The SO2(3B1) photosensitized isomerization of cis- and trans-1,2-dichloroethylene |
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Authors: | Fred B Wampler Jan W Bttenheim |
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Institution: | Fred B. Wampler,Jan W. Böttenheim |
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Abstract: | The photolysis of SO2 at 3712 Å in the presence of the 1,2-dichloroethylenes has been investigated at 22deg;C. The data are consistent with the SO2(3B1) photosensitized isomerization of the 1,2-dichloroethylene isomer. A kinetic treatment of the initial quantum yield data was consistent with the formation of a polarized charge-transfer intermediate whenever SO2(3B1) molecules and one of the 1,2-dichloroethylene isomers collide which ultimately decays unimolecularly to the cis-isomer with a probability of 0.70 ± 0.26 and to the trans-isomer with a 0.37 ± 0.16 probability. Quenching rate constants for removal of SO2(3B1) molecules by cis- and trans-1,2-dichloroethylene have been estimated from quantum yield data and from laser excited phosphorescence lifetimes using an excitation wavelength of 3130 Å. Estimates of the quenching rate constant (units of 1./mole ± sec) are for the cis-isomer, (1.63 ± 0.71) × 1010, quantum yield data, and (2.44 ± 0.11) × 1010, lifetime data; and for the trans-isomer,(2.59 ± 0.09)×1010, lifetime data, and (2.35 ±0.89) × 1010, quantum yield data. An experimentally determined photostationary composition,cis-C2Cl2H2]/trans-C2Cl2H2] = 1.8 - 0.1, was in good agreement with a value of 2.00 - 1.15 which was predicted from rate constants derived in this study. |
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