Atmospheric chemistry of benzaldehyde: UV absorption spectrum and reaction kinetics and mechanisms of the C_6H_5C(O)O_2 radical

摘要

Flash photolysis-UV absorption and long pathlength FTIR-smog chamber studies of several reactions involving C_6H_5C(O) and C_6H_5C(O)O_2 radicals have been performed. If was determined that reaction of Cl atoms with C_6H_5CHO proceeds via abstraction of the aldehydic hydrogen to give benzoyl radicals. The sole atmospheric fate of benzoyl radicals is addition of O_2 to give peroxybenzoyl radicals. Reaction of C_6H_5C(O) radicals with molecular chlorine proceeds with a rate constant of (5.9 +- 0.4) * 10~(-11) cm~3 molecule~(-1) s~(-1) at 296 K and 1-700 Torr total pressure. The UV spectrum of C_6H_5C(O)O_2 radicals (245-300 nm) and the self reaction were investigated simultaneously, yielding #sigma#_(max) = (2.0 +- 0.1) * 10~(-17) cm~2 molecule~(-1) at 245 nm and k_(16) = (3.1 +- 1.4) * 10~(13) exp[(1110 +- 160) K/T] cm~3 molecule~(-1) s~(-1), measured from 298 to 460 K. At 338 K, C_6H_5(O)O_2 radical react with NO with a rate constant of (1.6 +- 0.4) * 10~(-11) cm~3 molecule~(-1) s~(-1). At 296 K, C_6H_5C(O)O_2 radicals react with NO_2 with a rate constant of (1.6 +- 0.4) * 10~(-11) cm~3 molecule~(-1) s~(-1) to form C_6H_5C(O)O_2NO_2, which undergoes thermal decomposition at a rate of k_(-4) = (2.1_(-1.5)~(+5.0) * 10~(16) exp[-(13 600 +- 400)K/T] s~(-1) in one atmosphere of air. At 296 K in 100-700 Torr of air k[C_6H_5C(O)O_2 + NO]/k[C_6H_5C(O)_2 + NO_2] = 1.44 +- 0.15. Relative are methods were used to measure k[Cl + C_6H_5C(O)Cl] = (1.1 +- 0.2) * 10~(-15) cm~3 molecule~(-1) s~(-1) at 296 K. Uncertainty limits are all two standard deviations. Results are discussed with respect to the literature data and the atmospheric chemistry of benzaldehyde.