochemical Corporation or Sinopec Group is Asia's largest oil refining and petrochemical enterprise, administered by SASAC for the State Council of the People's Republic of China...
(~1000 tonnes in 2006),
Formosa PlasticsFormosa Plastics Corporation is a Taiwanese company based in Taiwan that primarily produces polyvinyl chloride resins and other intermediate plastic products. It is the corporation around which influential businessman Wang Yung-ching formed the Formosa Plastics Group, and it remains central to...
(~1 million tonnes in 2006) and
IneosINEOS Group Limited is a privately owned multinational chemicals company headquartered in Lausanne, Switzerland and with its registered office in Lyndhurst, United Kingdom...
(0.92 million tonnes in 2008–2009).
Applications
Ethylene oxide is one of the most important raw materials used in the large-scale chemical production. Most ethylene oxide is used for synthesis of
ethylene glycolEthylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
s, including diethylene glycol and triethylene glycol, that accounts for up to 75% of global consumption. Other important products include ethylene glycol ethers, ethanolamines and ethoxylates. Among glycols, ethylene glycol is used as
antifreezeAntifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....
, in the production of
polyesterPolyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...
and
polyethylene terephthalatePolyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
(PET – raw material for plastic bottles), liquid coolants and solvents. Polyethyleneglycols are used in perfumes, cosmetics, pharmaceuticals,
lubricantA lubricant is a substance introduced to reduce friction between moving surfaces. It may also have the function of transporting foreign particles and of distributing heat...
s,
paint thinnerA paint thinner is a solvent used to thin oil-based paints or clean up after their use, although all such solvents have other uses. Commercially, "paint thinner" is usually a name for mineral spirits.Products used as paint thinners include:*Mineral spirits...
s and
plasticizerPlasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
s. Ethylene glycol ethers are part of brake fluids, detergents, solvents, lacquers and paints. Other products of ethylene oxide. Ethanolamines are used in the manufacture of soap and detergents and for purification of natural gas. Ethoxylates are reaction products of ethylene oxide with higher alcohols, acids or amines. They are used in the manufacture of detergents, surfactants, emulsifiers and
dispersantA dispersant or a dispersing agent or a plasticizer or a superplasticizer is either a non-surface active polymer or a surface-active substance added to a suspension, usually a colloid, to improve the separation of particles and to prevent settling or clumping...
s.
Whereas synthesis of ethylene glycols is the major application of ethylene oxide, its percentage varies greatly depending on the region: from 44% in the
Western EuropeWestern Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...
, 63% in
JapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and 73% in
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
to 90% in the rest of
AsiaAsia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
and 99% in
AfricaAfrica is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
.
Production of ethylene glycol
Ethylene glycol is industrially produced by non-catalytic hydration of ethylene oxide at a temperature of 200 °C and a pressure of 1.5–2 MPa:
- (CH2CH2)O + H2O → HOCH2CH2OH
By-products of the reaction are diethylene glycol, triethylene glycol and polyglycols with the total of about 10%, which are separated from the ethylene glycol by distillation at reduced pressure.
Another synthesis method is the reaction of ethylene oxide and CO
2 (temperature 80–120 °C and pressure of 5.2 MPa) yielding
ethylene carbonateEthylene carbonate is an ester of ethylene glycol and carbonic acid. At room temperature ethylene carbonate is a transparent crystalline solid, practically odorless and colorless, and somewhat soluble in water. In the liquid state Ethylene carbonate is an ester of ethylene glycol and carbonic...
and its subsequent hydrolysis with decarboxylation:
-
Modern technologies of production of ethylene glycol include the following. Shell OMEGA technology (Only Mono-Ethylene Glycol Advantage) is a two-step synthesis of ethylene carbonate using a
phosphoniumThe phosphonium cation describes positively charged polyatomic cations with the chemical formula . Salts of the parent PH4+ are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakisphosphonium chloride:Organic phosphonium salts are common...
halide as a catalyst. The glycol yield is 99–99.5%, with other glycols practically absent. The main advantage of the process is production of pure ethylene glycol without the need for further purification. The first commercial plant which uses this method was opened in 2008 in South Korea. Dow METEOR (Most Effective Technology for Ethylene Oxide Reactions) is an integrated technology for producing ethylene oxide and its subsequent hydrolysis into ethylene glycol. The glycol yield is 90–93%. The main advantage of the process is relative simplicity, using fewer stages and less equipment.
