GB434725A - Manufacture of diazonium compounds from 4-aminodiarylamines - Google Patents

Abstract

In the diazotization of 4-aminodiarylamines, loss due to secondary reactions is reduced or avoided by effecting the diazotization in a medium having a pH value between 1 and 4. Suitable media are solutions of salts such as zinc chloride, copper chloride, copper sulphate, ferrous sulphate or aluminium sulphate of a concentration sufficient to give a pH value within the limits specified; buffer solutions, dilute acids, or solutions of mixtures of acids and salts of a pH value within the limits specified may also be used. Specified amines are substituted or unsubstituted 4-amino-diphenylamines and -naphthylphenylamines; the substituents, if present, may be alkyl or alkoxy groups or halogen atoms. The amine is preferably treated in a finely divided form; for example, it may be ground with addition of a suspending or dispersing agent, or it may be dissolved in a water-soluble solvent before addition to the reaction medium. In the examples: (1) a suspension of 4-amino-3-methoxydiphenylamine in zinc chloride solution is treated with sodium nitrite solution, and the zinc chloride double salt of the diazo compound is then salted out by addition of sodium chloride; (4<1> - aminonaphthyl - 1<1>) - 4 - ethoxyphenylamine may be diazotized similarly; (2) an alcoholic solution of 4 - amino - 3 - methyl - 6 - ethoxydiphenylamine is poured into an aqueous solution of zinc chloride and sodium nitrite, and the product is worked up as in in example 1; 4 - amino - 2 : 5 - dimethoxydiphenylamine, 4 - amino - 3 - methyl - 4<1> - methoxydiphenylamine, and 4 - aminophenyl - (6<1> - ethoxynaphthyl-2<1>)-amine may be diazotized similarly; (3) an alcoholic solution of 4-aminodiphenylamine is added to an aqueous solution of copper chloride and sodium nitrite, and the diazo compound is recovered by successive addition of zinc chloride and sodium chloride; 4-amino-2 : 5-dimethyldiphenylamine and 4-aminophenyl - 1 - (6<1> - ethoxynaphthyl - 3<1>) - amine may be diazotized similarly; (4) an acetone solution of 4-amino-3-methoxydiphenylamine is added to an aqueous solution of ferrous sulphate and sodium nitrite, and the diazo compound is recovered as in example 3; ferrous sulphate may be replaced by copper chloride, copper sulphate, or aluminium sulphate; (5) aqueous sodium nitrite is added to a suspension of 4-amino-3-chlorophenylnaphthyl-2<1>-amine in aqueous acetic acid, and the diazo compound is recovered as in example 3; (6) an aqueous suspension of 4-amino-3-methoxydiphenylamine is added to an aqueous solution containing glycine, sodium chloride, hydrochloric acid and sodium nitrite; the diazo compound is precipitated in known manner; (7) an alcoholic solution of 4-amino-2 : 5-diethoxydiphenylamine is added to an aqueous solution of citric acid, disodium phosphate, and sodium nitrite, and the diazo compound is recovered in known manner after addition of a mineral acid; (8) an aqueous suspension of 4-amino-2<1>.5-dimethyldiphenylamine is added to an aqueous solution of sodium citrate, hydrochloric acid, and sodium nitrite. Reference is made to the use of the diazo compounds in the production of ice colours of the 2 : 3-hydroxynaphthoic arylamide series. The Specification as open to inspection under Sect. 91 states that the process may be applied to 4-aminodiarylamines substituted by cycloalkoxy, aralkoxy, aryloxy, alkylcarbonyl, arylcarbonyl, alkylsulphonyl, arylsulphonyl, acylamino, substituted aminocarbonyl and aminosulphonyl, alkylamino, arylamino, alkylthio and trifluoromethyl groups. It refers also to the treatment of 4-aminobiphenylphenylamines and 4-aminoanthracylphenylamines, and includes the following examples: (1) an alcoholic solution of 4-amino-2 : 5-dimethyldiphenylamine is added to an aqueous solution of zinc chloride and sodium nitrite, and the diazo compound is salted out; 4-amino-3-chlorophenylnaphthyl-2<1>-amine may be diazotized similarly; (2) an acetone solution of 4-aminodiphenylamine is p added to an aqueous solution of zinc chloride, and the mixture is treated with aqueous sodium nitrite; the diazo compound is then salted out. This subject-matter does not appear in the Specification as accepted.