A PLP-LIF kinetic study of the atmospheric reactivity of a series of C4-C7 saturated and unsaturated aliphatic aldehydes with OH

Absolute rate coefficients for the reaction of OH radical with a series of saturated and unsaturated aliphatic aldehydes were measured with the pulsed laser photolysis/laser-induced fluorescence technique at room temperature and as a function of total pressure (P-T= 100-400 Torr). No pressure dependence of the rate coefficients was observed. The weighted average values obtained, k(OH) +/- 2sigma, in units of 10(-11) cm(3) molecule(-1) s(-1), were 2.88 +/- 0.26 for n-butanal, 2.48 +/- 0.24 for n-pentanal, 2.60 +/- 0.21 for n-hexanal, 2.96 +/- 0.23 for n-heptanal, 3.51 +/- 0.71 for crotonaldehyde, 2.35 +/- 0.32 for trans-2-pentenal, 2.95 +/- 0.45 for trans-2-hexenal and 2.45 +/- 0.30 for trans-2-heptenal, respectively. The results are compared with previous data when available and with the corresponding coefficients for the reactions with NO3 and O-3. The dominant tropospheric chemical loss process for these aliphatic aldehydes is the daytime reaction with OH, except in the case of trans-2-heptenal where the estimated lifetime for the reaction with NO3 radical is smaller than the corresponding value for the OH reaction. (C) 2002 Published by Elsevier Science Ltd.