Chapter 12, Problem 55P

Interpretation Introduction

Interpretation:

The structure of the product formed by $\text{1,4-addition}$ of bromine to furan is to be determined.

Concept introduction:

Conjugated dienes are hydrocarbons in which two $\text{C=C}$ units are joined by a single bond.

When a diene is treated with a halogen in the presence of a solvent like ${\text{CCl}}_{\text{4}}$, two products are formed. In $\text{1,2-addition}$ product, the two halogen atoms are added to the adjacent carbon atoms.

In $\text{1,4-addition}$ product, the two halogen atoms are added to the carbon atoms $\text{C1 and C4}$.

The allylic carbocation is formed preferably during the first step.

Resonance of this allylic carbocation generates a new carbocation, resulting in the second product.