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 (pT=100–400 Torr). No pressure dependence of the rate coefficients was observed. The weighted average values obtained, kOH±2σ, in units of 10−11 cm3 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 O3. 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.