Chapter 28, Problem 30P

Interpretation Introduction

Interpretation:

The correct product should be identified for the given [1, 3] sigmatropic rearrangement reaction.

Concept introduction:

In a sigmatropic reaction “ one new sigma-bond is formed as another breaks.”

Sigmatropic rearrangement reactions are designated with digits.  For example a [1, 3] sigmatropic rearrangement describe a reaction in which the residue migrates from position 1 to position 3.

[3,3] sigmatropic rearrangement of a 1,3-diene known as Cope rearrangement reaction.

Woodward –Hoffmann rules are the set of rules used to vindicate or predict certain aspects of the stereo chemical outcome and activation energy of pericyclic reactions.

Woodward – Hoffmann rules for sigmatropic rearrangement reactions are listed below

$\begin{array}{ccc}\begin{array}{l}Sumofthenumberofbondsinthereacting\\ sytemsofbothreagents\end{array}& \text{Reaction}\text{conditions}& \text{Allowed}\text{mode}\text{of}\text{bond formation}\\ \text{Even}\text{number}& \text{Thermal}& \text{Antarafacial}\\ & \text{Photochemical}& \text{Suprafacial}\\ \text{Odd}\text{number}& \text{Thermal}& \text{Suprafacial}\\ & \text{Photochemical}& \text{Antarafacial}\end{array}$

Carbon migrating with one lobe of its p orbital interacting

Carbon migrating with both lobe of its p orbital interacting

of configuration is the inversion of a chiral center in a molecule in a chemical reaction.