Rapid Gas-Phase Reactions. Amines and Boron Trifluoride. II. Pressure Dependence of Rate Constant

Relative rate constants for reaction of monomethylamine and trimethylamine with boron trifluoride are reported for the pressure range 0.04-600 Torr. The limiting ratio at low pressure is about 0.836, and the extrapolated high-pressure ratio is of the order 4. The half-pressure for quasi-bimolecular behavior of the monomethylamine-boron trifluoride system is in the vicinity of 70 Torr. When the data are combined with those of Kistiakowsky, et al., individual pressure-dependent rate constants can be estimated. The amine-BF_3 series has loose activated complexes and low energy for redistribution among internal modes, making it an unusual candidate for theoretical unimolecular study.