Chapter 17, Problem 74CP

(a)

Interpretation Introduction

Interpretation:

Plausible mechanism for the formation of compound A has to be drawn.

Concept Introduction:

${\text{S}}_{\text{N}}2$Reaction: It is a nucleophilic substitution reaction in which the rate determining step depends on both of the molecules involved. The bond making and the bond breaking process happens simultaneously in this reaction.

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.

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

Deprotonation: The reaction in which proton is removed from the compound using reagents is known as deprotonation.

(b)

Interpretation Introduction

Interpretation:

Structure of compound B and plausible mechanism for the formation of compound B has to be given.

Concept Introduction:

${\text{S}}_{\text{N}}2$Reaction: It is a nucleophilic substitution reaction in which the rate determining step depends on both of the molecules involved. The bond making and the bond breaking process happens simultaneously in this reaction.

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.

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

Deprotonation: The reaction in which proton is removed from the compound using reagents is known as deprotonation.

(c)

Interpretation Introduction

Interpretation:

Reason for why compound B is favored over compound A has to be given.

Concept Introduction:

Huckel’s rule states that based on the number of pi electrons planar, monocyclic, and conjugated polyene compounds can be classified as aromatic or anti-aromatic.

1. a) The number of $\pi$ electrons in a cyclic conjugated system is $4n$ where n is an integer, then it is antiaromatic.
2. b) The number of $\pi$ electrons in a cyclic conjugated system is $\left(4n+2\right)$ where n is an integer, then it is aromatic.

Aromatic compounds are more stable than non-aromatic compound

Compounds having $\left(4n+\pi \right)$ electrons are aromatic systems that exhibit stabilization associated with aromaticity whereas $4n$ electron system exhibits antiaromatic destabilization.