Production of glycol ethers
The major industrial esters of mono-, di- and triethylene glycols are methyl, ethyl and normal butyl ethers, as well as their acetates and phthalates. The synthesis involves reaction of the appropriate
alcoholIn chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
with ethylene oxide:
- (CH2CH2)O + ROH → HOCH2CH2OR
- (CH2CH2)O + HOCH2CH2OR → HOCH2CH2OCH2CH2OR
- (CH2CH2)O + HOCH2CH2OCH2CH2OR → HOCH2CH2OCH2CH2OCH2CH2OR
The reaction of monoesters with an acid or its anhydride leads to the formation of the esters:
- CH3COOH + HOCH2CH2OR → ROCH2CH2OCOCH3 + H2O
Production of ethanolamines
In the industry,
ethanolamineEthanolamine, also called 2-aminoethanol or monoethanolamine , is an organic chemical compound that is both a primary amine and a primary alcohol . Like other amines, monoethanolamine acts as a weak base...
s (mono-, di- and triethanolamines) are produced by reacting
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
and ethylene oxide in anhydrous medium at a temperature of 40–70 °C and pressure of 1.5–3.5 MPa:
O + NH
3 → HOCH
2CH
2NH
2
- 2 (CH2CH2)O + NH3 → (HOCH2CH2)2NH
- 3 (CH2CH2)O + NH3 → (HOCH2CH2)3N
All three ethanolamines are produced in the process, while ammonia and part of methylamine are recycled. The final products are separated by vacuum
distillationDistillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
. Hydroxyalkylamines are produced in a similar process:
O + RNH
2 → HOCH
2CH
2NHR
- 2 (CH2CH2)O + RNH2 → (HOCH2CH2)2NR
Monosubstituted products are formed by reacting a large excess of amine with ethylene oxide in presence of water and at a temperature below 100 °C. Disubstituted products are obtained with a small excess of ethylene oxide, at a temperature of 120–140 °C and a pressure of 0.3–0.5 MPa.
Production of ethoxylates
Industrial production of ethoxylates is realized by a direct reaction of higher alcohols, acids or amines with ethylene oxide in the presence of an alkaline catalyst at a temperature of 120–180 °C. Modern plants producing ethoxylates are usually based on the BUSS LOOP reactors technology, which is based on a three-stage continuous process. In the first stage, the initiator or catalyst of the reaction and the feedstock are fed into the container, where they are mixed, heated and vacuum dried. Then reaction is carried out in a special insulated reactor in an inert atmosphere (nitrogen) to prevent a possible explosion of ethylene oxide. Finally, the reaction mixture is neutralized, degassed and purified.
Production of acrylonitrile
Currently, most
acrylonitrileAcrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...
(90% in 2008) is produced by the SOHIO method, which is based on the catalytic oxidation of
propylenePropene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...
in the presence of ammonia and bismuth phosphomolybdate. However, until 1960 a key production process was addition of
hydrogen cyanide to ethylene oxide, followed by dehydration of the resulting
cyanohydrinA cyanohydrin is a functional group found in organic compounds. Cyanohydrins have the formula R2CCN, where R is H, alkyl, or aryl. Cyanohydrins are industrially important precursors to carboxylic acids and some amino acids...
::
-
Addition of hydrocyanic acid to ethylene oxide is carried out in the presence of a catalyst (
sodium hydroxide and
diethylamineDiethylamine is a secondary amine with the molecular structure CH3CH2NHCH2CH3. It is a flammable, strongly alkaline liquid. It is miscible with water and ethanol. It is a colorless liquid which often appears brown due to impurities...
), and dehydration of cyanohydrin occurs in the gas phase upon the catalytic action of
aluminium oxideAluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...
.
Other uses
The direct use of ethylene oxide accounts for only 0.05% (2004 data) of its global production. Ethylene oxide is used as a
fumigantFumigation is a method of pest control that completely fills an area with gaseous pesticides—or fumigants—to suffocate or poison the pests within. It is utilized for control of pests in buildings , soil, grain, and produce, and is also used during processing of goods to be imported or...
and disinfecting agent, as a mixture with carbon dioxide (8.5–80% of ethylene oxide), nitrogen or
dichlorodifluoromethaneDichlorodifluoromethane , is a colorless gas, and usually sold under the brand name Freon-12, is a chlorofluorocarbon halomethane , used as a refrigerant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was banned in the United States along with many other...
