However, the quantum yield for CH3SNO formation17 in (CH3S)2 photodissociation in the presence of NO is 2.04 ± 0.06 so that reaction 21 consumes, at most, a few percent of the CH3S. Until further work is performed, it seems reasonable to assume that reaction 18 plays a minor role in the C2H5S + NO system.C1HiS + 02, H2, CH4, C2H4. No reaction could be found with any of these gases. When 02 additions up to 1.3 X 1019 molecules cm"3 were used, an upper limit for the rate coefficients with 02 was 2 X 10"17 cm3 molecule"1 s"1. A similar upper limit has been established9 for CH3S + 02. An even lower value has been established6 as the upper limit for HS + 02 (4 X 10"19 cm3 molecule"1 s"1). No reaction with H2 or CH4 (rate coefficients <10"16 cm3 molecule"1 s"1) is not surprising since the reactions C2H5S + H2 -CjHjSH + AH =12 kcal mol"1 ( 22) C2H5S + CH4 -C2H5SH + CH3 AH = 13 kcal mol"1 (23) have large endothermicities.Alkylthio radicals are known to be effective at inducing isomerization of olefins,35 and a rate coefficient of 8 X 10"15 cm3 (35) Sivertz, C. J. Phys. Chem. 1959, 63, 34. molecule"1 s'1 has been deduced36 for CH3S attack on ethylene.In this study, an upper limit of 10"15 cm3 molecule"1 s"1 was found for the removal of C2H5S by C2H4. The observation of efficient isomerization and comparitively inefficient removal is consistent with the earlier conclusion36 that alkylthio radical attack on a double bond is reversible.Although the rate coefficient for the reaction of C2H5S with 02 is <2 X 10"17 cm3 molecule"1 s"1, a determination of the actual value (or an upper limit in the 10"19 cm3 molecule"1 s"1 range) will be necessary before the fate of C2H5S radicals in the troposphere will be determined. This is because the tropospheric abundance of 02 is = 108 times that of NO and N02, so that a rate coefficient as low as 10"18 cm3 molecule"1 s"1 could still suffice to make C2H5S + 02 the dominant tropospheric removal reaction for C2H5S radicals.
A recent paper "Quenching of o(ls) by 02 (alA g), by T.G. Slanger and G. Black was inadvertantly omitted from the table of contents. The correct reference is Geophysical Research Letters, Vol. 8, No. S, pages S5S-S58.
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