Chapter 10.7, Problem 5E

Interpretation Introduction

Interpretation:Significance of the dashed bonds in the structure of the non-classical cation should be given and the feature that makes this cation non-classical should be identified.

Concept introduction:A classical carbocation represented as ${\text{H}}_{\text{3}}{\text{C}}^{\oplus }$ has sextet of electron and a vacant p-orbital. They are also referred to as carbenium ion. It is formed by three $s{p}^2$ hybridized orbitals of carbon and $1s$ of three hydrogen atoms overlaps as illustrated below.

  

Classical carbocation prefers to be tri-coordinated and achieve stabilization via hyperconjugation. This indicates that an adjacent $\text{C}-\text{H σ}$ bond or some unshared electron pair can be used to stabilize such carbocation.

A non-classical cation is a unique carbocation that involves the delocalization of electron density of filled bonding orbital over three carbons. It exists for systems such as phenonium ions,norbornyltosylates, brosylate, and nortricyclonium cations. They can be understood as carbocation that is a transition state for two asymmetric equilibrium cations.