Conformational kinetics of methyl nitrite. III. Collisional energy transfer in the bimolecular region

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Abstract
Bimolecular region unimolecular rate constants for the syn=anti conformed exchange in gaseous methyl nitrite and in methyl nitrite–bath gas (bath gases being He, Ne, Ar, H2, N2, O2, CO, CO2, NH3, SF6, CH4, C2H6, C3H8, n-C4H10, and n-C5H12) were obtained from line shape analysis of 200 MHz 1H NMR spectra. The pressure dependent rate constants were analyzed to yield relative bimolecular collisional activation efficiencies βMp on a pressure per pressure basis for each bath gas. The resulting βMp indicate that, for methyl nitrite conformational interconversion, which occurs at a low threshold energy, E0=11.70 (0.40) kcal/mol, and a low vibrational state density ρ(E0)=160 states/cm−1 intermolecular collisional energy transfer is dominated by the attractive portion of the intermolecular potential, with the energy transfer in the collisional complex being statistical. Corrections to previously published data are given.