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

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 k268-363KM2MP+Cl=[(7.15 ± 1.16) × 10-12 exp((566 ± 50)/T)] cm3 molecule-1 s-1 and k268-363KM2MB+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 k298KM2MP+Cl = (4.61 ± 1.28) × 10-11 and k298KM2MB+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.