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A diol or glycol is a chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 containing two hydroxyl groups (-OH groups) Vicinal
Vicinal (chemistry)

In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not....
 diols have hydroxyl groups attached to adjacent atoms. Examples of vicinal diol compounds are ethylene glycol
Ethylene glycol

Ethylene glycol is an alcohol with two -OH groups , a chemical compound widely used as an automobile antifreeze. In its pure form, it is an odorless, colorless, syrupy, sweet tasting, toxic liquid....
 and propylene glycol
Propylene glycol

Propylene glycol, known also by the systematic name propane-1,2-diol, is an organic compound , usually a faintly sweet, and colorless clear viscous liquid that is hygroscopic and miscible with water, acetone, and chloroform....
. Geminal
Geminal

In chemistry, the term geminal refers to the relationship between two functional groups that are attached to the same atom. The prefix gem is applied to a chemical name to denote this relationship, as in a gem-dibromide....
 diols have hydroxyl groups bonded to the same atom. In general, organic geminal diols readily dehydrate
Dehydration reaction

In chemistry, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions....
 to form a carbonyl group. For example, carbonic acid
Carbonic acid

Carbonic acid has the Molecular formula H2CO3. It is also a name sometimes given to solutions of carbon dioxide in water , which contain small amounts of H2CO3....
 ((HO)2C=O) is unstable and has a tendency to convert to carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 (CO2) and water (H2O).






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A diol or glycol is a chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
 containing two hydroxyl groups (-OH groups) Vicinal
Vicinal (chemistry)

In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not....
 diols have hydroxyl groups attached to adjacent atoms. Examples of vicinal diol compounds are ethylene glycol
Ethylene glycol

Ethylene glycol is an alcohol with two -OH groups , a chemical compound widely used as an automobile antifreeze. In its pure form, it is an odorless, colorless, syrupy, sweet tasting, toxic liquid....
 and propylene glycol
Propylene glycol

Propylene glycol, known also by the systematic name propane-1,2-diol, is an organic compound , usually a faintly sweet, and colorless clear viscous liquid that is hygroscopic and miscible with water, acetone, and chloroform....
. Geminal
Geminal

In chemistry, the term geminal refers to the relationship between two functional groups that are attached to the same atom. The prefix gem is applied to a chemical name to denote this relationship, as in a gem-dibromide....
 diols have hydroxyl groups bonded to the same atom. In general, organic geminal diols readily dehydrate
Dehydration reaction

In chemistry, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions....
 to form a carbonyl group. For example, carbonic acid
Carbonic acid

Carbonic acid has the Molecular formula H2CO3. It is also a name sometimes given to solutions of carbon dioxide in water , which contain small amounts of H2CO3....
 ((HO)2C=O) is unstable and has a tendency to convert to carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 (CO2) and water (H2O). Nevertheless, in rare situations the chemical equilibrium
Chemical equilibrium

In a chemical process, chemical equilibrium is the state in which the Activity or concentrations of the reactants and products have no net change over time....
 is in favor of the geminal diol. For example, when formaldehyde
Formaldehyde

Formaldehyde is a chemical compound with the chemical formula H2CO. It is the simplest aldehyde. Formaldehyde exists in several forms aside from H2CO: the cyclic trimer trioxane and the polymer Polyoxymethylene....
 (H2C=O) is dissolved in water
Water (molecule)

File:Blue-water-pool.jpgWater is the most abundant molecule on Earth's surface, constituting about 70% of the Earth's surface in liquid, solid, and gaseous states....
 the geminal diol (H2C(OH)2), methanediol
Methanediol

Methanediol, also known as formaldehyde monohydrate or methylene glycol, is a chemical compound that occurs primarily as the product of formaldehyde in water solution....
, is favored.

Examples of diols in which the hydroxyl functional groups are more widely separated include 1,4-butanediol
1,4-Butanediol

1,4-Butanediol is the organic compound with the chemical formula HOCH2CH2CH2CH2OH. This colorless viscosity liquid is derived from butane by placement of alcohol groups at each end of the chain....
 and bisphenol A
Bisphenol A

Bisphenol A, commonly abbreviated as BPA, is an organic compound with two phenol functional groups. It is a difunctional building block of several important plastics and plastic additives....
.

Synthesis of diols

Because diols are a common functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
 arrangement, numerous methods of preparation have been developed.
  • Vicinal diols can be produced from the oxidation of alkene
    Alkene

    In organic chemistry, an alkene, olefin, or olefine is an Saturation chemical compound containing at least one carbon-to-carbon double bond....
    s, usually with dilute acidic potassium permanganate
    Potassium permanganate

    Potassium permanganate is the inorganic chemical compound potassiummanganeseoxygen4, a water soluble salt consisting of equal Mole amounts of potassium and permanganate ions....
    , also known as potassium manganate(VII). Using alkaline potassium manganate(VII) produces a colour change from clear deep purple to clear green; acidic potassium manganate(VII) turns clear colourless.
  • Osmium tetroxide can similarly be used to oxidize alkenes to vicinal diols.
  • hydrogen peroxide
    Hydrogen peroxide

