GB629534A - Improved process for the preparation of aliphatic amino-polymethylene-carboxylicacid-amides - Google Patents

Abstract

Aliphatic amino-polymethylene-carboxylic acid amides having more than 5 carbon atoms and in which the amide and amine groups are in terminal position, are prepared by heating, optionally in an ammonia stream, a normal dicarboxylic acid diamide having more than 5 carbon atoms, and either or not in the presence of a dehydration catalyst, until 52.5 to 57.5 per cent by weight of the quantity of water which would be split off theoretically to form the di-nitrile, has been given off, and then submitting the formed mononitrile-carboxylic acid amide to catalytic hydrogenation under pressure. Alternatively, a normal polymethylene dicarboxylic acid having more than 5 carbon atoms is heated in an ammonia stream or with other substances giving off ammonia, e.g. ammonium carbonate or urea, to form, first of all, the dicarboxylic acid diamide and the heating continued until 76.25 per cent to 78.75 per cent by weight of the total quantity of water, which would be liberated theoretically in forming the dinitrile from the dicarboxylic acid via the diamide, has been given off (the stated percentages are based on the assumption that the diamide is formed as an intermediate from the dicarboxylic acid in 100 per cent theoretical yield), the mono-nitrile carboxylic acid amide being thus formed in one operation, and then subjecting the latter to catalytic hydrogenation under pressure. Specified dehydration catalysts which may be used are silica gel, boron phosphate and aluminium oxide and as hydrogenating catalysts those of the iron group, particularly nickel and cobalt may be used. The hydrogenating catalyst may be precipitated on carriers such as infusorial earth or aluminium oxide or may be used in the form of Raney-catalysts, e.g. those formed by alloying nickel with aluminium and dissolving the aluminium from the resultant alloy. The hydrogenation is preferably effected in the presence of ammonia and at between 80 DEG and 135 DEG C. under a hydrogen pressure of 40 to 300 atmospheres and inert solvents such as aliphatic alcohols or dioxane may be present. The amino carboxylic acid amides obtained in the process may be hydrolysed to form the free amino acid. In an example, adipic acid diamide is heated with boron phosphate in an ammonia stream at 280-325 DEG C. until 55 per cent by weight of the quantity of water which would be split off theoretically to form the di-nitrile, has been given off. The residue is fractionally distilled, yielding the mononitrile carboxylic acid amide together with some adipic acid dinitrile and cyclopentanone. The mononitrile carboxylic acid amide together with some adipic acid dinitrile and cyclopentanone. The mononitrile carboxylic amide is then mixed with a catalyst made by reducing cobalt carbonate precipitated on infusorial earth, and reduced with hydrogen at 125 DEG C. and under a pressure of 130 atmospheres, in the presence of ammonia and dioxane. The mixture is cooled, filtered and fractionated to yield 6-amino capronic acid amide. Specification 282,083, [Class 2 (iii)], and U.S.A. Specification 1,628,190 are referred to. The Specification as open to inspection under Sect. 91 states that the diamide starting material may be heated until half the quantity of water which would be split off theoretically to form the dinitrile, has been given off. This subject-matter does not appear in the Specification as accepted.