GB852595A - Production of dinitrosoanilines - Google Patents

Abstract

N,C-dinitroso-N-substituted anilines, where the N-substituent is an aliphatic or cycloaliphatic hydrocarbon residue which may contain halogen substituents, are prepared by gradually reacting a C-nitroso-N-substituted aniline with nitrous acid in a cooled aqueous medium in the presence of a mineral acid present in such an amount that there is not more than 0,4 moles present per mole of C-nitrosoaniline used, at the end of the nitrosation. In the preferred form, the process comprises adding gradually a molecular proportion of an alkali metal nitrite to a cooled solution of the N-substituted aniline in alcoholic hydrogen halide, adding water to the resulting mixture, reducing, if necessary, the amount of hydrogen halide present to an amount which does not exceed that required to liberate an additional mol. of nitrous acid from an alkali metal nitrite by more than 0,4 moles per mole of aniline used and then gradually adding a second mole of alkali metal nitrite to the cooled reaction mixture. The reaction preferably takes place in methanolic hydrogen chloride using sodium nitrite and 4 mols. of acid per mol of aniline used and reducing the amount of acid prior to the second nitrosation step to about 1,3 mols by the addition of an alkali metal hydroxide, carbonate or bicarbonate. The hydrocarbon substituent on the aniline reactant preferably contains up to 6 carbon atoms and may be a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, b -chloroethyl, cyclohexyl, allyl or 2-chloroallyl group. An example is given starting from methyl aniline and the effect on the yield of the final excess of acid illustrated using methyl and ethyl aniline.