A comprehensive gas-phase kinetics of α-methyl thiophene with Cl-atom and OH-radical: Experimental and theoretical studies

The rate coefficient for the reaction of methyl thiophene (MeTp) with Cl atom was measured to be (1.09 +/- 0.24) x 10(-10) cm(3) molecule(-1)s(-1) at 298K and 760 Torr using the relative rate (RR) method. The experimental temperature-dependent rate coefficient was measured to be k(T)(258-358K )= (2.08 +/- 0.10) x 10(-11 )exp [(484.5 +/- 15.4)/T] cm(3) molecule(-1) s(-1). The theoretical rate coefficients for the reaction of MeTp with Cl-atom and OH radical were calculated at BD(T)/VDZ//BHandHLYP/6-31+g & lowast; and BD(T)/AVDZ//M06-2X/6-311++g & lowast;& lowast; level of theory respectively. The Arrhenius equation from the theoretically calculated rate coefficients for MeTp + Cl using the MESMER simulation was obtained to be k(T)(MeTp+Cl)(200-400K )= (2.44 +/- 0.12) x 10(-11 )exp [(438.2 +/- 14.9)/T] cm(3) molecule(-1) s(-1). The experimental and theoretical rate coefficients show a negative temperature dependence behaviour over the studied temperature range. The rate coefficient for MeTP + OH was calculated as k(T)(200-400)(KCVT/SCT )= (2.83 +/- 0.20) x 10(-13 )exp[(1641.7 +/- 20.6)/T] cm(3) molecule(-1) s(-1) from CVT/SCT methods. Following the MESMER simulation for MeTp + OH reaction, the Arrhenius expression was found to be k(T)(MeTp+OH)(200-400K )= (8.31 +/- 0.53 )x 10(-12)exp [(588.9 +/- 19.2)/T] cm(3) molecule(-1) s(-1). At 298 K, the rate coefficient was calculated to be 5.60 x 10(-11) cm(3) molecule(-1) s(-1) and 6.23 x 10(-11) cm(3) molecule(-1) s(-1) for the reaction of MeTp with OH from CVT/SCT method and MESMER simulations. Both calculation methods demonstrated a negative temperature dependency over the temperature range of 200-400 K. No pressure dependency was observed over the 5-760 Torr in the MESMER calculations. The atmospheric lifespan of MeTp was estimated to be similar to 100 days in ambient conditions and similar to 1 day in polluted or coastal areas.