No abstract

The gas phase reactions of S(1D2) and S(3PJ) atoms with alkynes have been studied by photolyzing COS in the presence of CH≡CH, CF3C≡CH, and CF3C≡CCF3. In the reactions with CH≡CH, CS2, benzene, and thiophene were formed; with CF3C≡CH, eight products were found with disubstituted thiophenes and trisubstituted benzenes as the major products. In the case of CF3C≡CCF3, only perfluorotetramethylthiophene was detected at low conversion but at long photolysis several new products were observed. Many of the reaction products characterized here have not been reported before.The formation and distribution of the reaction products could be rationalized by an overall mechanism in which the formation of the highly reactive primary adducts, thiirene and thioformylmethylene, is followed by bimolecular reactions yielding the principal end products. The formation of minor products could be explained by secondary photoisomerizations, secondary photolysis, and by secondary decompositions and the secondary reactions of sulfur atoms with primary products.

The gas phase reactions of both S('D) and S(?P) atoms with propadiene afford methylenethiirane in nearly quantitative yields at high pressure. With 1,2-butadiene the three novel unsaturated isomeric thiirane products, resulting from addition to the 2,3 double bond and cis-and trans-addition to the 1,2 double bond, have been characterized. The yields are pressure and exposure-time dependent and, at zero conversion and high pressures, comprise -94% of the C4H,S adducts, the remainder being two thiol insertion products. The ratio of 2,3-addition to 1,2-addition is -1.3 for S('D) atoms and -2.1 for S(?P) atoms.Rate parameters for the S(") + 1.2-butadiene reaction were determined in competition with the S(?P) + I-C,H, reaction and found to be A = 6.4 + I. l X 10"' M -' s-' and E, = 1.4 + 0.2 kcal mol-'. The E,,'s associated with 1.

Durch UV‐Photolyse von COS in situ erzeugtes S(1D2) reagiert mit Ethylen zu Thiiran und Vinylthiol (Gesamtausb 100%).