Rate coefficients for the reactions of OH radicals with the keto/enol tautomers of 2,4-pentanedione and 3-methyl-2,4-pentanedione, allyl alcohol and methyl vinyl ketone using the enols and methyl nitrite as photolytic sources of OH

Abstract

The kinetics of the reaction of OH radicals with 2,4-pentanedione and 3-methyl-2,4-pentanedione have been investigated in the gas-phase using a pulsed laser photolysis-laser induced fluorescence (PLP-LIF) technique. Hydroxyl radicals were generated from the parent compounds following pulsed laser photolysis at 248 nm. The rate coefficients were also determined using a conventional relative rate method. Average values of the bimolecular rate coefficients of k(OH + CH 3C(O)CH C(OH)CH 3) = (8.78 ± 0.58) × 10 −11, k(OH + CH 3C(O)C(CH 3) C(OH)CH 3) = (6.06 ± 0.54) × 10 −11 and k(OH + CH 3C(O)CH(CH 3)C(O)CH 3) = (1.16 ± 0.09) × 10 −11 cm 3 (molecule s) −1 were determined at 298 ± 2 K. Rate coefficients for the reaction of OH radicals with allyl alcohol and methyl vinyl ketone were also determined at 298 ± 2 K using the PLP-LIF technique employing the photolysis of 2,4-pentanedione and 3-methyl-2,4-pentanedione as the OH radical sources respectively, k(OH + CH 2 CHCH 2OH) = (4.60 ± 0.19) × 10 −11 and k(OH + CH 2 CHC(O)CH 3) = (1.86 ± 0.12) × 10 −11 cm 3 (molecule s) −1. The measured rate coefficients are used to derive tropospheric lifetimes for the compounds.