GB663294A - Process for the preparation of diamines - Google Patents

Abstract

Aliphatic diamines are made by reacting an aliphatic dialdehyde containing at least six carbon atoms in which the formyl groups are separated by at least four carbon atoms with ammonia or a primary or secondary amine in the presence of hydrogen and a hydrogenation catalyst under hydrogenating conditions, the aminating agent being present throughout the reaction in a molar amount at least ten times that of the aldehyde present. The diamine has the same carbon skeleton as the aldehyde from which it is made. Many dialdehydes are specified representative being adipaldehyde, azela-aldehyde and alphamethyl-delta-isopropyl-adipaldehyde. Preferred aldehydes contain six to twelve carbon atoms and the process is of particular value when using aldehydes whose formyl groups are separated by four carbon atoms, e.g. adipaldehyde, and to alkyl or hydroxyl substitution products thereof. Particular reference is made to the use of hydroxylated aldehydes when excessive reaction does not occur at the hydroxyl group and aldehydes with hydroxyl groups in the alpha position to a formyl group are especially mentioned. Many aminating agents are specified including members of the classes of primary alkyl-amines containing from one to twenty-two carbon atoms, primary or sec.-amines isomeric therewith, diamines, alkanolamines, cycloaliphatic amines, arylamines, aralkylamines, heterocyclic nitrogen bases, aminated heterocyclic compounds, amines containing olefinic or acetylenic bonds, and aminoesters, representative compounds being methyl-, myristyl-, N-butylpentyl-, cyclohexyl-, phenyl- and benzyl-amine, N-ethylaniline, trimethylenediamine, piperidine, butanolamine, ethylaminoacetate, allyl- and propargyl-amine. Amines containing saturated and/or aromatic carbon to carbon bonds are preferred. Conventional metal hydrogenation catalysts may be used, base metals being preferred, especially when in a finely-divided pyrophoric form. Raney nickel is particularly suitable. Catalyst p supports may be used. Amounts of catalyst specified range from about 1 to 20 per cent. To avoid side reactions the aminating agent is introduced into a reaction zone containing the catalyst, hydrogen added to give pressures of about 200 to 5000, preferably 500-2000, p.s.i., and the di-aldehyde added so that a substantial accumulation of unreacted dialdehyde is precluded. Aldehyde may be added in a solvent, e.g. water, lower alcohol or glycol. Gaseous amines are preferably liquefied with pressure although they may be dissolved in a solvent such as water or an alcohol. Temperatures specified being about 30-150 DEG C., preferably about 50-125 DEG C. When ammonia is used it is preferred that a twentyfold molar excess be present, e.g. about 20-70 mols. of ammonia may be used. Reaction times of 0.5-5 hours generally suffice. 2-Hydroxy-1,6-hexane diamine and N-substitution derivatives thereof are of particular importance in resin manufacture and a list of these compounds is given representative being N,N1 - diethyl-, N,N1 - diisopropyl-, N,N1 - dibenzyl-, N,N1 - dinaphthyl-, N,N1 - diphenethyl-, N,N1-dicyclopentyl-, N,N,N1,N1-tetraoctyl-, N,N1 - diphenyl - N,N1 - dimethyl-, N,N1 - dibenzyl - N,N1 - dipropyl - 2 - hydroxy - 1,6-hexane-diamine. Salts of the amines may be formed in the usual manner. In examples, alpha-hydroxyadipaldehyde is reacted in (1), (2) and (3) in aqueous solution with ammonia and hydrogen in the presence of Raney nickel to yield 2-hydroxy-1,6-hexanediamine, the adipic acid salt of which is prepared in (1), and in (4) in a similar fashion with isopropylamine and hydrogen to yield N,N1-diisopropyl-2-hydroxy-1,6 - hexanediamine. The alpha - hydroxyadipaldehydes are made by hydrolysing 3-dihydro-1,4-pyran-2-carboxaldehyde and alkyl substitution products thereof.