Chapter 11, Problem 11.18P

Interpretation Introduction

Interpretation:

The conjugated diene that was used as the reactant, which leads to the formation of each of the given products, is to identified, and the complete, detailed mechanism is to be given.

Concept introduction:

The electrophilic addition reaction in a case of conjugated diene system leads to the formation of a mixture of the isomeric products that are 1, 2-addition and 1, 4-addition products. The major products in 1, 2-addition and 1, 4-addition depend on the stability of the carbocation formed as the reaction intermediate. The most stable carbocation gives the major 1, 2-addition and 1, 4-addition products. The stability order for carbocation is Secondary benzylic > Tertiary > Primary benzylic, allylic > Secondary > Primary > Methyl etc. The 1, 2-addition occurs according to Markovnikov rule, and the 1, 4-addition is the conjugate addition across the double bond by shifting the double bond in the resonating structure of the same carbocation.