Spectroscopy and kinetics of the gas phase addition complex of atomic chlorine with dimethyl sulfoxide

Time-resolved UV–vis absorption spectroscopy has been coupled with 248 nm laser flash photolysis of Cl2CO in the presence of CH3S(O)CH3 (and in some cases O2, NO, or NO2) to generate the CH3(Cl)S(O)CH3 radical adduct in the gas phase and study the spectroscopy and kinetics of this species at 296 K. CH3(Cl)S(O)CH3 is found to possess a strong absorption band with λmax = 394 nm and σmax = (4.0 ± 1.4) × 10−17 cm2 molecule−1 (base e); the gas phase spectrum of CH3(Cl)S(O)CH3 is very similar to previously reported liquid phase spectra in chloroalkane and water solvents. Reaction of CH3(Cl)S(O)CH3 with O2 is found to be very slow, and our data suggest that the rate coefficient for this reaction is less than 3 × 10−18 cm3 molecule−1 s−1. Rate coefficients for CH3(Cl)S(O)CH3 reactions with CH3(Cl)S(O)CH3 (k3), NO (k9), and NO2 (k10) in units of 10−11 cm3 molecule−1 s−1 are found to be 2k3 = 6.0 ± 2.4, k9 = 1.2 ± 0.3, and k10 = 2.1 ± 0.3, where the uncertainties are estimates of accuracy at the 95% confidence level.