Chapter D, Problem D.5P

Interpretation Introduction

Interpretation:

The approach of ${\text{OH}}^{\text{-}}$ on ${\text{CH}}_{\text{3}}\text{Cl}$ from the same end as $\text{Cl}$ in the ${\text{S}}_{\text{N}}\text{2}$ step between ${\text{OH}}^{\text{-}}$ and ${\text{CH}}_{\text{3}}\text{Cl}$ is to be discussed.

Concept introduction:

In bimolecular nucleophilic substitution reactions (${\text{S}}_{\text{N}}\text{2}$), a substrate undergoes substitution in which the leaving group is replaced by the nucleophile. The conjugate bases of strong acids act as nucleophiles. The negative charged nucleophile is attracted to an atom bearing a positive charge on the electrophile. The atom with negative charge on the nucleophile forms a bond with the substrate, and in the same step, the bond will break between the carbon and the leaving group. In an elementary step, the flow of electron tends from the electron rich group to an electron poor atom. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) must have axial overlap or parallel overlap. The axial overlap between HOMO and LUMO has substantial net overlap, so this reaction is allowed. If the HOMO and LUMO do not have a substantial overlap, this overlap is forbidden.