Chapter 30.SE, Problem 40AP

Interpretation Introduction

Interpretation:

The observation that a compound having a cyclobutane ring fused to a five membered ring is heated, [1Z,3Z]-1,3-cycloheptadiene is formed while a compound having a cyclobutane ring fused to an eight membered ring is heated, [1E,3Z]-1,3-cyclodecadiene is formed is to be explained. Further why opening of the eight membered ring occurs at low temperature is to be explained.

Concept introduction:

An electrocyclic reaction involves the cyclization of a conjugated acyclic system. These reactions are reversible and are highly stereospecific.

In elecrocyclic reactions involving even number of electron pairs, a thermal reaction occurs in conrotatory manner and a photochemical reaction occurs in disrotatory manner.

In elecrocyclic reactions involving odd number of electron pairs, a thermal reaction occurs in disrotatory manner and a photochemical reaction occurs in conrotatory manner.