PREDICTION OF SN2 TRANSITION-STATE VARIATION BY THE USE OF MORE OFERRALL PLOTS

The More O'Ferrall and Thornton approaches for prediction of the effects of reactant variation on transition-state structure are applied to direct displacement reactions on benzyl derivatives. Experimental measures of transition-state structure are derived from the α-deuterium isotope effects, the response to solvent ionizing power (m values), the kOTs/kCl ratio, and the kEtOH/kH2O ratio. Complications in interpretation of the leaving-group ratio resulting from steric effects are discussed, and it is shown that there is a small electronic effect on this ratio. Also, potential-energy diagrams are used to demonstrate that there are certain instances in which a change in reactivity should not be accompanied by a change in selectivity. © 1979, American Chemical Society. All rights reserved.