Rate coefficients for the OH + acetaldehyde (CH3CHO) reaction between 204 and 373 K

The rate coefficient, k1, for the gas-phase reaction OH + CH3CHO (acetaldehyde) products, was measured over the temperature range 204–373 K using pulsed laser photolytic production of OH coupled with its detection via laser-induced fluorescence. The CH3CHO concentration was measured using Fourier transform infrared spectroscopy, UV absorption at 184.9 nm and gas flow rates. The room temperature rate coefficient and Arrhenius expression obtained are k1(296 K) = (1.52 ± 0.15) × 10−11 cm3 molecule−1 s−1 and k1(T) = (5.32 ± 0.55) × 10−12 exp[(315 ± 40)/T] cm3 molecule−1 s−1. The rate coefficient for the reaction OH (ν = 1) + CH3CHO, k7(T) (where k7 is the rate coefficient for the overall removal of OH (ν = 1)), was determined over the temperature range 204–296 K and is given by k7(T) = (3.5 ± 1.4) × 10−12 exp[(500 ± 90)/T], where k7(296 K) = (1.9 ± 0.6) × 10−11 cm3 molecule−1 s−1. The quoted uncertainties are 2σ (95% confidence level). The preexponential term and the room temperature rate coefficient include estimated systematic errors. k7 is slightly larger than k1 over the range of temperatures included in this study. The results from this study were found to be in good agreement with previously reported values of k1(T) for temperatures <298 K. An expression for k1(T), suitable for use in atmospheric models, in the NASA/JPL and IUPAC format, was determined by combining the present results with previously reported values and was found to be k1(298 K) = 1.5 × 10−11 cm3 molecule−1 s−1, f(298 K) = 1.1, E/R = 340 K, and Δ E/R (or g) = 20 K over the temperature range relevant to the atmosphere. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 635–646, 2008