Solvolytic Reactivities of Some 7-Chloronorbornane Derivatives¹

Abstract

7-Chloronorbornane, a number of saturated 7-chloronorbornane derivatives and syn-7-chloronorbornene have been found to possess very unreactive chlorine under conditions where exo-norbornyl and cyclopentyl chlorides solvolyze readily. In contrast, anti-7-chloronorbornene (like anti-7-norbornenyl p-toluenesulfonate, Winstein, Woodward and co-workers) is quite reactive and solvolyzes about 55 times more rapidly than exo-norbornyl chloride and about 7 times more rapidly than ɑ-methylallyl chloride in 80% ethanol at 100º. 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. The very low reactivity of syn-7-chloronorbornene and 7-chloronorbornane derivatives may be accounted for on the basis of steric inhibition of hyperconjugation.