Chapter 18, Problem 93CP

(a)

Interpretation Introduction

Interpretation: Mechanism for the formation of compound A and B has to be proposed.

Concept Introduction:

Electrophilic substitution reaction is a type of reaction in which a particular group or atom in a compound is replaced by electrophile.

Electrophile: It is positively charged species which seeks for negative charge and hence accepts pair of electrons from negatively charged species (Nucleophiles) which results in the formation of chemical bond.

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.

(b)

Interpretation Introduction

Interpretation: Reason for why formation of compound A is favored over formation of compound B has to be determined.

Concept Introduction:

• Electrophilic substitution reaction is a type of reaction in which a particular group or atom in a compound is replaced by electrophile. An electrophile is a species that is deficient of electrons
• Deactivators are electron withdrawing groups attached to the benzenes that have either positive charge or an atom with high electronegativity. They are meta directors.
• Benzene is an electron rich aromatic compound and undergoes electrophilic substitution reactions.
• The position that the electrophile occupies in the ring system depends on various factors like – presence of substituents, activation and deactivation of the ring etc.
• The pi electrons of the aromatic system must be available freely for the reaction to occur. Further, the aromatic ring must not have many bulk substituents on it to ease the any type of electrophilic substitution reaction. Presence of many bulk substituents hinders the ability of the delocalizing pi electrons to bond with the electrophile
• Activators are electron donating groups attached to the benzenes that have either electron density that is able to push into benzene ring or a lone pair of electrons. They are ortho–para directing.