Chapter 11, Problem 11.57P

Interpretation Introduction

Interpretation:

The mechanism for the given reaction is to be proposed.

Concept introduction:

The dienes are the compounds containing two double bonds. These two double bonds may or may not be conjugated. The non-conjugated dienes undergo electrophilic addition reactions in the presence of a strong acid. The first step is the protonation of the double bond, which would form the most stable carbocation intermediate. This generates the conjugate base of a strong acid, which can serve as a nucleophile. The addition of proton across the double bond follows Markovnikov’s rule. In this, the proton gets attached to the carbon atom in the double bond, which is least substituted or has greater number of hydrogens attached. For long chain isolated dienes, an intramolecular reaction may take place in which the other double bond serves as a nucleophile and attacks the carbocation intermediate within the same compound. The driving force for this step is the formation of stable five or six membered ring. In the third step, the conjugate base produced in the first step serves as a nucleophile and attacks the carbocation to yield the final product.