Kinetics of the Gas-Phase Reactions of OH Radicals, NO3 Radicals and O3 with Three C7-Carbonyls Formed From The Atmospheric Reactions of Myrcene, Ocimene and Terpinolene

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Abstract

Rate constants for the gas-phase reactions of OH radicals, NO3 radicals and O3 with the C7-carbonyl compounds 4-methylenehex-5-enal [CH2═CHC(═CH2)CH2CH2CHO], (3Z)- and (3E)-4-methylhexa-3,5-dienal [CH2═CHC(CH3)═CHCH2CHO] and 4-methylcyclohex-3-en-1-one, which are products of the atmospheric degradations of myrcene, Z- and E-ocimene and terpinolene, respectively, have been measured at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained (in cm3 molecule−1 s−1 units) were: for 4-methylenehex-5-enal, (1.55 ± 0.15) × 10−10, (4.75 ± 0.35) × 10−13 and (1.46 ± 0.12) × 10−17 for the OH radical, NO3 radical and O3 reactions, respectively; for (3Z)-4-methylhexa-3,5-dienal: (1.61 ± 0.35) × 10−10, (2.17 ± 0.30) × 10−12, and (4.13 ± 0.81) × 10−17 for the OH radical, NO3 radical and O3 reactions, respectively; for (3E)-4-methylhexa-3,5-dienal: (2.52 ± 0.65) × 10−10, (1.75 ± 0.27) × 10−12, and (5.36 ± 0.28) × 10−17 for the OH radical, NO3 radical and O3 reactions, respectively; and for 4-methylcyclohex-3-en-1-one: (1.10 ± 0.19) × 10−10, (1.81 ± 0.35) × 10−12, and (6.98 ± 0.40) × 10−17 for the OH radical, NO3 radical and O3 reactions, respectively. These carbonyl compounds are all reactive in the troposphere, with daytime reaction with the OH radical and nighttime reaction with the NO3 radical being predicted to dominate as loss processes and with estimated lifetimes of about an hour or less.

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