Chapter 22, Problem 22.9P

Interpretation Introduction

Interpretation:

How to synthesize $\text{2-phenylbut-2-ene}$ from benzene is to be shown.

Concept introduction:

When benzene is treated with an alkyl halide in the presence of the Lewis acid (e.g., ${\text{AlCl}}_{\text{3}}$) as a catalyst, alkylation takes place at the benzene ring; it is known as a Friedel-Crafts alkylation reaction. A Friedel-Crafts alkylation reaction does not occur readily when the halogen atom of the alkyl halide is bonded to an ${\text{sp}}^{\text{2}}$ hybridized carbon. A Friedel-Crafts alkylation reaction is also susceptible to carbocation rearrangements. An organometallic compound has a polar covalent $\text{C-M}$ bond. For example, the Grignard reagent ($\text{RMgX}$) has a polar R-Mg bond; an alkyllithium ($\text{RLi}$) has a polar covalent $\text{C-Li}$ bond. Since carbon is bonded with an electropositive element, carbon possesses the partial negative charge and acts as the nucleophile as well as the base. Thus it is used for the new $\text{C-C}$ bond formation with electrophilic carbon. The nucleophilic part (${\text{R}}^{\text{-}}$) of the Grignard reagent shows a nucleophilic addition reaction with electrophilic carbon of the carbonyl compounds.