An Exprimental and Computational Study on the Cl Atom Initiated Photo-Oxidization Reactions of Butenes in the Gas Phase

Abstract

Temperature-dependent rate coefficients for the reactions of Cl atoms with trans-2-butene and isobutene were measured over the temperature range of 263-363 K using relative rate technique with reference to 1,3-butadiene, isoprene, and 1-pentene. The measured rate coefficients for the reactions of Cl atoms with isobutene and trans-2-butene are k= (3.43 ± 0.11) × 10 and k = (3.20 ± 0.04) × 10 cm molecule s, respectively, at 298 K and 760 torr. Measured rate coefficients were used to fit the Arrhenius equations, which are obtained to be k = (4.99 ± 0.42) × 10 exp[(584 ± 26)/T] and k = (1.11 ± 0.3) × 10 exp[(291 ± 88)/T] cm molecule s for isobutene and trans-2-butene, respectively. To understand the reaction mechanism, estimate the contribution of each reaction site, and to complement our experimental results, computational studies were also performed. Canonical variational transition state theory with small curvature tunneling in combination with MP2/6-31G(d), MP2/6-31G(d,p), MP2/6-31+G(d,p), CCSD(T)/cc-pvdz, and QCISD(T)/cc-pvdz level of theories were used to calculate the temperature-dependent rate coefficients over the temperature range of 200-400 K. The effective lifetimes, thermodynamic parameters, and atmospheric implications of the test molecules were also estimated.

Kinetics of the Reactions of Chlorinated Very Short-Lived Substances (VSLSs) with Chlorine Atoms

“…The present results for C 2 HCl 3 + Cl are consistent with the C 2 H 2 Cl 2 + Cl reaction in the literature, where it was demonstrated for the addition of Cl to C 2 H 2 Cl 2 that the bridged intermediate (addition followed by elimination) pathway is more favored kinetically, and the abstraction pathway is negligible. Vijayakumar et al (2017) also reported mechanisms for the Cl atom addition to substituted alkenes, showing domination of the addition reaction, which is consistent with the present study.…”

Tropospheric Photo-oxidation of Ethyl Methacrylate Initiated by Cl Atoms in the Gas Phase: Kinetic and Mechanistic Investigations

“…They reported the temperature dependent rate coefficient and at 298 K as k 1,3‑butadiene+Cl 269–363K = (1.05 ± 0.19) × 10 –10 exp [(332 ± 56)/ T ] cm 3 molecule –1 s –1 and (3.31 ± 0.48) × 10 –10 cm 3 molecule –1 s –1 , respectively. The rate coefficient for the reaction of trans -2-butene with Cl atoms reported by Vijayakumar et al has been used in this study. They used RR method to calculate the temperature dependent rate coefficients in the temperature range of 269–363 K. 1,3-Butadiene and isoprene were used as a reference compounds to measure the rate coefficients.…”

Kinetic Investigations on the Gas Phase Reaction of 2,2,2‐Trifluoroethylbutyrate with OH Radicals: An Experimental and Theoretical Study

“…calculated the lifetime of the test molecule due to its reaction with OH radicals and reported as 4 days (k OH =1.3×10 −12 cm 3 molecule −1 s −1[13] at 298 K, [OH]=2×10 6 radicals cm −3[40] were used in their calculations), which is in excellent agreement with our estimated lifetime (3.7 days) using the experimentally measured rate coefficient (k OH = 1.58×10 −12 cm 3 molecule −1 s −1 at 298 K, present study). The cumulative atmospheric lifetime for the test molecule was calculated with respect to their reactions with OH radicals and Cl atoms using the following equation …”

“…The optimized geometries of all the stationary points [reactant, pre‐reactive complexes, transition states (TSs), product complexes and products] were optimized at the M06‐2X level of theory with the 6–31+G(d,p) basis set. M06‐2X method provides reliable results for the reactions of analogues to the title reaction . The unrestricted formalism was used for all the stationary points of the open‐shell TS and radicals.…”