THE ELIMINATION KINETICS OF 2-BROMO-3-METHYLBUTYRIC ACID IN THE GAS-PHASE

The kinetics of 2-bromo-3-methylbutyric acid in the gas phase was studied over the temperature range of 309.3-357.0 degrees C and pressure range of 15.5-100.0 torr. This process, in seasoned static reaction vessels and in the presence of the free radical inhibitor cyclohexene, is homogeneous, unimolecular, and follows first-order rate law. The observed rate coefficients are represented by the following Arrhenius equations: log k(1)(s(-1)) = (12.72 +/- 0.25) - (181.8 +/- 2.9) kJ mol(-1)(2.303RT)(-1). The primary products are isobutyraldehyde, CO, and HBr. The polar five-membered cyclic transition state type of mechanism appears to be preferred in the dehydrohalogenation process of alpha-haloacids in the gas phase. (C) 1995 John Wiley & Sons, Inc.