Temperature-Dependent Kinetics of the Reactions of Methyl-2-methyl Propionate and Methyl-2-methyl Butanoate with Cl Atoms under Tropospheric Conditions

Abstract

The relative rate technique coupled with gas chromatography (GC)–flame ionization detection was used to investigate the kinetics of the reaction of methyl-2-methyl propionate (M2MP) and methyl-2-methyl butanoate (M2MB) with the Cl atom between 268 and 363 K and at 760 Torr of N2 as a diluent gas. Temperature-dependent Arrhenius expressions were obtained as k 268–363K M2MP+Cl = [(7.15 ± 1.16) × 10–12 exp((566 ± 50)/T)] cm3 molecule–1 s–1 and k 268–363K M2MB+Cl = [(6.88 ± 0.80) × 10–12 exp((794 ± 125)/T)] cm3 molecule–1 s–1. The rate coefficients (in units of cm3 molecule–1 s–1) at 298 K were measured to be k 298K M2MP+Cl = (4.61 ± 1.28) × 10–11 and k 298K M2MB+Cl = (9.44 ± 1.90) × 10–11. In addition to this, the measured kinetics were also compared with the kinetics computed using the canonical variational transition state theory/small curvature tunneling /interpolated single-point energies method. The degradation mechanism was also postulated using GC–mass spectrometry and GC–infrared spectrometry as the analytical methods. Furthermore, the atmospheric lifetimes of the test molecules were estimated and are presented in this article.