Part I. Photosensitized isomerization. Part II. Photosensitized dimerization

Citation

Turro, Nicholas J. (1963) Part I. Photosensitized isomerization. Part II. Photosensitized dimerization. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Y47D-AH86. https://resolver.caltech.edu/CaltechETD:etd-07162004-111757

Abstract

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cis[...]trans isomerization of the piperylenes (1,3-pentadienes), the 1,2-dichloroethylenes, and the 2-pentenes occurs in the presence of photosensitizers, mainly carbonyl compounds. The results form a coherent pattern if it is assumed that the key step is transfer of triplet excitation, which occurs on every collision between carbonyl triplets and a second molecule provided that transfer is exothermic. Endothermic transfers may occur but only with reduced efficiency.

Butadiene, cyclopentadiene, and cyclohexadiene are dimerized by irradiation in the presence of various photosensitizers. The relative yields of butadiene dimers are dependent upon the photosensitizer employed; however, the relative yields of cyclic diene dimers shows no corresponding dependence. The results are consistent with the assumption that energy transfer to the two conformers of butadiene produces two stereoisomeric, non-interconvertible triplets.

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