Secondary α-deuterium isotope effects on borohydride reductions and on the protonation of benzaldehyde

As part of a general investigation of secondary α-deuterium isotope effects on addition reactions, the reduction of benzaldehyde and benzaldehyde-d with sodium borohydride, sodium cyanoborohydride, and borane-morpholine have been studied. The preliminary results reported indicate substantial isotope effects which suggest that interaction of the reagent with the carbonyl carbon is fairly well advanced in the transition state. (U.K.)