Kinetic Studies of OH Reactions with a Series of Ketones

Absolute rate constants have been measured for the gas-phase reactions of hydroxyl radicals with a series of ketones: acetone ( k 1 ), 2-butanone ( k 2 ), 3-methyl 2-butanone ( k 3 ), 4-methyl 2-pentanone ( k 4 ), and 5-methyl 2-hexanone ( k 5 ). Experiments were carried out using the pulsed laser photolysis−laser-induced fluorescence technique over the temperature range 243−372 K. The obtained kinetic data were used to derive the Arrhenius expressions: k 1 = (1.25 ± 0.22) × 10 -12 exp[−(561 ± 57)/ T ]; k 2 = (1.19 ± 0.18) × 10 -12 exp[−(60 ± 61)/ T ]; k 3 = (1.58 ± 0.35) × 10 -12 exp[(193 ± 65)/ T ]; k 4 = (0.759 ± 0.126) × 10 -12 exp[(834 ± 46)/ T ], and k 5 = (1.33 ± 0.63) × 10 -12 exp[(649 ± 140)/ T ] (in units of cm 3 molecule -1 s -1 ). At room temperature, the rate constants obtained (in units of 10 -12 cm 3 molecule -1 s -1 ) were as follows: acetone (0.184 ± 0.024); 2-butanone (1.19 ± 0.18); 3-methyl 2-butanone (2.87 ± 0.29); 4-methyl 2-pentanone (12.1 ± 0.9); and 5-methyl 2-hexanone (10.3 ± 1.0). Our results are compared with the previous determinations and discussed in terms of structure−reactivity relationships.