Chloroacetic acids
Encyclopedia
In organic chemistry
, the chloroacetic acids (systematic name chloroethanoic acids) are three related chlorocarbon carboxylic acid
s:
As the number of chlorine
atoms increases, the electronegativity
of that end of the molecule increases, and the molecule adopts a progressively more ionic
character: its density
, boiling point
and acidity all increase.
. Even neutral salts however, tend to be significantly toxic, because the ions interfere in biological processes (such as the citric acid cycle
) that normally process plain acetate ions. Interestingly, the chloroacetate anion is the most toxic, with a rat, oral of about 0.5 g/kg.
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
, the chloroacetic acids (systematic name chloroethanoic acids) are three related chlorocarbon carboxylic acid
Carboxylic acid
Carboxylic 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:
- Chloroacetic acidChloroacetic acidChloroacetic acid, industrially known as monochloroacetic acid is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building-block in organic synthesis.-Production:...
(chloroethanoic acid ), CH2ClCOOH - Dichloroacetic acidDichloroacetic acidDichloroacetic acid, often abbreviated DCA, is the chemical compound with formula . It is an acid, an analogue of acetic acid, in which two of the three hydrogen atoms of the methyl group have been replaced by chlorine atoms. The salts and esters of dichloroacetic acid are called dichloroacetates...
(dichloroethanoic acid), CHCl2COOH - Trichloroacetic acidTrichloroacetic acidTrichloroacetic acid is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms....
(trichloroethanoic acid), CCl3COOH
As the number of chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
atoms increases, the electronegativity
Electronegativity
Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
of that end of the molecule increases, and the molecule adopts a progressively more ionic
Ionic bond
An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed between a cation, which is usually a metal, and an anion, which is usually a nonmetal. Pure ionic bonding cannot exist: all ionic compounds have some...
character: its density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
, boiling point
Boiling point
The 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....
and acidity all increase.
| Acid | Melting point (°C) | Boiling point (°C) | Density (g/cm3) | pKa |
| Acetic acid Acetic acid Acetic 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... |
16.5 | 118.1 | 1.05 | 4.76 |
| Chloroacetic acid Chloroacetic acid Chloroacetic acid, industrially known as monochloroacetic acid is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building-block in organic synthesis.-Production:... |
61-63 | 189 | 1.58 | 2.87 |
| Dichloroacetic acid Dichloroacetic acid Dichloroacetic acid, often abbreviated DCA, is the chemical compound with formula . It is an acid, an analogue of acetic acid, in which two of the three hydrogen atoms of the methyl group have been replaced by chlorine atoms. The salts and esters of dichloroacetic acid are called dichloroacetates... |
9.5 | 194 | 1.57 | 1.25 |
| Trichloroacetic acid Trichloroacetic acid Trichloroacetic acid is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms.... |
57 | 196 | 1.63 | 0.77 |
Production
- Chloroacetic acid is mainly made by hydrolysingHydrolysisHydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
trichloroethyleneTrichloroethyleneThe chemical compound trichloroethylene is a chlorinated hydrocarbon commonly used as an industrial solvent. It is a clear non-flammable liquid with a sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, which is commonly known as chlorothene.The IUPAC name is...
in the presence of sulfuric acidSulfuric 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...
:
- CCl2= CHCl + 2 H2O → CH2ClCOOH + 2 HCl
- Dichloroacetic acid is manufactured in small quantities by reducing trichloroacetic acid.
- Trichloroacetic acid is made by directly reacting chlorine with acetic acid using a suitable catalyst.
Uses
- Chloroacetic acid is chemical intermediate for production of various pharmaceuticals and insecticideInsecticideAn insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
s. - Trichloroacetic acid is used for various analytic tests in biochemistryBiochemistryBiochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
. In sufficient concentration it will cause proteinProteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, DNADNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
and RNARNARibonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
to precipitate out of solutionSolutionIn chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
. - The sodiumSodiumSodium 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...
saltSaltIn chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
of trichloroacetic acid is used as a weedkiller.
Safety
All of these acids are unusually strong for organic acids, and should generally be treated with similar care as for strong mineral acids like hydrochloric acidHydrochloric acid
Hydrochloric 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....
. Even neutral salts however, tend to be significantly toxic, because the ions interfere in biological processes (such as the citric acid cycle
Citric acid cycle
The citric acid cycle — also known as the tricarboxylic acid cycle , the Krebs cycle, or the Szent-Györgyi-Krebs cycle — is a series of chemical reactions which is used by all aerobic living organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and...
) that normally process plain acetate ions. Interestingly, the chloroacetate anion is the most toxic, with a rat, oral of about 0.5 g/kg.