GB642597A - Improvements in or relating to the production of sulphenamides - Google Patents

Abstract

Sulphenamides are prepared from a water-soluble alkali metal salt of an organic mercaptan and an amine stronger than ammonia, containing at least one free hydrogen atom, by oxidation in aqueous solution with a hypochlorite at a constant pH. For instance, an aqueous solution of an alkali metal salt of a mercaptobenzothiazole and a primary, secondary, or cyclic amine with a dissociation constant greater than 1.8 X 10-5 is oxidized with an alkali metal hypochlorite whilst maintaining a pH corresponding to 680-710 millivolts as measured by the system antimony-saturated calomel. Of the many suitable amines specified, the following are representative: benzylamine, methylamine, propylamine, allylamine, diethylamine, morpholine, methylethylamine, methylnaphthylamine, and diphenylguanidine. Specified mercaptans include thiophenol, thio-b -naphthol, 2-mercaptothiazoline, 2-mercapto-4 : 5 - dihydroglyoxaline, 2 - mercaptobenzimidazole, 2-mercaptobenzoxazole, and 2-mercapto - 4 - ethylthiazole. 2 - Mercaptoaryl thiazoles are preferred, e.g. 2-mercaptobenzothiazole, 2-mercaptonaphthothiazole, 2-mercapto - 4 - phenylbenzothiazole, 2 - mercaptomethylbenzothiazole, and 2-mercaptochlorobenzothiazole. The pH of the oxidation, which is conveniently indicated and controlled by a potentiometer method, is of the order of 11.6 in a typical experiment. The actual value is not critical and the oxidizing potential may vary, e.g. between p 460 and 700 millivolts. The concentration of the hypochlorite solution should be at least 7.5 per cent by weight of active hypochlorite, e.g. 8-10 per cent, whilst the quantity of hypochlorite should be about 50 per cent in excess of theory. Stoichiometric amounts of mercaptan with most secondary and some primary amines are used, although 1.1 mols. of amine is preferred; in other cases a larger excess of amine, e.g. 3 mols., is desirable. The preferred temperature range is 10-30 DEG C., and particularly 20-30 DEG C., i.e. room temperature; cooling may be necessary. In the examples, and aqueous solution of sodium mercaptobenzothiazole is oxidized at constant pH with sodium hypochlorite in the presence of (1) cyclohexylamine to give cyclohexylaminothiobenzothiazole; and similarly in the presence of (2) and (3) n-butylamine; (4) n - amylamine; (5) o - cyclohexyl - cyclohexylamine; (6) monoethanolamine; (7) sec.-butylamine; (8) piperidine; and (9) ethylenediamine, to give the corresponding aminothiobenzothiazoles.