GB719881A - Process for the production of substituted carboxylic acids - Google Patents

Abstract

Substituted aromatic carboxylic acids or ammonium salts thereof are made by reacting at elevated temperature and pressure, an aromatic compound containing a -CH2Cl or -CHCl2 group and a neutralized sulphonic acid group, with an aqueous solution of an ammonium polysulphide or with sulphur and an aqueous solution of ammonia. Thus the ammonium salt of benzoic acid-p-sodium sulphonate may be obtained from p-toluene-sodium sulphonate after chlorination, the benzyl chloride- and benzal chloride-p-sodium sulphonates being converted as above and the benzotrichloride - p - sodium sulphonate being hydrolysed during the reaction. Residual p-toluene-sodium sulphonate from the chlorination step remains unchanged. Preferably 1.3-1.5 gram atoms of chlorine are introduced per mol. of starting material. o-Toluene-sodium sulphonate may also be treated. The sulphonic acid group is preferably neutralized by an ammonium radicle or an alkali metal. In examples: (1) p-toluene-sodium sulphonate is chlorinated whilst irradiated and the product treated with sulphur and aqueous ammonia in an autoclave at 180 DEG C. to yield the ammonium salt of benzoic acid-p-sodium sulphonate; and (2) chlorinated o-toluene-sodium sulphonate is treated as in the latter part of (1) to yield the ammonium salt of benzoic acid-o-sodium sulphonate. In both examples the corresponding free acids may be obtained on acidification.