Date of Award
Union College Only
Bachelor of Science
The photochemical reduction of benzophenone to benzopinacol has been known since the early part of this century when it was first discovered by Ciamician and Silber (4). The reaction is used today as a convenient preparation of benzopinacol. Benzophenone dissolved in isopropyl alcohol is placed in bright sun light and allowed to stand. After several hours the first crystals of benzopinacol begin to separate and within a few days the reaction is complete (13). The reaction proceeds through a photoexcited state of benzophenone. The excited intermediate abstracts hydrogen from the solvent (isopropyl alcohol) to form the diphenylhydroxymethyl radical and a solvent radical. Finally, two diphenylhydroxymethyl radicals dimerize to form benzopinacol. In the presence of an alkaline alkoxide the benzopinacol is cleaved and forms benzhydrol with regeneration of benzophenone (7). Benzohydrol can, therefore, be produced photochemically by the addition of an alkaline material to the original solution. Benzopinacol is produced but is immediately cleaved to benzohydrol. The regenerated benzophenone is reconverted to benzopincacol and the process repeats until the benzophenone is consumed. Reaction (A) has been modified by the addition of cyclohexene to the benzophenone-isopropanol solution before exposure to sunlight. It has been the purpose of this work to determine the identity of the product formed by the modified reaction.
Heimlich, Robert Michele, "Studies in photoexcited ketone systems" (1962). Honors Theses. 1923.