I. Homoconjugation in Some 7-Chloronorbornane Derivatives. II. Electrostatic Effects in Some 7-Chloronorbornane Derivatives

I. A review of carbonium-ion reactions of bornyl and norbornyl derivatives involving non-classical intermediates and a discussion of various "homoallylic" systems are given. 7-Chloronorbornane and syn-7-chloronorbornene have been found to possess very unreactive chlorine under conditions where exo-norbornyl and cyclopentyl chloride solvolyze readily. In contrast, anti-7-chloronorbornene is quite reactive. The solvolysis of anti-7-chloronorbornene is probably facilitated through stabilization of the carbocationic transition state by electron delocalization analogous to that predicted theoretically for the cyclopropenyl cation. First-order molecular orbital and steric strain calculations provide support for this formulation. Molecular orbital calculations predict a substantial delocalization energy for the carbocation expected from the solvolysis of 7-chlorobicyclo[2.2.1]heptadiene. Several attempts to synthesize this chlorodiene are described. syn-7-Chloro-endo-norbornyl p-toluenesulfonate has been prepared and its acetolysis rate determined. The relative magnitude of the first-order acetolysis rate constant is taken as further evidence for the substantial participation of a non-classical hydrogen-bridged cationic intermediate in the solvolysis of syn- and anti-7-chloro-exo-norbornyl p-toluenesulfonates. II. A review of theoretical and experimental efforts to evaluate the inductive and field effects of substituents on reactivity is presented. Nuclear magnetic resonance spectroscopy has been used to determine the relative base strengths of very weak bases. The rates of bromination of several substituted norcamphors are interpreted in terms of the steric and electrical effects of the substituents. The ultraviolet spectra of a number of substituted norcamohor derivatives are rationalized in terms of the inductive and field effects of the substituents. Several substituted norcamphoroximes have been prepared and their relative acidities measured