Chapter 11, Problem 11.47P

Interpretation Introduction

Interpretation:

A complete mechanism is to be drawn for the isomerization of $\text{α-terpineol}$ to $\text{1, 8-cineole}$ and $\text{1, 4-cineole}$ on treatment with the acid is to be drawn.

Concept introduction:

In the presence of a strong acid like ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$, an electron-rich $\text{C}=\text{C}$ is protonated to produce a carbocation. If the double bond is not symmetric, the more substituted, more stable carbocation is preferentially formed. The alcohol oxygen can behave as an electron-rich nucleophilic species because the oxygen atom has two lone pairs. In substrates that contain both $\text{C}=\text{C}$ and an alcohol group, treatment with a strong acid can, therefore, lead to isomerization.