Chapter 16, Problem 79CP

(a)

Interpretation Introduction

Interpretation:

The structure of the compound 2 has to be determined and the explanation for its formation as racemic mixture has to be given.

Concept introduction:

There are mainly three types of pericyclic reactions,

1. 1. Electrocyclic reactions
2. 2. Cycloaddition reactions
3. 3. Sigmatropic reactions

In an electrocyclic reaction “one new sigma- bond is formed or broken.”

  

  $\begin{array}{ccc}\begin{array}{l}\text{Electron}\\ \text{system}\end{array}& \text{Heat}& \text{hυ}\\ \text{4π}& \text{Con}& \text{Dis}\\ \text{6π}& \text{Dis}& \text{Con}\end{array}$

If the two orbitals rotate in same direction, then it is called as con rotation and if it is in opposite direction, then it is called dis rotation.

(b)

Interpretation Introduction

Interpretation:

The mechanism for the conversion of compound 2 to endiandric acid G has to be determined.

Concept introduction:

There are mainly three types of pericyclic reactions,

1. 1. Electrocyclic reactions
2. 2. Cycloaddition reactions
3. 3. Sigmatropic reactions

In an electrocyclic reaction “one new sigma- bond is formed or broken.”

  

  $\begin{array}{ccc}\begin{array}{l}\text{Electron}\\ \text{system}\end{array}& \text{Heat}& \text{hυ}\\ \text{4π}& \text{Con}& \text{Dis}\\ \text{6π}& \text{Dis}& \text{Con}\end{array}$

If the two orbitals rotate in same direction, then it is called as con rotation and if it is in opposite direction, then it is called dis rotation.

(c)

Interpretation Introduction

Interpretation:

The structure of endiandric acid C and the mechanism for its formation has to be determined.

Concept introduction:

• Cycloaddition reaction is a concerted addition reaction of two reactants to form a ring; in which two π-bonds are converted to two σ-bonds.
• Diels-Alder reaction is a $\left[\text{4+2}\right]\text{ cycloaddition}$ reaction between a diene and a dienophile and produces cyclohexene as a product.