Isotopic exchange reactions of amines. Part 1. An 2H nuclear magnetic resonance study of the amino to methyl group deuteron exchange in methylamine

Deuteron exchange kinetics between the methyl and amino groups in methylamine, catalyzed by potassium methylamide (PMA), have been studied by 2 H nmr. Typical values of k obs , the observed pseudo first-order exchange rate, are 1.0 × 10 −5 s −1 at 0.21 M PMA and 323 K. Effects of added potassium methylamide and temperature are described. The rate is unaffected by the thermal decomposition product of PMA and there is little or no catalysis by an equilibrium mixture of the solvated electron species e − , (e − K + ), and K − . The active catalyst in solution is shown to be monomeric PMA in equilibrium with relatively inactive dimers, ..., n-mers. A mechanism that describes the exchange and relates it to the thermal decomposition of the amide is discussed.