(12% ethylene oxide). It is applied for gas-phase sterilization of medical equipment and instruments, packaging materials and clothing, surgical and scientific equipment; for processing of storage facilities (tobacco, packages of grain, sacks of rice, etc.), clothing, furs and valuable documents.
Ethylene oxide is used as an accelerator of maturation of tobacco leaves and
fungicideFungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
. Ethylene oxide is also used as a main component of
thermobaric weaponA thermobaric weapon, which includes the type known as a "fuel-air bomb", is an explosive weapon that produces a blast wave of a significantly longer duration than those produced by condensed explosives. This is useful in military applications where its longer duration increases the numbers of...
s (fuel-air explosives).
Identification of ethylene oxide
The simplest qualitative reaction for ethylene oxide uses its property to precipitate insoluble hydroxides of metals when it is passed through aqueous solutions of their salts, for example
- 2 (CH2CH2)O + MnCl2 + 2 H2O → 2 HO–CH2CH2–Cl + Mn(OH)2↓
Similarly, ethylene oxide is detected by the bright pink color of the indicator when passing air through aqueous solutions of some salts of sodium or potassium (chlorides, iodides, thiosulfates, etc.) with the addition of
phenolphthaleinPhenolphthalein is a chemical compound with the formula C20H14O4 and is often written as "HIn" or "phph" in shorthand notation. Often used in titrations, it turns colorless in acidic solutions and pink in basic solutions...
:
- (CH2CH2)O + NaCl + H2O → HO–CH2CH2–Cl + NaOH
Other methods of ethylene oxide detection are color reactions with
pyridinePyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
derivatives and hydrolysis of ethylene glycol with
periodic acidPeriodic acid, or iodic acid is an oxoacid of iodine having chemical formula HIO4 or H5IO6.In dilute aqueous solution, periodic acid exists as discrete hydronium and metaperiodate ions. When more concentrated, orthoperiodic acid, H5IO6, is formed; this dissociates into hydronium and...
. The produced
iodic acidIodic acid, HIO3, can be obtained as a white solid. It dissolves in water very well, but it also exists in the pure state, as opposed to chloric acid or bromic acid. Iodic acid contains iodine in the oxidation state +5 and it is one of the most stable oxo-acids of the halogens in its pure state....
is detected with
silver nitrateSilver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides...
.
The main physical method of ethylene oxide detection is gas chromatography.
Fire and explosion hazards
Ethylene oxide is extremely flammable and its mixtures with air are explosive. When heated, it may rapidly expand causing fire and explosion. The
autoignition temperatureThe autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion...
is 429 °C, minimum inflammable content in the air is 2.7%, and the NPFA rating is
NFPA 704NFPA 704 is a standard maintained by the U.S.-based National Fire Protection Association. It defines the colloquial "fire diamond" used by emergency personnel to quickly and easily identify the risks posed by nearby hazardous materials...
.
Fires caused by ethylene oxide are extinguished by traditional media, including foam, carbon dioxide or water. Extinguishing of burning ethylene oxide is complicated by that it can continue burning in an inert atmosphere and in water solutions. Fire suppression is reached only upon dilution with water above 22:1.
Effect on microorganisms
Ethylene oxide inhibits growth of microorganisms (
disinfectant propertiesDisinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially nonresistant bacterial spores; it is less effective than sterilisation, which is an extreme physical...
) and when present in high concentrations, can completely destroy them. Strong alkylating properties make ethylene oxide a universal poison for
protoplasmProtoplasm is the living contents of a cell that is surrounded by a plasma membrane. It is a general term of the Cytoplasm . Protoplasm is composed of a mixture of small molecules such as ions, amino acids, monosaccharides and water, and macromolecules such as nucleic acids, proteins, lipids and...
: it causes clotting of proteins, deactivation of
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s and other biologically important components of a living organism.
