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The acids monochloroacetic acid (CH2ClCOOH), dichloroacetic acid (CHCl2COOH), and tri-chloroacetic acid (CCl3COOH) are classed as chloroacetic acids. Monochloroacetic acid (also called simply chloroacetic acid) and trichloroacetic acid are obtained as colorless crystals, with a melting point of 61.2° and 59.2°C, respectively, and a boiling point of 189.3° and 197.6°C, respectively. Dichloroacetic acid is a colorless liquid, with a boiling point of 194.5°C. All three are soluble in water, alcohol, acetone, and ether.
Monochloroacetic acid, which is an intermediate in the production of indigo and many other vat dyes, is the most important of the three acids. It is also used in the production of carboxyl-methyl cellulose, the hypnotic barbital, vitamin B6, and various herbicides, such as the salts and esters of 2,4-dichloro-phenoxyacetic acid. It is produced by the chlorination of ice-cold acetic acid and by other methods.
Dichloroacetic acid, CHCl2COCl, which is synthesized by the oxidation of trichloroethylene, CCl2=CHCl, is also of practical importance. It is used in the synthesis of the antibiotic Levomycetin.
The main method of the production of trichloroacetic acid is the oxidation of chloral by nitric acid. The salts of trichloroacetic acid are used as herbicides, while trichloroacetic acid itself is used in biochemistry as a solvent and precipitating agent and in medicine as a cauterizing agent.