Improvements in and relating to inhibitors of oxidation and of related undesirable reactions

A process for the production of compounds having a structural formula in which R is either hydrogen or an alkyl group, R1 is an alkyl group and R2 is a secondary alkyl group which may contain an aryl substituent, comprises reductively alkylating the corresponding nitroso amines having a structure by hydrogenation in the presence of the appropriate ketone under conditions which do not lead to the occurrence of a substantial amount of nuclear hydrogenation. The hydrogenation is carried out using as a hydrogenation catalyst a metal selected from copper and the metals of Group VIII of the periodic system, such as nickel, which may be in foraminate or Raney form, platinum, which may be used as powder or on an inert support and copper, which may be in foraminate form or on a support. The reductive alkylation is effected in the liquid phase, preferably using excess of the ketone as solvent. The reaction is effected at a hydrogen pressure of at least 25 atmospheres and may be carried out in two steps, for example at temperatures of 60 DEG to 100 DEG C. and 140 DEG to 200 DEG C. respectively. The process may be operated continuously. In example (1) N-methyl-N1-sec.-butyl-p-phenylene diamine is prepared by reacting N-methyl-p-nitrosoaniline with methyl ethyl ketone and hydrogen in the presence of a platinum on charcoal catalyst. Similarly prepared are (2) N-dimethyl-N1-sec.-butyl-p-phenylene diamine, and (3) N-dimethyl-N1-isopropyl-p-phenylene diamine. In example (4) a mixture of N-ethyl-N1-isopropyl-p-phenylene diamine and N-ethyl-N-isopropyl-N1-isopropyl-p-phenylene diamine is produced by reacting N-ethyl-p-nitroso aniline, acetone and hydrogen similarly. Also described are N-ethyl-N1-sec.-butyl-p-phenylene diamine, N-methyl-N1-isopropyl-p-phenylene diamine, N-diethyl-N1-sec.-butyl-p-phenylene diamine, N-methyl-N-isopropyl-N1-isopropyl-p-phenylene diamine and N-dimethyl-N1-2-(4 methyl)-pentyl-p-phenylene diamine. Such compounds are characterized variously as their mono- and di-picrolonates, hydrochlorides, picrates, and mono- and di-tosyl derivatives. From aromatic ketones can be produced, for example, N - methyl - N1 - (diphenylmethyl) - p - phenylene diamine and N-methyl-N1-(1-phenyl)-ethyl-p-phenylene diamine. As by-products in the reaction of N-methyl or ethyl-p-nitrosoaniline and acetone in the presence of hydrogen, N - methyl- and N - ethyl - N - isopropyl - N1 - iso - propyl-p-phenylene diamines are formed. Th