Chapter 14.10, Problem 21ATS

Interpretation Introduction

Interpretation: The mechanism has to be explained.

Concept Introduction:

The reactions of Epoxides with strong nucleophiles requires a strong driving force that helps in the removal of ring strain associated with the three-memebered ring of an Epoxide. These ring opening reactions also occur under acidic conditions.

The mechanism of acid-catalyzed ring opening of an Epoxide occurs in two steps.

In first step, the protonation of Epoxide occurs.

In second step, the attack of nucleophile occurs in the protonated Epoxide by ${\text{S}}_{\text{N}}\text{2}$ process.

The important features of ring opening reactions are regiochemistry and stereochemistry.

1. 1) Regiochemistry: The regiochemistry depends on the nature of Epoxide when the starting Epoxide is unsymmetrical.
2. 2) Stereochemistry: Inversion of configuration is observed when nucleophilic attack is seen at less hindered primary position if one position is primary and other is secondary. This steric effect is also expected from ${\text{S}}_{\text{N}}\text{2}$ process.