Chapter 7.3, Problem 7CC

Interpretation Introduction

Interpretation:

The possible mechanism should be drawn and identified for the given alkylated molecule of melphalan.

Concept Introduction:

Leaving group: It is a fragment that leaves the chemical compound with pair of electrons in a heterolytic bond cleavage. The ${\text{S}}_{\text{N}}2$ reactivity increases in molecule with better leaving group.

Nucleophile: Donates pair of electrons to positively charged substrate resulting in the formation of chemical bond.

Structure of the substrate plays major role in the reactivity of ${\text{S}}_{\text{N}}2$ reaction. If the substrate is more substituted then the rate of the reaction will becomes slower. Since the mechanism of ${\text{S}}_{\text{N}}2$ reaction proceeds through backside attack on the substrate, it depends on steric factor that if more groups attached near the leaving group the reactivity becomes slower. The ${\text{S}}_{\text{N}}2$ reactivity increases in molecule with better leaving group. The reactivity increases in the order as follows,

Elimination Reaction: It is just reverse reaction of addition where substituent from the given molecule is removed via E1 (the reaction depends only on the substrate involved in the reaction) or E2 (the reaction depends on both of the substituents in the reaction) mechanism.