    Hydrogen peroxide is a very pale blue liquid which appears colorless in a dilute solution, slightly more viscous than water. It is a weak acid....
     reacts with an alkene to the epoxide
    Epoxide

    An epoxide is a cyclic ether with only three ring atoms. This ring approximately is an equilateral triangle which makes it highly ring strain....
     and then by saponification
    Saponification

    Saponification is the hydrolysis of an ester under base conditions to form an alcohol and the salt of a carboxylic acid . Saponification is commonly used to refer to the reaction of a metallic alkali with a fat or oil to form soap....
     to the diol for example in the synthesis of trans-cyclohexanediol batch or by microreactor
    Microreactor

    A microreactor or microstructured reactor or microchannel reactor is a device in which chemical reactions take place in a confinement with typical lateral dimensions below 1 mm;...
     :
  • A chemical reaction called Sharpless asymmetric dihydroxylation
    Sharpless asymmetric dihydroxylation

    Sharpless asymmetric dihydroxylation is the chemical reaction of an alkene with osmium tetroxide in the presence of a chirality quinine ligand to form a vicinal diol....
     can be used to produce chiral
    Chirality (chemistry)

    The term chiral is used to describe an object that is non-Superposition on its mirror image.Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands...
     diols from alkenes using an osmate reagent
    Reagent

    A reagent or reactant is a substance or compound consumed during a chemical reaction. Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants....
     and a chiral catalyst.


  • Another method is the Woodward cis-hydroxylation
    Woodward cis-hydroxylation

    The Woodward cis-hydroxylation is the chemical reaction of alkenes with iodine and silver acetate in wet acetic acid to form cis-diols. The reaction is named after its discoverer, Robert Burns Woodward....
     (cis diol) and the related Prévost reaction
    Prévost reaction

    The Pr?vost reaction is chemical reaction in which an alkene is converted by iodine and the silver salt of benzoic acid to a Vicinal diol with anti addition stereochemistry....
     (anti diol), depicted below, which both use iodine and the silver salt of a carboxylic acid.
  • In the Prins reaction
    Prins reaction

    The Prins reaction is an organic reaction consisting of an electrophilic addition of an aldehyde or ketone to an alkene or alkyne followed by capture of a nucleophile ....
     1,3-diols can be formed in a reaction between an alkene
    Alkene

    In organic chemistry, an alkene, olefin, or olefine is an Saturation chemical compound containing at least one carbon-to-carbon double bond....
     and formaldehyde
    Formaldehyde

    Formaldehyde is a chemical compound with the chemical formula H2CO. It is the simplest aldehyde. Formaldehyde exists in several forms aside from H2CO: the cyclic trimer trioxane and the polymer Polyoxymethylene....
    .

Reactions

  • A diol reacts like an alcohol
    Alcohol

    In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
    , such as esterification
    Esterification

    Esterification is the general name for a chemical reaction in which two reactants form an ester as the product . Esters are common in organic chemistry and biological materials, and often have a characteristic pleasant, fruity odor....
     and ether
    Ether

    Ether is a class of organic compounds which contain an ether functional group ? an oxygen atom connected to two alkyl or aryl groups ? of general formula R?O?R....
     formation.
  • Diols such as ethylene glycol
    Ethylene glycol

    Ethylene glycol is an alcohol with two -OH groups , a chemical compound widely used as an automobile antifreeze. In its pure form, it is an odorless, colorless, syrupy, sweet tasting, toxic liquid....
     are used as co-monomer
    Monomer

    A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
    s in polymerization
    Polymerization

    In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains....
     reactions forming polymer
    Polymer

    A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
    s including some polyester
    Polyester

    Polyester 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 ....
    s and polyurethane
    Polyurethane

    A polyurethane, commonly abbreviated PU, is any polymer consisting of a chain of organic chemistry units joined by carbamate links. Polyurethane polymers are formed by reacting a monomer containing at least two isocyanate functional groups with another monomer containing at least two alcohol groups in the presence of a catalyst....
    s. A different monomer with two identical functional groups, such as a dioyl dichloride or dioic acid is required to continue the process of polymerization through repeated esterification processes.
  • In glycol cleavage
    Glycol cleavage

    Glycol cleavage is a specific type of organic chemistry oxidation. The carbon-carbon bond in a Glycol cleavage is an important reaction in the laboratory because it is useful for determining the structures of sugars....
    , the C-C bond in a vicinal
    Vicinal (chemistry)

    In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not....
     diol is cleaved with formation of ketone or aldehyde functional groups.
  • A diol can be converted to cyclic ether with acid catalyst, this is the diol cyclization.


See also

  • Alcohol
    Alcohol

    In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
    s, chemical compounds with one hydroxyl group
  • Triol
    Triol

    A triol is a chemical compound containing three hydroxyl groups , such as glycerol....
    s, chemical compounds with three hydroxyl group
  • Polyol
    Polyol

    The name polyols refers to alcohols containing multiple hydroxyl groups. In two technological disciplines polyols have special meaning: food science and polymer chemistry....
    s, chemical compounds with multiple hydroxyl groups