Temperature-dependence study of the gas-phase reactions of atmospheric Cl atoms with a series of aliphatic aldehydes

The reactions of Cl with a series of linear aldehydes: propanal (k1), n-butanal (k2), n-pentanal (k3), n-hexanal (k4) and n-heptanal (k5), were investigated for the first time as a function of temperature in the range 265–381 K, by laser photolysis-resonance fluorescence. The obtained kinetic data were used to derive the Arrhenius expressions: k1=(2.41±0.23) × 10−11 exp[(453 ± 54)/T], k2=(3.09 ± 0.40) × 10−11 exp[(446 ± 77)/T], k3=(4.17 ± 0.54) × 10−11 exp[(450 ± 80)/T], k4=(7.91 ± 0.66) × 10−11 exp[(349 ± 51)/T] and k5=(1.06 ± 0.20) × 10−10 exp[(306 ± 115)/T] (in units of cm3 molecule−1 s−1). To our knowledge, these are also the first absolute kinetic data reported for each of the reactions studied. The obtained rate coefficients are compared with previous studies carried out by relative techniques at room temperature, and also with the reactivity towards the OH radicals. The results are also discussed in terms of the structure–reactivity relationship. In addition, the atmospheric implications are discussed.