Photochemical α Cleavage of Benzoin Derivatives. Polar Transition States for Free-Radical Formation

F. D. Lewis, R. T. Lauterbach, H. G. Heine, W. Hartmann, H. Rudolph

Research output: Contribution to journalArticlepeer-review

141 Scopus citations


The photochemical α cleavage reactions of benzoin, benzoin ethers, benzoin acetate, and several related phenyl ketones have been investigated, α cleavage is the only primary process observed for benzoin and the benzoin alkyl ethers in benzene solution, β cleavage is a minor competing reaction for benzoin phenyl ether. Substituents at the a carbon have little effect on the efficiency (quantum yield) of cleavage; however, they have a pronounced effect on the rate constant for cleavage. Benzoin alkyl ethers are about 105 times more reactive toward α cleavage than deoxybenzoin. Substituents capable of stabilizing an adjacent positive charge are far more effective in accelerating a cleavage than are substituents capable of stabilizing free radical centers. It is concluded that the transition state for α cleavage has considerable ionic character and does not resemble the free radical products.

Original languageEnglish (US)
Pages (from-to)1519-1525
Number of pages7
JournalJournal of the American Chemical Society
Issue number6
StatePublished - Mar 1 1975

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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