Reactions of OH and Cl radicals with CH3CN have been studied, at pressures around 1 torr, in discharge flow reactors associated with EPR and mass-spectrometric techniques. For the reaction OH + CH3CN (1), the rate constant found at room temperature, kx = (2.1 ± 0.3) X 10~14 cm1 23 molecule"1 s"1, is in agreement with several flash photolysis-resonance fluorescence determinations obtained at higher pressures (7-300 torr). For the reaction Cl + CH3CN (2), the rate constant measured in the range K shows an Arrhenius behavior in the range 478-723 K, with k2 = (3.46 ± 0.70) X 10"11 exp|(-2785 ± 115)/T| cm3 molecule"1 s"1. At 295 K, the extrapolated value is lower than the experimental one: k2 = (8.89 ± 1.24) X 10"15. These results are discussed and compared with other very recent data. The atmospheric application of these data is discussed, showing that reaction 2 is a negligible atmospheric sink for both CH3CN molecules and Cl atoms.

The reactions of S + OH -SO + H (1) and SO + OH -SO2 + H (2) were studied in a discharge flow reactor coupled to an EPR spectrometer. The rate constants obtained under the pseudo-first-order conditions with an excess of S or SO were found to be k l = (6.6 f 1.4) X lo-" and k p = (8.4 f 1.5) X lo-" a t room temperature. Units are cm3/molec.sec. Besides no reactivity was observed between S and COz a t 298 K and between C10 and SO2 up to 711 K.

The reactions of OH radicals with dimethylsulfide (DMS) diethylsulfide (DES), tetrahydrothiophene (THT), and thiophene have been studied at room temperature for DES and THT, a t 273,293, and 318 K for DMS, and at 293 and 318 K for thiophene by the discharge flow EPR technique in a halocarbon wax coated reactor. The following rate constants were obtained a t room temperature.

The reaction I 0 + CH,SCH, + products (3) was studied at room temperature and near 1 Torr pressure of He, using the discharge flow mass spectrometric technique. The rate constant was found to be k3 = (1.5 * 0.5) x cm3 molecule-' s-'. CH3S(0)CH3 was detected as a product suggesting the following channel: I 0 + CH,SCH,-+ CH3S(0)CH3 + I. The rate constant of the reaction I 0 + I 0 + products (1) was also measured: k, = (3 5 0.5) x lo-" at 298 K and 1 Torr pressure. The atmospheric implication of reaction (3) is discussed. The results indicate that this reaction could be a potential important sink of CH3SCH3 in marine atmosphere.