Atmospheric chemistry of benzaldehyde: UV absorption spectrum and reactionkinetics and mechanisms of the C6H5C(O)O-2 radical

Flash photolysis-UV absorption and long pathlength FTIR-smog chamber studie s of several reactions involving C6H5C(O) and C6H5C(O)O-2 radicals have bee n performed. It was determined that reaction of Cl atoms with C6H5CHO proce eds via abstraction of the aldehydic hydrogen to give benzoyl radicals. The sole atmospheric fate of benzoyl radicals is addition of O-2 to give perox ybenzoyl radicals. Reaction of C6H5C(O) radicals with molecular chlorine pr oceeds with a rate constant of (5.9 +/- 0.4)x10(-11) cm(3) molecule(-1) s(- 1) at 296 K and 1-700 Torr total pressure. The UV spectrum of C6H5C(O)O-2 r adicals (245-300 nm) and the self reaction were investigated simultaneously , yielding sigma(max)=(2.0 +/- 0.1)x10(-17) cm(2) molecule(-1) at 245 nm an d k(16)=(3.1 +/- 1.4)x10(-13) exp[(1110 +/- 160) K/T] cm(3) molecule(-1) s( -1), measured from 298 to 460 K. At 338 K, C6H5C(O)O-2 radicals react with NO with a rate constant of (1.6 +/- 0.4)x10(-11) cm(3) molecule(-1) s(-1). At 296 K, C6H5C(O)O-2 radicals react with NO2 with a rate constant of (1.1 +/- 0.3)x10(-11) cm(3) molecule(-1) s(-1) to form C6H5C(O)O2NO2, which unde rgoes thermal decomposition at a rate of k(-4)=(2.1(-1.5)(+5.0))x10(16) exp [-(13600 +/- 400)K/T] s(-1) in one atmosphere of air. At 296 K in 100-700 T orr of air k[C6H5C(O)O-2+NO]/k[C6H5C(O)(2)+NO2]=1.44 +/- 0.15. Relative rat e methods were used to measure k[Cl+C6H5C(O)Cl]=(1.1 +/- 0.2)x10(-15) cm(3) molecule(-1) s(-1) at 296 K. Uncertainty limits are all two standard devia tions. Results are discussed with respect to the literature data and the at mospheric chemistry of benzaldehyde.