Relative Rates of Some Very Rapid Gaseous Bimolecular Reactions

The present paper describes a steady-state flow apparatus which permits the measurement of relative rates of rapid gas phase bimolecular association reactions at very low pressures. Using this apparatus, the relative reactivities of the methylamines with boron trifluoride were determined over the pressure range 0.009 to 0.04 mm Hg. Within the experimental error the ratio of rate constants, kCH3NH2/k(CH3)3N, was found to be pressure independent and to have a value of 1/12. A small number of experiments was made competing monomethylamine and dimethylamine for BF3; for this system the ratio of rate constants, kCH3NH2/k(CH3)2NH had an average value of 1/5. In addition to the above, experiments were made on various phenomena such as the sorption of BF3 on various surfaces, the selectivity of a diffusion pump, and the extent of base exchange reactions, insofar as these factors pertained to the understanding of the relative rate measurements.