Examination of Y-Deterium isotope effects for the solvolysis of model isoprenoid compounds

Model isoprenoid compounds can undergo two distinct pathways, dissociative or associative nucleophilic substitution depending on the conditions used. The dissociative pathway consists of two steps, involving a carbocation intermediate where the formation of that carbocation is rate determining. The associative pathway is concerted reaction, which does not involve carbocation formation and the rate is more governed by the strength of the attacking nucleophile. Solvolysis Reactions of the deuterium substituted model compounds are typically slower than protiated compounds when comparing the reaction rates. So the sensitive kinetic isotope effect (KIE) can be used to evaluate the dissociative or associative nature of these reactions. A kinetic isotope effect will indicate the presence of positive charge build up adjacent to CD3 (see figure 1). So kH/kD values will be measured for model associative nucleophilic substitution reactions, I would expect an associative KIE value to equal one, indicating little or no positive charge accumulation during the reaction.