Theoretical investigations on the kinetics of Cl atom initiated reactions of series of 1-alkenes

Abstract

The temperature-dependent rate coefficients were calculated for the reactions of Cl atoms with propene (R₁), 1-butene (R₂), 1-pentene (R₃), and 1-hexene (R₄) over the temperature range of 200–400 K. Canonical variational transition state theory (CVT) with small curvature tunneling (SCT) and conventional transition state theory (CTST) in combination with MP2/6-31G(d,p), MP2/6-31G+(d,p), and MP2/6–311 + G(d,p) level of theories were used to calculate the kinetic parameters. The obtained rate coefficients at 298 K for the reactions of Cl atoms with propene, 1-butene, 1-pentene, and 1-hexene are 1.36 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, 1.53 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, 4.61 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, and 4.76 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, respectively. In all these reactions, strong negative temperature dependence was observed over the studied temperature range. Cl atom addition across the double bond is the most dominant pathway. The contribution of abstraction channels towards their global rate coefficients was observed to be increasing from propene to 1-hexane. Atmospheric implications such as effective lifetimes and thermodynamic parameters of the test molecules were investigated in the present study.