GB617448A - Improvements in methods of making aryloxymonocarboxylic acids - Google Patents

Abstract

In the manufacture of aryloxymonocarboxylic acids which may be substituted with halogen, alkyl, alkoxy, aryl, amino or nitro groups, the impure reaction product consisting of acid and phenol is melted and run in a thin stream into a selective solvent for the phenol, the pure acid being precipitated. The selective solvent should be a very good solvent for the phenol, a poor solvent for the aryloxy acid and alkali, capable of readily giving up dissolved phenol and substantially insoluble in water. As examples of solvents petroleum distillates such as kerosene, gasoline, and Diesel oil are mentioned. In an example an alkaline solution of 2 : 4-dichlorophenol is heated to dryness with monochloracetic acid and the product acidified with aqueous hydrochloric acid and boiled. Crude molten 2-4-dichlorophenoxy acetic acid which settles at the bottom of the vessel is run off into kerosene and the precipitated acid separated. The kerosene phenol solution is treated with aqueous sodium hydroxide and the phenol and kerosene recovered. In a similar way the substituted or unsubstituted aryloxymonocarboxylic aliphatic acids (e.g. acetic acid) made by reacting chlorinated aliphatic acids with o- or p-chlorophenol, 2,4,5 or 2,4,6-trichloro-phenol, 2-chloro-5-hydroxy-toluene, 2,4-, 3,4-and 3,5 - dimethyl - phenol, 2 - chloro - 4 - methyl phenol, 2-chloro-4-phenyl phenol, p-chloro-thymol and a or b -naphthol may be purified.