Ring opening reaction of the trans -cyclobutene isomer shown takes place readily at a lower temperature than a similar ring opening of the cis -cyclobutene isomer. This temperature effect is to be explained and the stereochemistry of each reaction, conrotatory or disrotatory, is to be identified. 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.

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Chapter 30.SE, Problem 35AP

Interpretation Introduction

Interpretation:

Ring opening reaction of the trans-cyclobutene isomer shown takes place readily at a lower temperature than a similar ring opening of the cis-cyclobutene isomer. This temperature effect is to be explained and the stereochemistry of each reaction, conrotatory or disrotatory, is to be identified.

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.

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