Triplet state dichloroethylene

Estimates of the triplet energy level of a molecule may be made by observing whether it can accept or transfer energy to several other molecules. Hammond and co-workers42 have shown that ds-trans interconversions of piperylene, 2-pentene, and 1 2 dichloroethylene may be affected by many photosensitizers. The stationary states of the sensitized ds-trans ratios of piperylene with various donors were found to form a coherent pattern if triplet energy transfer was assumed as the key step in the photochemical reaction. From these results they were able to infer the presence and the energies of the triplet states of acetone, phenanthrenequinone, and fluorenone, for which phosphorescence data are not available. The triplet levels were estimated as >70, 65, and 62 kcal./mole, respectively. 

Relatively little work has been done on the photochemistry of the halogenated alkenes. The isomerisation of liquid 1,2-dichloroethylenes irradiated in the singlet-triplet band (A 3130-3660 A) has been studied by Grabowski and Bylina a single triplet state is favoured for both cis and trans isomers. Experiments on the continuous photolysis of gaseous dj-l,2-dichloroethylene with full mercury arc indicate two primary processes, viz., molecular detachment of HCl, and rupture of the C-Cl bond, viz. 

By Cycloadditions involving Thiocarbonyl Compounds. The photocatalysed cycloaddition of thiocarbonyl compounds to olefins to form thietans has been reviewed. The photo-addition of thiobenzophenone to cis- and /m j-dichloroethylene and to cw-dicyanoethylene apparently proceeds with retention of configuration in the olefin moiety. Allenes participate in such reactions, thiobenzophenone with tetramethylallene > and methoxy-allene, for example, giving the thietan derivatives (44) and (45). Thiobenzophenone in its triplet excited state apparently attacks the central... 

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