THROUGH-BOND TRANSMISSION OF SUBSTITUENT EFFECTS IN THE BICYCLO[2.2.2]OCTANE RING-SYSTEM - SOLVOLYSIS OF 4-DEUTERIO (SI(CH3)3,GE(CH3)3,SN(CH3)3)-SUBSTITUTED AND 4-METALLOIDAL (SI(CH3)3,GE(CH3)3,SN(CH3)3)-SUBSTITUTED BICYCLO[2.2.2]OCT-1-YL PARA-NITROBENZENESULFONATES AND METHANESULFONATES

4-Deuterio- and 4-metalloidal (M(CH3)3, M = Si, Ge, and Sn)-substituted bicyclo[2.2.2]oct-1-yl p-nitrobenzenesulfonates and methanesulfonates, respectively, have been synthesized, and their solvolyses at 25 °C in aqueous ethanol and trifluoroethanol solvents have been examined. An extraordinarily large δ-deuterium isotope effect (kH/kD) is observed. Moreover, large rate enhancement factors are observed for the metalloidal substituents. These findings indicate through-bond coupling (or double hyperconjugation) to be a significant mode of cation stabilization in the bicyclooctyl system. The formation of some fragmentation product in a subsequent step is an analogous manifestation of the proposed long-range electronic interaction © 1993, IEEE. All rights reserved. © 1990, American Chemical Society. All rights reserved.