Molecular Dynamics of the Norbornyl Cation in Solution and Its Generation in Winstein-Trifan Solvolysis: The Timing of Sigma Bridging.

Molecular dynamics simulations were performed on the solvolyses of exo - and endo -norbornyl brosylate and for the "nonclassical" σ-bridged norbornyl cation in an acetic acid solution. This computational modeling of the original Winstein-Trifan experiment confirms that exo -solvolysis is accompanied by σ-bridging in the transition state, while endo -solvolysis is not; σ-bridging eventually occurs in a dynamically stepwise fashion. Simulations of the norbornyl cation in solution show typical vibrations due to zero-point and thermal vibrations but no tendency to sample localized "classical cation" geometries.