Rate constants for the gas‐phase reaction of OH radicals with a series of ketones at 299 ± 2 K

Relative rate constants for the reaction of OH radicals with a series of ketones have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of hydroxyl radicals. Using a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10 −12 cm 3 molecule −1 s −1 , the rate constants obtained are (× 10 12 cm 3 molecule −1 s −1 ): 2‐pentanone, 4.74 ± 0.14; 3‐pentanone, 1.85 ± 0.34; 2‐hexanone, 9.16 ± 0.61; 3‐hexanone, 6.96 ± 0.29; 2,4‐dimethyl‐3‐pentanone, 5.43 ± 0.41; 4‐methyl‐2‐pentanone, 14.5 ± 0.7; and 2,6‐dimethyl‐4‐heptanone, 27.7 ± 1.5. These rate constants indicate that while the carbonyl group decreases the reactivity of CH bonds in the α position toward reaction with the OH radical, it enhances the reactivity in the β position.