Chapter 28, Problem 28.38AP

Interpretation Introduction

(a)

Interpretation:

A mechanism for each of the following transformations is to be suggested.

Concept introduction:

The Claisen rearrangement is a part of pericyclic reaction involving carbon-carbon bond formation. This reaction was discovered by Claisen and the reactions deals with the heating of allyl vinyl ether under thermal conditions to furnish an unsaturated carbonyl compound via [3, 3] sigmatropic rearrangement.

Interpretation Introduction

(b)

Interpretation:

A mechanism for each of the following transformations is to be suggested.

Concept introduction:

Electrocyclic reactions are a pericyclic reaction which occur intramolecularly. These reactions will result in the formation of ring compounds under the influence of heat or light. Notably, in this process one new sigma bond is formed and one old π-bond is consumed. Intriguingly, the reverse ring opening electrocyclic reaction can also be possible to occur under the same reaction mechanism but in reverse manner.

Interpretation Introduction

(c)

Interpretation:

A mechanism for each of the following transformations is to be suggested.

Concept introduction:

Generally, Sigmatropic reaction is referred as the migration of allylic sigma bond at one end of the π-electron system to the other end of the π-electron system as an uncatalyzed intramolecular reaction. Though, the position of π-bond is changed in Sigmatropic reaction, the total number of π-bonds remain unchanged. The sigma bond can be cleaved at the middle or at the end of the π-system. The formation of sigma bond at 3, 3-position of a 1, 5-diene is called as cope rearrangement.