Chapter 12, Problem 12.58P

Interpretation Introduction

Interpretation:

A mechanism is to be proposed for the formation of $\text{cyclohepta-1, 3, 5-triene}$ when benzene is treated with diazomethane and irradiated with light.

Concept introduction:

When diazomethane is irradiated with light, the $\text{C}-\text{N}$ bond undergoes heterolysis to produce carbene and a very stable nitrogen molecule. The carbene is a species with a lone pair on the carbon and an incomplete octet. This means it behaves as both an electrophile and a nucleophile. As a result, it can add across a double bond, usually forming a cyclopropyl ring. The three-membered ring is highly strained and can undergo ring expansion.