Kinetics of the Gas-Phase Reactions of OH Radicals, NO_3 Radicals and O_3 with Three C_7-Carbonyls Formed From The Atmospheric Reactions of Myrcene, Ocimene and Terpinolene

摘要

Rate constants for the gas-phase reactions of OH radicals, NO_3 radicals and O_3 with the C_7-carbonyl compounds 4-methylenehex-5-enal [CH_2=CHC(=CH_2)CH_2CH_2CHO], (3Z)- and (3E)-4-methylhexa-3,5-dienal [CH_2=CHC(CH_3)=CHCH_2CHO] 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 cm~3 molecule~(-1) s~(-1) units) were: for 4-methylenehex-5-enal, (1.55 +- 0.15) x 10~(-10),(4.75 +- 0.35) x 10~(-13) and (1.46 +- 0.12) x 10~(-17) forme OH radical, NO_3 radical and O_3 reactions, respectively; for (3Z)-4-methylhexa-3,5-dienal: (1.61 +- 0.35) x 10~(-10), (2.17 +- 0.30) x 10~(-12), and (4.13 +- 0.81) x 10~(-17) for the OH radical, NO_3 radical and O_3 reactions, respectively; for (3E)-4-methylhexa-3,5-dienal: (2.52 +- 0.65) x 10~(-10), (1.75 +- 0.27) x 10~(-12), and (5.36 +- 0.28) x 10~(-17) for the OH radical, NO_3 radical and O_3 reactions, respectively; and for 4-methylcyclohex-3-en-1-one: (1.10 +- 0.19) x 10~(-10), (1.81 +- 0.35) x 10~(-12), and (6.98 +- 0.40) x 10~(-17) for the OH radical, NO_3 radical and O_3 reactions, respectively. These carbonyl compounds are all reactive in the troposphere, with daytime reaction with the OH radical and nighttime reaction with the NO_3 radical being predicted to dominate as loss processes and with estimated lifetimes of about an hour or less.