Chapter 18, Problem 95CP

(a)

Interpretation Introduction

Interpretation:

Mechanism for the conversion of 1 into 3 has to be proposed.

Concept introduction:

Electrophilic aromatic substitution reaction: It is a substitution reaction occurs on an aromatic ring where an atom present on it is displaced by an electrophile.

Resonance is an electron displacement effect for stabilizing a molecule through delocalization of bonding electrons in the pi orbital.

Delocalized electrons stabilize a compound. The extra stability gains from having delocalized electrons are called resonance stabilization or resonance energy.

According to the explanations by Lewis acid theory, if a species donates an electron pair then it is a Lewis base whereas if a species receives an electron pair, then it is Lewis acid.

When acid and base reacts, a new bond is formed between them by the lone pair of electrons.

(b)

Interpretation Introduction

Interpretation:

Six rings in compound 3 are whether aromatic, providing an extended aromatic ring has to be explained.

Concept introduction:

The conditions for aromatic compound are,

• It should be cyclic
• It should be planar (all atoms in the same plane)
• It must obey the Huckel’s rule (have $\left(4n+2\right)\pi$ electrons.)
• It must be conjugated $\text{π}$ system(all carbon should be in ${\text{sp}}^{\text{2}}$ hybridized state)

Hybridization is the mixing of valence atomic orbitals to get equivalent hybridized orbitals that having similar characteristics and energy.

(c)

Interpretation Introduction

Interpretation:

Reason for why the two central rings of compound 3 are slightly twisted has to be explained.

Concept introduction:

The conditions for aromatic compound are,

• It should be cyclic
• It should be planar (all atoms in the same plane)
• It must obey the Huckel’s rule (have $\left(4n+2\right)\pi$ electrons.)
• It must be conjugated $\text{π}$ system(all carbon should be in ${\text{sp}}^{\text{2}}$ hybridized state)

Steric hindrance is the crowding in a molecule due to the presence of bulky substituent.