QUANTITATIVE STUDIES IN STEREOCHEMISTRY .B. PHOTOCHEMISTRY .2. SOLVENT AND BASICITY EFFECTS ON RATIO OF DIASTEREOMERIC GLYCOLS FORMED IN ULTRAVIOLET-PROMOTED BIMOLECULAR REDUCTION OF ACETOPHENONE-7-C14 AND BENZALDEHYDE-7-C14

Substitution of various media for the 2-propanol customarily employed in the photopinacolization of acetophenone produced small but real changes in the ratio of dl/meso diastereomers formed. Values from 1.03 (cyclohexane) to 1.31 (50% aqueous 2-PrOH) were observed. In the presence of strong base in 2-propanol, dl/meso ratios as high as 3:1 were found. It is proposed that the more stereoselective reactions in base result from the combination of radical anions with ketyl radicals. The dl/meso ratios for benzaldehyde were observed to be lower than those for acetophenone under identical reaction conditions. The glycols proved stable to the strongly alkaline reaction conditions. © 1968, American Chemical Society. All rights reserved.