Reactions of NO3 with aromatic aldehydes: Gas-phase kinetics and insights into the mechanism of the reaction

Abstract

Rate coefficients for the reaction of NO3 radicals with a series of aromatic aldehydes were measured in a 7300g L simulation chamber at ambient temperature and pressure by relative and absolute methods. The rate coefficients for benzaldehyde (BA), ortho-tolualdehyde (O-TA), meta-tolualdehyde (M-TA), para-tolualdehyde (P-TA), 2,4-dimethyl benzaldehyde (2,4-DMBA), 2,5-dimethyl benzaldehyde (2,5-DMBA) and 3,5-dimethyl benzaldehyde (3,5-DMBA) were k1Combining double low lineg 2.6g ±g 0.3, k2Combining double low lineg 8.7g ±g 0.8, k3Combining double low lineg 4.9g ±g 0.5, k4Combining double low lineg 4.9g ±g 0.4, k5Combining double low lineg 15.1g ±g 1.3, k6Combining double low lineg 12.8g ±g 1.2 and k7Combining double low lineg 6.2g ±g 0.6, respectively, in the units of 10-15g cm3g molec.-1g s-1 at 298g ±g 2g K. The rate coefficient k13 for the reaction of the NO3 radical with deuterated benzaldehyde (benzaldehyde-d1) was found to be half that of k1. The end product of the reaction in an excess of NO2 was measured to be C6H5C(O)O2NO2. Theoretical calculations of aldehydic bond energies and reaction pathways indicate that the NO3 radical reacts primarily with aromatic aldehydes through the abstraction of an aldehydic hydrogen atom. The atmospheric implications of the measured rate coefficients are briefly discussed.