Investigation of steric effects on the reactivity of norbornanone-2 by determining the secundary isotopic effects of deuterium

Abstract The following compounds have been prepared: 2‐norbornanone‐3 d 1 exo , ‐3‐ d 1 endo , ‐ 3,3‐ d 2 and 5,6‐ d 2 endo ; the rates of borohydride ion addition and of decomposition of bisulfite addition compounds have been measured in order to explain the high exo side reactivity of norbormyl systems. In both reactions, there is no significant isotope effect due to deuteration at the 5,6 endo positions. This observation can result either from an absence of any steric interaction or from a non‐bonded interaction potential much smaller than usually admitted. The protons in 3‐ endo and 3‐ exo positions are not equivalent towards the nucleophile approach.