Chapter 28, Problem 28.53AP

Interpretation Introduction

(a)

Interpretation:

Anticipating the isolation of the potentially aromatic hydrocarbon B, a group of chemists irradiated compound A with ultraviolet light. Compound C was obtained as a product instead of B.

The reason for compound B might be expected to be unstable in spite of its cyclic array of 4n+2 π electrons is to be stated.

Concept introduction:

The stability of aromatic compounds is high due to their stabilization energy. In order to retain their aromaticity (resultant stabilization energy) aromatic compounds undergo substitution reaction more readily. Aromaticity in compounds is considered only the system having 4n+2 π electrons, planar, cyclic, and should have conjugated π-electrons.

Interpretation Introduction

(b)

Interpretation:

The formation of compound B is allowed by the pericyclic selection rules is to be explained.

Concept introduction:

Pericyclic reactions deal with electrons shift in a concerted manner. Moreover, in these reactions the breaking of reactant bonds and the formation of product bonds are formed at the same time.i.e., without the formation of intermediates. The word ‘pericyclic’ means around the cycle. Notably, the pericyclic reactions are classified as electrocyclic, cycloaddition and sigmatropic reactions based on the activation of reaction, the number of electrons involved and the stereochemistry outcome of the reactions. The selection rules of pericyclic reaction deal mostly on the rates of reaction and does not tell anything about position of equilibrium and equilibrium constant values.

Interpretation Introduction

(c)

Interpretation:

The formation of the observed product C is to be explained.

Concept introduction:

Pericyclic reactions deal with electrons shift in a concerted manner. Moreover, in these reactions the breaking of reactant bonds and the formation of product bonds are formed at the same time.i.e., without the formation of intermediates. The selection rules of pericyclic reaction deal mostly on the rates of reaction and does not tell anything about position of equilibrium and equilibrium constant values.