CATALYTIC DEHYDRATION OF ALCOHOLS BY OH - 2-PROPANOL - AN INTERMEDIATE CASE

We describe a laser photolysis/cw, laser-induced fluorescence kinetic study of the reaction between OH and 2-propanol, measured over the temperature range 293-745 K. The rate coefficient for hydrogen atom abstraction by OH from 2-propanol is best fit by the expression k(7) = 1.044 X 10(-17) T1.86 exp(736/T) cm3 molecule-1 s-1. Chain-catalytic dehydration of 2-propanol by OH is an important component of the reaction mechanism. By using isotopic substitution, we determine, as a function of temperature, the branching ratio for H atom abstraction by OH from the beta-sites of 2-propanol. Between 500 and 600 K, biexponential [OH] decays result from the unimolecular decomposition of the H2CCH(OH)CH3 intermediate. We characterize the dissociation kinetics of this HO-propene intermediate by fitting biexponential [OH] decays to a reaction model. From these results and previously established kinetic and thermodynamic data, we estimate the strength of a methyl C-H bond in 2-propanol. Measurements above T = 600 K demonstrate a role for two minor reaction channels.