Proton magnetic resonance study of trimethylamine–trimethylborane

Abstract

Broad-line and pulsed proton magnetic resonance spectra of trimethylamine-trimethylborane have been obtained in the temperature range from approximately liquid-nitrogen temperature to 350 K. Motions of and within the molecules are deduced from a comparison of the observed second moments at various temperatures with theoretically estimated second moments. Reorientation of the methyl groups attached to boron, at frequencies sufficient to narrow the n.m.r. line, is observed at the lowest temperature attained, whereas reorientation of the methyl groups attached to nitrogen and reorientation of the whole molecule at n.m.r. line width frequencies occur simultaneously at higher temperatures. Two minima in the curve of spin-lattice relaxation time as a function of frequency can be interpreted in terms of these reorientational motions, and activation energies are calculated for the reorientation processes.