Tunable diode laser spectroscopic detection of formaldehyde (H 2 CO) and HCl coupled with laser flash photolysis of Cl 2 CO–CH 3 SCH 3 –O 2 –N 2 mixtures, in both the presence and absence of NO, has been utilized to conduct a mechanistic and kinetic investigation of the atmospheric oxidation of the CH 3 SCH 2 radical, a product of dimethyl sulfide (DMS, CH 3 SCH 3 ) reactions with OH and NO 3 in the atmosphere. The temperature dependence of the CH 3 SCH 2 O 2 + NO rate coefficient (k 2 ) and the 298 K rate coefficient for the CH 3 SCH 2 O 2 self reaction (k 4 ) have been measured. The Arrhenius expression k 2 = 4.9 × 10 −12 exp(263/T) cm 3 molecule −1 s −1 adequately summarizes our CH 3 SCH 2 O 2 + NO kinetic data over the temperature range 261–400 K. Contributions from side reactions, which are not completely quantifiable, limit the accuracy of the k 4 (298 K) determination; our results indicate that the true value for this rate coefficient is within the range (1.2 ± 0.5) × 10 −11 cm 3 molecule −1 s −1 . In both reactions CH 3 SCH 2 O 2 is converted to H 2 CO with unit yield (at T = 298 K). Our results demonstrate that the lifetime of CH 3 SCH 2 O, a proposed precursor to H 2 CO, is less than 30 µs at 261 K and 10 Torr total pressure.
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Urbanski et al. (1997) studied this question.