Ethylene oxide acts more strongly against bacteria, especially gram-positive bacteria, than against
yeastYeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
and fungi. The disinfectant effect of ethylene oxide is similar to that of sterilization by heat, but because of limited penetration, it affects only the surface. The Sterility Assurance Level, after a certain specified exposure to ethylene oxide is 10
−6, meaning that the chance of finding a single bacterium is below 1 per million.
Effects on humans and animals
Ethylene oxide is an
alkylating agentAlkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...
; it has irritating, sensitizing and narcotic effects. Chronic exposure to ethylene oxide also induces
mutagenic effectsIn genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are therefore also likely to be carcinogens...
. The
International Agency for Research on CancerThe International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....
classifies ethylene oxide into group 1, meaning it is a proven
carcinogenA carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
. A 2003 study of 7,576 women exposed while at work in commercial sterilization facilities in the U.S. suggests ethylene oxide is associated with
breast cancerBreast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
incidence. A 2004 follow up study analyzing 18,235 men and women workers exposed to ethylene oxide from 1987 to 1998 concluded "There was little evidence of any excess cancer mortality for the cohort as a whole, with the exception of bone cancer based on small numbers. Positive exposure-response trends for lymphoid tumors were found for males only. Reasons for the sex specificity of this effect are not known. There was also some evidence of a positive exposure-response for breast cancer mortality."
Ethylene oxide is toxic by inhalation with an U.S.
OSHAThe United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
permissible exposure limit of 1 ppm calculated as a time weighted average (TWA) over 8 hours of 1 ppm, and a short term exposure limit (excursion limit) calculated as a TWA over 15 minutes of 5 ppm. [29 CFR 19101.1048]. At concentrations in the air about 200 parts per million, ethylene oxide irritates
mucous membraneThe mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...
s of the nose and throat; higher contents cause damage to the trachea and bronchi, progressing into the partial collapse of the lungs. High concentrations can cause
pulmonary edemaPulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
and damage the cardiovascular system; the damaging effect of ethylene oxide may occur only after 72 hours after exposure. The maximum content of ethylene oxide in the air according to the U.S. standards (
ACGIHThe American Conference of Governmental Industrial Hygienists is a professional association of industrial hygienists and practitioners of related professions, with headquarters in Cincinnati, Ohio...
) is 1.8 mg/m
3.
NIOSHThe National Institute for Occupational Safety and Health is the United States’ federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention within the U.S...
has determined that the Immediately Dangerous to Life and Health level (IDLH) is 800 ppm.
Because the odor threshold for ethylene oxide varies between 250 and 700 ppm, the gas will already be at toxic concentrations when it can be smelled. Even then, the odor of ethylene oxide is sweet, aromatic, and can easily be mistaken for the pleasant aroma of
diethyl etherDiethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
, a common laboratory solvent of very low toxicity. In view of these insidious warning properties, continuous electrochemical monitors are standard practice, and it is forbidden to use ethylene oxide to fumigate building interiors in the EU and some other jurisdictions.
Ethylene oxide causes acute poisoning, accompanied by the following symptoms: slight heartbeat, muscle twitching, flushing, headache, diminished hearing,
acidosisAcidosis is an increased acidity in the blood and other body tissue . If not further qualified, it usually refers to acidity of the blood plasma....
, vomiting, dizziness, transient loss of consciousness and a sweet taste in the mouth. Acute intoxication is accompanied by a strong throbbing headache, dizziness, difficulty in speech and walking, sleep disturbance, pain in the legs, weakness, stiffness, sweating, increased muscular irritability, transient spasm of retinal vessels, enlargement of the liver and suppression of its antitoxic functions.
Ethylene easily penetrates through the clothing and footwear, causing skin irritation and dermatitis with the formation of blisters, fever and
leukocytosisLeukocytosis is a raised white blood cell count above the normal range in the blood. It is frequently a sign of an inflammatory response, most commonly the result of infection, and is observed in certain parasitic infections...
.
The median lethal doses (LD
50, or a dose required to kill half the members of a tested population after a certain time) for ethylene oxide are 72 mg/kg (rat, oral) and 187 mg/kg (rat,
subcutaneousThe hypodermis, also called the hypoderm, subcutaneous tissue, or superficial fascia is the lowermost layer of the integumentary system in vertebrates. Types of cells that are found in the hypodermis are fibroblasts, adipose cells, and macrophages...
injection).
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