The conventional flash photolysis-resonance fluorescence technique was employed to study reactions of OH with CH3SCH3 (1), CD3SCD3 (2), CH3SC2H5 (3), and C2H5SC2H5 (4) in argon buffer gas. Reactivity trends, temperature dependencies, and isotope effects suggest that hydrogen abstraction is the dominant observed reaction pathway under these conditions. A pulsed-laser photolysis-pulsed-laser-induced fluorescence technique was employed to study reactions 1 and 2 in N2, air, and O2 buffer gases. Complex kinetics were observed in the presence of O2. A four-step mechanism involving hydrogen abstraction, reversible addition to the sulfur atom, and scavenging of the (thermalized) adduct by O2 is required to explain all experimental observations. In 1 atm of air, the effective bimolecular rate constant for reaction 1 decreases monotonically from 1.58 × 10-11 to 5.2 × 10-12 cm3 molecule-1 s-1 over the lower tropospheric temperature range 250-310 K. Over the same temperature range the branching ratio for hydrogen abstraction increases monotonically from 0.24 to 0.87. At 261 K, the rate constant for unimolecular decomposition of the CD3S(OH)CD3 adduct is (3.5 ± 2.0) × 106 s-1 and the rate constant for the adduct reaction with O2 is (4.2 ± 2.2) × 10-12 cm3 molecule-1 s-1.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of physical chemistry|
|State||Published - Dec 1 1986|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry