Synthesis
Cyclohexane-1,4-diamine is one of several produced when p-phenylene diamine is hydrogenated on nickel or cobalt catalysts in methylcyclohexane or dioxane or decaline at 180° C./100 or 150 atmospheres. Trans-1,4-Diaminocyclohexane can be obtained from this isomeric mixture by fractional crystallization as described in U.S. Pat. No. 3,657,345, but several crystallizations are required to achieve this.
A process is disclosed for selectively making trans-1,4-Diaminocyclohexane by reacting ammonia with a mixture of cis and trans-cyclohexane-1,4-dicarboxylic acid, a lower alkyl ester, a glycol ester, an oligomeric ester or a polyester to make a solid trans-dicarboxylic acid diamide in a first step. The diamide is chlorinated to form trans-cyclohexane-1,4-dicarboxylic acid-bis-N-chloramide. The latter compound is then converted into a trans-1,4-Diaminocyclohexane with an alkali or alkaline earth metal hydroxide.
Purification Methods
Recrystallise the diamine from pet ether under N2 or Ar as it should be an even stronger base than the above 1,2-diamine isomers. It distils under N2. Store in the dark under N2. [Beistein 13 I 3, 13 III 11.]
