DISCHARGE FLOW STUDY OF THE REACTIONS OF CHLORINE AND FLUORINE-ATOMS WITH DIMETHYL SULFIDE

Discharge-flow mass spectrometric study of Cl/Cl-2/DMS and F/DMS/(Cl-2 or Br-2) chemical systems was performed at low pressure (similar to 1 Torr of helium) and 298 K. In these systems the primary organic radic als of the Cl + DMS and F + DMS reactions were titrated by reaction wi th Cl-2 or Br-2. It was confirmed that the reaction Cl + DMS proceeds through the unique channel Cl + CH3SCH3 --> HCl + CH3SCH2 (1a). In con trast, two channels were found for the reaction F + DMS: F + CH3SCH3 - -> HF + CH3SCH2 (2a) and F + CH3SCH3 --> CH3SCH3 --> CH3 (2b) with bra nching ratio (2a):(2b) = 0.8:0.2. Kinetic measurements were also perfo rmed yielding the following rate constants at 298 K: F + DMS --> produ cts (2), k(2) = (2.4 +/- 0.4) x 10(-10) cm(3) molecule(-1) s(-1); CH3S CH2 + Cl-2 --> CH3SCH2Cl + Cl (6), k(6) = (7.1 +/- 2.0) x 10(-12) cm(3 ) molecule(-1) s(-1). The rate constant of the reaction CH3SCH2 + CH3S CH2 + M --> (CH3SCH2)2 + M (11) was estimated, k(11) = 2.5 x 10(-11) c m(3) molecule(-1) s(-1) (P = 1 Torr of He).