Gas-phase reaction of Cl with dimethyl sulfide: Temperature and oxygen partial pressure dependence of the rate coefficient

The kinetics of the reaction of Cl atoms with dimethyl sulfide has been investigated using a relative rate technique. Experiments were performed with oxygen partial pressures of 0, 200, and 500 mbar at a total pressure of 1000 mbar (N-2 + O-2) over the temperature range 283-308 K in a 1080 L reactor using long path in situ Fourier transform infrared absorption spectroscopy to monitor the reactants. The 254 nm photolysis of trichloroacetyl chloride was used as the Cl atom source. Three reference hydrocarbons, cyclohexane, n-butane, and propene were employed. Good agreement was found between the rate coefficients determined using the different reference compounds. The rate coefficients were found to decrease with increasing temperature at constant O-2 pressure and increase moderately with increasing O-2 partial pressure at constant temperature. The temperature dependences of the Cl atom reaction with dimethyl sulfide for the three O-2 partial pressure investigated can be expressed by the simple Arrhenius expressions: k(0) (mbar) (O2) = (4.22 +/- 1.78) x 10(-13) exp((1968 +/- 379)/T), k(200) (mbar O2) = (5.42 +/- 1.85) x 10(-13) exp((1946 +/- 381)/T), and k(500) (mbar) (O2) = (6.90 +/- 2.04) x 10(-13) exp(( 1912 +/- 381)/T). The errors are a combination of the 2sigma statistical errors from the kinetic data analysis plus an estimated systematic error that includes the error in the reference hydrocarbon. The mechanistic implications of the results are discussed. (C) 2004 Wiley Periodicals, Inc.