Chapter 9, Problem 9.41P

Interpretation Introduction

Interpretation:

It is to be determined whether the given overall reaction occurs by ${\text{S}}_{\text{N}}{\text{2, S}}_{\text{N}}\text{1, E2, or E1}$ mechanism, and complete and detailed mechanism for the given reaction is to be drawn.

Concept introduction:

In the given reaction, the good leaving group bromine (Br) is attached to tertiary carbon atom and there is also presence of polar protic solvent. Also, the products of the given reaction are enantiomers, indicating that the racemic mixture is formed. All these factors suggest that the reaction should follow ${\text{S}}_{\text{N}}\text{1}$ mechanism. The ${\text{S}}_{\text{N}}\text{1}$ reaction is unimolecular nucleophilic substitution reaction where the rate determining step is the formation of a stable carbocation. In the second step, the nucleophile attacks the carbocation to yield a racemic mixture.

The carbocation intermediate formed in ${\text{S}}_{\text{N}}\text{1}$ reaction is ${\text{sp}}^{\text{2}}$ hybridized, and its molecular geometry is trigonal planar. The given geometry allows two different points of nucleophilic attack. The formation of the stereoisomer depends on the stereochemical nature of the given reactant.