REACTIVITY SELECTIVITY RELATIONSHIP AND KINETIC SOLVENT ISOTOPE EFFECTS IN NUCLEOPHILIC-SUBSTITUTION REACTIONS

Selectivity plots, log(k(X1)/k(X2)) vs. sigma(Y), have been obtained f or various nucleophilic substitution reactions: (i) with anilines (N) in methanol (S), k(N)/k(S), using literature data for YC6H4CH2Cl, YC6H 4COCl, YCH4SO2Cl, YC6H4COCH2Br, YC6H4CH(CH3)Cl and YC6H4CH[C(CH3)3]OSO 2C6H4NO2; and (ii) with kinetic solvent isotope effects (KSIE) in wate r and methanol, k(SOH)/k(SOD), determined in this work for the same co mpounds (except for the latter two). The two selectivity plots are sho wn to be equivalent in applying mechanistic criteria based on four rea ctivity-selectivity regions identified by the slopes of the selectivit y plots, DELTArho(Y). Straightforward applications were possible in mo st cases except for the aminolysis of phenacyl bromides and 1 -phenyle thyl chlorides. For these two, detailed analyses of kinetic results we re required, in addition to the reactivity-selectivity considerations, before deciding the reaction mechanism.