Chapter 11, Problem 49P

Interpretation Introduction

Interpretation:

The mechanism for the formation of chiral glycol from 1,2-chlorhydrin including formal charges and movement of electrons is to be proposed.

Concept introduction:

Substitution reaction: A reaction in which one of the hydrogen atoms of a hydrocarbon, or a functional group, is substituted by any other functional group is called substitution reaction.

Elimination reaction: A reaction in which two substituent groups are detached and a double bond is formed is called elimination reaction.

Addition reaction: It is the reaction in which unsaturated bonds are converted to saturated bonds by addition of molecules.

Nucleophilic substitution happens by two different mechanisms: ${\text{S}}_{\text{N}}1$ and ${\text{S}}_{\text{N}}\text{2}$

The ${\text{S}}_{\text{N}}1$ reaction is unimolecular nucleophilic substitution reaction, which means only one component is involved in the rate determining step.

In the rate determining step, leaving group generates a carbocation intermediate.

Carbocation intermediated then undergoes a rapid reaction with nucleophile.

Forms a racemic mixture.

The ${\text{S}}_{\text{N}}\text{2}$ reaction is bimolecular nucleophilic substitution reaction, which means two components are involved in the rate determining step.

In the rate determining step, nucleophile approaches the carbon from the side directly opposite to the leaving group.

The ${\text{S}}_{\text{N}}\text{2}$ reaction is a concerted reaction as bond formation and bond breaking occurs in the same step.

This back side attack of nucleophile leads to inversion of configuration.