Chapter 11, Problem 11.25P

Interpretation Introduction

Interpretation:

All possible structures of the compound ${\text{C}}_{\text{5}}{\text{H}}_{\text{8}}$, which produces the compound ${\text{C}}_{\text{5}}{\text{H}}_{\text{9}}\text{Cl}$ when treated with excess HCl, are to be drawn.

Concept introduction:

In an electrophilic addition reaction, a Bronsted acid adds across a double bond as a proton and the conjugate base. It is a two-step reaction. The $\text{π}$ bond breaks heterolytically and forms a bond with the proton from the acid. This produces a carbocation intermediate. Generally, the proton adds to the less substituted carbon of the initial double bond, producing a more substituted, and hence, a more stable carbocation. The carbocation may rearrange via a $\text{1, 2-hydride}$ or a $\text{1, 2-methyl}$ shift, or via resonance stabilization, if this leads to a more stable carbocation. In the second step, the conjugate base acts as a nucleophile and forms a bond with the carbocation to give the product.