Some reactions of ammonia and primary amines with propanal, 2-chloroethanal, 2,2-dichloroethanal and 2,2,2-trichloroethanal in acetonitrile

Abstract

The reaction of ammonia with propanal in acetonitrile produces the hexahydrotriazine, 1, in good yield. The corresponding reaction of chloroethanal yields the cyclic trimer 16 but only in poor yield. Increasing chloro-substitution in the aldehyde stabilises the initially formed carbinolamines and disfavours trimerisation. Imines formed by reaction of primary amines with the aldehydes are relatively stable. Those formed from aliphatic amines may undergo slow dimerisation by C–C bond formation and this may be accompanied by loss of amine to yield products containing a conjugated double-bond system.Kinetic and equilibrium data are reported for both the forward and reverse reactions involving interconversion of propanal and ammonia with 1 in acetonitrile–water mixtures. The results indicate that dehydration of the carbinolamine is rate determining.