The SO2(3B1) photosensitized isomerization of cis- and trans-1,2-dichloroethylene

✍ Scribed by Fred B. Wampler; Jan W. Böttenheim

• Publisher: John Wiley and Sons
• Year: 1976
• Tongue: English
• Weight: 635 KB
• Volume: 8
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550080412

✦ Synopsis

The photolysis of SOz at 3712 A in the presence of the 1,2-dichloroethylenes has been investigated at 22°C. The data are consistent with the SOz( 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 SOz( 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 =k 0.26 and to the transisomer with a 0.37 + 0.16 probability. Quenching rate constants for removal of SOz(3B1) molecules by cis-and trans-1 ,2-dichloroethylene have been estimated from quantum yield data %nd from laser excited phosphorescence lifetimes using an excitation wavelength of 3130 A. Estimates of the quenching rate constant (units of l./mole.sec) are for the cis- isomer, (1.63 + 0.71) X lo'", quantum yield data, and (2.44 f 0.11) X lolo, lifetime data; and for the trans-isomer, (2.59 f 0.09) X IO'O, lifetime data, and (2.35 i 0.89) X 101O. quantum yield data. An experimentally determined photostationary composition,

[cis-C~ClzH~]/[trans-CzCl~Hz]

= 1.8 + 0.1, was in good agreement with a value of 2.00 f 1.15 which was predicted from rate constants derived in this study.