Deuterium isotope exchange between molecular hydrogen and cyclohexylamine

Deuterium isotope exchange between molecular hydrogen and cyclohexylamine (CHA) has been studied by using the LiCHA, NaCHA, KCHA, and CsCHA salts as catalysts in a stirred reactor over the temperature range -15 to + 15/sup 0/C. The reaction in solution is very fast (comparable to the amide/ammonia and methylamide/methylamine systems), and even at -15/sup 0/C (CHA fp -17.8/sup 0/C) rate constants independent of mass transfer could be obtained only for the Li and Na salts in the present apparatus. For these, the kinetic isotope effect (k.i.e., 1.7 to 2.0) and activation parameter (E/sub a/, 11-17 kJ.mol/sup -1/) data have been compared with literature values for base-catalyzed exchange with other protic solvents. Reasons for the observed relative catalyst reactivity LiCH much less than NaCHA < KCHA < CsCHA are considered. It has been found that, under some experimental conditions, mass transfer effects can lead to an incorrect k.i.e. value when this is derived from data for a single kinetic run D/sub 2/ ..-->.. HD ..-->.. H/sub 2/. The solubility of H/sub 2/ in CHA has been measured over the temperature range -15 to +15/sup 0/C. 50 references, 5 figures, 2 tables.