The Norbornyl Cation: Prototype of a 1,3‐Bridged Carbocation

The protracted discussion of whether 2‐norbornyl cations are bridged or unbridged, i.e. nonclassical or classical, has lost most of its meaning, because these terms apply to the extremes of a graded series of structures. This is shown by a study of the solvolysis of stereoisomeric 6‐substituted 2‐norbornyl toluenesulfonates. Norbornyl and other bicyclic cations, to which nucleophiles have limited access, are stabilized by bridging between the cationic center and a saturated carbon atom in the β‐position. Bridging is reduced by electron‐attracting substituents and by bridging.