CD, migration (1.061 per deuterium) and 0.970 for CD3 as the nonmigrating group (0.990 per deuterium). The isotope effect on the migrating group in the Baeyer-Villiger reaction is smaller than expected; the general trend predicts a larger per deuterium isotope effect for RCHz than for CH3. This is consistent with a smaller decrease in the HCH bending force constant or a larger increase in HCO bending force constant for benzyl migration in the ...