Kinetic Studies on the Photo-oxidation Reactions of Methyl-2-methyl Butanoate and Methyl-3-methyl Butanoate with OH Radicals

Abstract

Kinetics for the reactions of methyl-2-methyl butanoate (M2MB) and methyl-3-methyl butanoate (M3MB) with OH radicals were carried out using the relative rate technique with gas chromatography-flame ionization detection (RR-GC-FID) in the temperature range of 268-363 K and at 760 Torr of N2. The temperature-dependent rate coefficients (k in cm3 molecule-1 s-1) for the reaction of M2MB with OH radicals from 268 to 363 K were measured to be k268KM2MB+OH = (4.62 ± 1.50) × 10-12, k283KM2MB+OH = (4.46 ± 1.41) × 10-12, k298KM2MB+OH = (4.27 ± 1.20) × 10-12, k313KM2MB+OH = (3.99 ± 1.06) × 10-12, k343KM2MB+OH = (3.65 ± 0.94) × 10-12, and k363KM2MB+OH = (3.53 ± 0.80) × 10-12, respectively. Similarly, the temperature-dependent kinetics for the reaction of M3MB with OH radicals were measured to be k268KM3MB+OH = (4.49 ± 1.46) × 10-12, k283KM3MB+OH = (4.40 ± 1.36) × 10-12 , k298KM3MB+OH = (4.14 ± 1.18) × 10-12 , k313KM3MB+OH = (3.90 ± 1.06) × 10-12 , k343KM3MB+OH = (3.52 ± 0.85) × 10-12, and k363KM3MB+OH = (3.42 ± 0.81) × 10-12 respectively. Furthermore, computational calculations were carried out for the title reactions using the CVT/SCT/ISPE method. In addition to this, the product analyses for the studied reactions were elucidated using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR) as analytical tools. Based on the identified products, the possible degradation mechanisms were proposed. Atmospheric lifetimes, radiative forcings (RFs), global warming potentials (GWPs), and photochemical ozone creation potentials (POCPs) were also estimated.