organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, ...

, the chloroacetic acids (systematic name chloroethanoic acids) are three related chlorocarbon carboxylic acids: *

Chloroacetic acid Chloroacetic acid, industrially known as monochloroacetic acid (MCA), is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building block in organic synthesis. It is a colorless solid. Related compounds a ...

(chloroethanoic acid), CH₂ClCOOH *

Dichloroacetic acid Dichloroacetic acid (DCA), sometimes called bichloroacetic acid (BCA), is the chemical compound with formula . It is an acid, an analogue of acetic acid, in which 2 of the 3 hydrogen atoms of the methyl group have been replaced by chlorine atoms. ...

(dichloroethanoic acid; bichloroacetic acid, BCA), CHCl₂COOH *

Trichloroacetic acid Trichloroacetic acid (TCA; TCAA; also known as trichloroethanoic acid) is an analogue of acetic acid in which the three hydrogen atoms of the methyl group have all been replaced by chlorine atoms. Salts and esters of trichloroacetic acid are calle ...

(trichloroethanoic acid), CCl₃COOH

Properties

As the number of

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

atoms increases, the

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

of that end of the molecule increases, and the molecule adopts a progressively more ionic character: its

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

, boiling point and acidity all increase. :

Production

* Chloroacetic acid is mainly made by hydrolysing

trichloroethylene The chemical compound trichloroethylene is a halocarbon commonly used as an industrial solvent. It is a clear, colourless non-flammable liquid with a chloroform-like sweet smell. It should not be confused with the similar 1,1,1-trichloroethane, w ...

in the presence of sulfuric acid: *: 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 Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

Uses

* Chloroacetic acid is chemical intermediate for production of various pharmaceuticals and insecticides. * Trichloroacetic acid is used for various analytic tests in

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

. In sufficient concentration it will cause

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

, DNA and

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

out of

solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...

. * The

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

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 acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

. Even neutral salts however, tend to be significantly toxic, because the ions interfere in biological processes (such as the

citric acid cycle The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and protein ...

) that normally process plain acetate ions. The chloroacetate

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

is the most toxic, with a rat, oral of about 0.5 g/kg.

References

{{Reflist Carboxylic acids Organochlorides