GB493960A - Improvements in the manufacture of hydroxy amino compounds - Google Patents

Abstract

An aromatic or heterocyclic nitro compound is converted into an aminohydroxy compound by reducing the nitro compound, in the presence of water, to the corresponding hydroxylamine derivative, and heating the latter, without isolation from the solution, with a non-oxidizing acid, whereby the hydroxyl group of the hydroxylamine residue is transferred to the nucleus; the mixture is then cooled and neutralized to recover the aminohydroxy compound. The reduction of the nitro compound may be effected with zinc dust, sodium or ammonium hydrosulphide, aluminium or hydrogen, and may be catalysed by addition of a water-soluble salt of ammonia or of an amine or of an alkaline earth metal with an acid which forms a water-soluble zinc salt; specified catalysts are ammonium chloride, sulphate and acetate, methylamine hydrochloride, and calcium chloride. In an example, an emulsion of nitrobenzene in aqueous ammonium chloride is treated with zinc dust, and afterwards filtered to remove zinc hydroxide; the filtrate, containing phenylhydroxylamine, is acidified with sulphuric acid, heated to 80-100 DEG C., cooled, and made slightly alkaline by addition of ammonia, whereby a precipitate of p-aminophenol is obtained. Other nitro compounds which may be treated are bromonitrobenzenes, nitrotoluenes, nitroxylenes, nitronaphthalenes, nitroanthracenes, nitroanthraquinones, nitropyridines, nitroquinolines and nitrothiophenes. Specification 221,227, [Class 2 (iii)], is referred to.