GB728509A - Improvements in and relating to inhibitors of oxidation and of related undesirable reactions - Google Patents

Abstract

A process for the production of compounds having a structural formula <FORM:0728509/IV (b)/1> 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 <FORM:0728509/IV (b)/2> 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. The Provisional Specification refers to compounds of the above formula in which R and R1 may also be aryl radicals. The products may be used for the stabilization of organic compounds such as aldehydes, ethers, petrols, fatty oils and lubricating oils. Specification 508,129 is referred to.ALSO:Compounds having a structural formula <FORM:0728509/III/1> in which R is ether hydrogen or an alkyl group, R1 is an alkyl group and R2 is a secondary alkyl group which may contain an aryl substituent are employed in the stabilization of organic compounds liable to deterioration arising from free-radical chain reactions propagated by oxidation or polymerization, such as petrols, fatty oils and lubricating oils comprizing esters or hydrocarbons. The amine may be present in amounts of 0.0002 to 3 per cent., preferably 0.001 to 0.3 per cent. by weight. Examples show the antioxidant properties of (1) N-methyl-N1-sec. butyl-p-phenylene diamine, (2) N-dimethyl-N1-sec. butyl-p-phenylene diamine, and (3) N-dimethyl-N1-isopropyl-p-phenylene diamine when incorporated in refined cracked petrols. The preparation of amines of the above formula is described (see Group IV (b)). Other amines described are N-ethyl-N1-isopropyl-p-phenylene diamine, 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, N-dimethyl-N1-2 (4-methyl) pentyl-p-phenylene diamine, N-methyl-N1-(diphenyl methyl)-p-phenylene diamine and N-methyl-N1-(1-phenyl) ethyl-p-phenylene diamine. According to the Provisional Specification R and R1 in the above formula may also represent aryl radicals. Specification 508,129 is referred to.