Kinetics of quaternization and conformational analysis of some substituted NN-dimethylcyclohexylamines

The rates of quaternization of a number of substituted NN-dimethylcyclohexylamines with methyl iodide in methanol have been measured at 30 and 40°C, and the conformations of these compounds are analysed from the kinetic data. The conformational free-energy difference for the dimethylamino-group is found to be –2·3 kcal mol–1 at 30°C and that for the phenyl group –3·0 kcal mol–1. The kinetic data indicate that trans-3,3,5-trimethyl- and 3,3,5,5-tetramethyl-NN-dimethylcyclohexylamine exist in the non-chair conformation.