Reactions of NO ₃ with aromatic aldehydes: gas-phase kinetics and insights into the mechanism of the reaction

Rate coefficients for the reaction of NOinline-formula₃ radicals with a series of aromatic aldehydes were measured in a 7300 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 inline-formulak₁= 2.6 inline-formula± 0.3, inline-formulak₂= 8.7 inline-formula± 0.8, inline-formulak₃= 4.9 inline-formula± 0.5, inline-formulak₄= 4.9 inline-formula± 0.4, inline-formulak₅= 15.1 inline-formula± 1.3, inline-formulak₆= 12.8 inline-formula± 1.2 and inline-formulak₇= 6.2 inline-formula± 0.6, respectively, in the units of 10inline-formula⁻¹⁵ cminline-formula³ molec.inline-formula⁻¹ sinline-formula⁻¹ at 298 inline-formula± 2 K. The rate coefficient inline-formulak₁₃ for the reaction of the NOinline-formula₃ radical with deuterated benzaldehyde (benzaldehyde-dinline-formula₁) was found to be half that of inline-formulak₁. The end product of the reaction in an excess of NOinline-formula₂ was measured to be Cinline-formula₆Hinline-formula₅C(O)Oinline-formula₂NOinline-formula₂. Theoretical calculations of aldehydic bond energies and reaction pathways indicate that the NOinline-formula₃ 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.