Chapter 8, Problem 8.74P

Interpretation Introduction

Interpretation:

Whether the product formed in the given reaction under conditions that favor ${\text{S}}_{\text{N}}\text{1}$ reaction will be a mixture of stereoisomers is to be determined.

Concept introduction:

An ${\text{S}}_{\text{N}}\text{1}$ reaction involves a two-step mechanism. The leaving group breaks off from the substrate along with its bond pair of electrons to form a carbocation. The carbon atom to which the leaving group was bonded is left with an incomplete octet and a full positive charge.

The carbocation is a charged unstable specie and is subject to a rearrangement if a $\text{1, 2-hydride}$ or a $\text{1, 2-methyl}$ shift results in a more stable carbocation.

The hybridization of the carbon also changes from tetrahedral ${\text{sp}}^3$ to planar ${\text{sp}}^2$. The incoming nucleophile can then approach the carbocation from above the plane or below the plane, with equal probability unless another group nearby restricts approach from one direction. If the reaction center is a stereoisomer, then this results in formation of a mixture of stereoisomers.