J. A. J. Den Hartog

Methylamine-deuterium isotope exchange equilibriums in the gaseous and liquid phases

The deuterium-protium separation factor, ..cap alpha.., between molecular hydrogen and liquid methylamine in the presence of potassium methylamide catalyst has been measured at low deuterium concentrations over the temperature range -50 to 5/sup 0/C. The separation factor is about 10% larger than that for liquid ammonia, and its dependence upon absolute temperature, T, is given by ln ..cap alpha.. = 0.1135 + (240.05/T) + (43,989/T/sup 2/). The equilibrium constant, K/sub 1/, for deuterium-protium exchange between hydrogen and the amino group of methylamine vapor has been calculated for all deuterium concentration at temperatures between 150 and 400 K with partition functions for methylamine derived from an internal rotation-inversion-normal vibration model of methylamine based on spectroscopic data. Conversion of K/sub 1/ into ..cap alpha.. values, by inclusion of vapor-liquid fractionation effects, shows that the discrepancy between theory and experiment is less than the combined tolerances (+- 5%) of the two approaches. The dependence of ..cap alpha.. on deuterium atom fraction is discussed.