Chapter 11, Problem 11.43P

Interpretation Introduction

Interpretation:

The products that are result of $\text{1, 2- addition}$ and $\text{1, 4-addition}$ are to be identified.

Concept introduction:

A conjugated diene undergoes an electrophilic addition with Bronsted acids and yields a mixture of isomeric products. Both products are produced from the same carbocation intermediate. The intermediate has two resonance structures, one with a positive charge on C2 and one with a positive charge on C4. In the resonance hybrid, therefore, each of those two C atoms bears a partial positive charge, so each can be attacked by anions. The ${\text{H}}^{\text{+}}$ and anion, if added to the diene to produce an halo alkene separated by two C atoms, makes it the product of 1, 2-addition. On the other hand, another is the product of 1, 4-addition as the ${\text{H}}^{\text{+}}$ and anion added to the diene are separated by four C atoms.