Gas-Phase Reaction Kinetic Study of a Series of Methyl-Butenols with Ozone under Atmospherically Relevant Conditions.

Abstract

Methyl-butenols are a category of oxygenated biogenic volatile organic compounds emitted by plants as part of their natural metabolic processes. This study examines the gas-phase reactions of ozone (O3) with five methyl-butenols (2-methyl-3-buten-2-ol, 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, 2-methyl-3-buten-1-ol, and 3-methyl-3-buten-2-ol) under atmospheric conditions at a temperature of (298 ± 2) K and pressure of (1000 ± 10) mbar. The experimental values for the gas-phase reaction rate coefficients obtained in this study, by using the relative rate method, are as follows (in cm3 molecule-1 s-1): k(3-methyl-2-buten-1-ol + O3) = (311 ± 20) × 10-18, k(2-methyl-3-buten-2-ol + O3) = (9.55 ± 1.04) × 10-18, k(3-methyl-3-buten-1-ol + O3) = (7.29 ± 0.46) × 10-18, k(2-methyl-3-buten-1-ol + O3) = (4.25 ± 0.29) × 10-18, and k(3-methyl-3-buten-2-ol + O3) = (62.9 ± 6.8) × 10-18. The results are discussed in detail, with particular emphasis on the degree and type of substitutions of the double bond. The determined rate coefficient values are also compared to the available literature data and with estimates of the structure-activity relationship. Additionally, the atmospheric implications toward the tropospheric lifetime and photochemical ozone generation potential for the investigated compounds are provided, which highlight the atmospheric impact of methyl-butenol decomposition into the lower atmosphere.