Chapter 20, Problem 20.50P

Interpretation Introduction

Interpretation:

Whether an achiral or two equal enantiomeric products would be given has to be predicted in the product of the given reaction and explained with chair like transition state.

Concept Introduction:

Cope-rearrangement:

It is a pericyclic reaction that involves the redistribution of six electrons through the formation of a cyclic transition state from which a $\text{1,5-diene}$ gets converted into its isomeric form.

Example with mechanism of cope-arrangement:

In this mechanism, two pi-bonds and one sigma bond of the reactant molecule has been rearranged and formed two new pi-bonds through a cyclic transition state.

Identification of cope-rearrangement in a$1,5-diene$:

In the cope-rearrangement, the flow of electrons takes place between six bonds that are bonded as $\text{C=C-C-C-C=C}$. Identification of such a bonding pattern in a $\text{1,5-diene}$ indicates the possibility of Cope rearrangement to occur as shown here:

The carbon atoms that are involving in the cope-rearrangement are shown in bold.

Stereochemistry in a product formed:

• • In the product of a chemical reaction, if a carbon atom has been attached with four different carbon atoms, then it is known as chiral carbon atom or stereocenter in the product.
• • The bonds of the functional groups because of which a new chiral carbon is supposed to form have to be represented in solid wedge bond and hashed-wedge bonds according to the particular enantiomer.
• • Racemic mixture is the mixture of two enantiomers in equal proportions.
• • Enantiomers are non-superimposable mirror images.
• • Achiral product is the product in which there won’t be any chiral centre or stereocenter.