Rate coefficients for the room temperature reaction of Cl atoms with dimethyl sulfide and related alkyl sulfides

Abstract

Rate coefficients for the reaction of Cl atoms with a selection of alkyl sulfides have been determined using the relative rate technique at 298 ± 3 K. Based on an absolute value of 1.94 × 10^–10 cm³ molecule^–1 s^–1 for the reaction of Cl with n-butane, the following values for the reaction-rate coefficients were determined in the presence of nitrogen (in units of 10^–10 cm³ molecule^–1 s^–1) to be: dimethyl sulfide, 3.61 ± 0.21; ethylmethyl sulfide, 4.89 ± 0.29; diethyl sulfide, 5.98 ± 0.23; and dipropyl sulfide, 7.02 ± 0.81. The relative-rate experiments were conducted in an atmosphere of either nitrogen or synthetic air to investigate the effect of the presence of oxygen on the rate coefficient; only the rate coefficient for the reaction of Cl with dimethyl sulfide showed an appreciable difference, yielding a value of (4.19 ± 0.16)× 10^–10 cm³ molecule^–1 s^–1. Further experiments were undertaken to measure the relative-rate coefficients of the series of alkyl sulfides using cyclohexane as the reference compound. In most cases, the value of k_sulfide/k_n-butane divided by the value of k_sulfide/k_cyclohexane produced a value of k_cyclohexane/k_n-butane consistent with our experimentally determined value of k_cyclohexane/k_n-butane= 1.69 ± 0.04. The results are discussed with respect to the literature data, structure activity relationships, chemical mechanisms and the chemistry of the marine atmosphere.