Secondary and tertiary aniline bases

The N-alkyl derivatives of aniline, such as N-methylaniline and N,N-dimethylani-line, are produced by the reaction of aniline at around 200 °C with an excess of the appropriate alcohol, under pressure (30 to 50 bar) in the presence of an add catalyst (H2SO4, H3PO4) they are commonly used in the production of dyestuffs. 

Production of N,N-dimethylaniline in Western Europe in 1985 was around 9,0001. Among the most important compounds based on N,N-dimethylaniline is Michler s ketone, which is used to manufacture triphenylmethane dyes such as Basic Violet 3 (Crystal Violet) or Basic Green 4 (Malachite Green), which is obtainable by reaction with benzaldehyde in a sulfuric acid medium, followed by oxidation. 

Diphenylamine is produced by the condensation of aniline in the presence of small amounts of mineral acid, with the release of ammonia. The crude diphenyl-amine/aniline mixture is refined by fractional distillation. Diphenylamine can also be produced by the reaction of chlorobenzene and aniline under pressure CU2O/ KCl is used as a catalyst. 

Diphenylamine is used as an intermediate in the production of dyes and in the form of N-nitrosodiphenylamine as a vulcanization retarder. In some countries, e.g. in West Germany, the application of this nitroso compound is banned, because of its carcinogenicity, particularly in combination with secondary amines. 

Phenothiazine is produced in 90% yield by the reaction of diphenylamine and sulfur, using iodine as a catalyst, at 180 °C. It is used as a raw material in the production of antioxidants and psychotropic drugs, such as promazine. 

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