A PLP–LIF kinetic study of the atmospheric reactivity of a series of C 4–C 7 saturated and unsaturated aliphatic aldehydes with OH

Abstract

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±2 σ, 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 NO 3 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 NO 3 radical is smaller than the corresponding value for the OH reaction.