Rate Coefficients for Reaction of OH with Acetone between 202 and 395 K

Abstract

The kinetics of the title reaction were investigated between 202 and 395 K and at 20, 50, and 100 Torr of Ar or N2 bath gas using pulsed laser photolysis (PLP) generation of OH combined with both resonance fluorescence (RF) and laser-induced fluorescence (LIF) detection. OH was generated either by the sequential 439 nm, two-photon dissociation of NO2 in the presence of H2, or by HONO photolysis at 351 nm. The accuracy of the rate constants obtained was enhanced by optical absorption measurements of acetone concentrations both before and after the photolysis reactor. The temperature dependence is not described by a simple Arrhenius expression but by k1 (202-395 K) = 8.8 × 10-12 exp(-l 320/T) + 1.7 × 10-14 exp(423/T) cm3 s-1, indicating that a simple H atom abstraction may not be the only reaction mechanism. The estimated total error (95% confidence) associated with the rate coefficient derived from this expression is estimated as 5% and is independent of temperature. The curvature in the Arrhenius plot results in a significantly larger rate coefficient at low temperatures than obtained by extrapolation of the previous measurement and implies greater significance for the reaction with OH as a sink for acetone in the upper troposphere than presently assumed.