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 CI atom between 268 and 363 K and at 760 Torr of N-2 as a diluent gas. Temperature-dependent Arrhenius expressions were obtained as k(268-363K)(M2MP+Cl) = [(7.15 +/- 1.16) X 10(-12) exp((566 +/- 50)/T)] cm(3) molecule(-1) s(-1) and k(268-363K)(M2MB+Cl) = [(6.88 +/- 0.80) X 10(-)(12) exp((794 +/- 12S)/T)] cm(3) molecule(-1) s(-1). The rate coefficients (in units of cm(3) molecule(-1) s(-1)) at 298 K were measured to be k(298K)(M2MP+Cl) = (4.61 +/- 1.28) X 10(-11) and k(268-363K)(M2MB+Cl) = (9.44 +/- 1.90) X 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.