Process for preparing salts of quaternary ammonium monoazo dyes

摘要

The invention comprises hydrazines of formula: in which the hydrazine group is attached to a 2- or 4-carbon atom of the pyridine ring, B is a benzene radical, Y is nitro and n is 1 or 2. They are used in the preparation of azo dyes (see Group IV(c)) and are prepared by reacting a mono- or di-nitrophenylhydrazine with a 2- or 4-halo-pyridine. Compounds specified are N1-4-nitrophenyl-N2-2- or -4-pyridyl-hydrazine and N1-2:4-dinitrophenyl-N2-2-or -4-pyridyl-hydrazine. In Examples: (1) 4-nitrophenyl-hydrazine is heated in an excess of 2-bromopyridine to give 2-p-nitrophenyl-hydrazinyl-pyridine hydrobromide; (2) the product of (1) is converted to the base by heating with aqueous sodium bicarbonate. Specification 793,587 is referred to.ALSO:Azo dyes of formula:- wherein A is the residue of a pyridine nucleus having the azo group in the 2- and 4-positions to the quaternized nitrogen, R is an organic radical, B is a benzene or naphthalene radical and X- is an anion are prepared by reacting a corresponding nitroarylhydrazine with a halopyridine (see Group IV(b)), oxidizing the resulting disubstituted hydrazine to an azo compound, reducing the nitro group to amino and quaternizing said azo compound. The dyes give red shades on polyacrylonitrile fibres. In examples 2- p-nitrophenylhydrazinylpyridine hydrobromide is prepared and oxidized to the azo compound by refluxing with sodium nitrite in glacial acetic acid or by passing air into a heated mixture thereof with aqueous sodium hydroxide. The nitro-azo compound is reduced with sodium sulphide to give the amino-azo compound which is quaternized with methyl iodide. The use of 4-halopyridines and 2 : 4-dinitrophenylhydrazines as starting materials and of dimethyl sulphate, benzyl chloride and ethyl bromide as quaternizing agents is specified. Specification 793,587 is referred to.