Aromatic Compounds and Electrophilic Substitution focuses on the unique stability, structure, and reactivity of aromatic systems, particularly benzene and its derivatives. This chapter is a cornerstone of Class 11–12 Organic Chemistry, undergraduate studies, and competitive examinations, emphasizing structure–reactivity relationships and reaction mechanisms.
In this section, you will study:
Concept of aromaticity – Hückel’s rule, cyclic conjugation, and planarity
Structure of benzene – resonance, molecular orbital picture, and stability
Aromatic vs anti-aromatic vs non-aromatic compounds
Orientation and reactivity effects of substituents
Activating vs deactivating groups
Ortho/para vs meta directing effects
Comparative reactivity of benzene and substituted benzenes
Limitations and rearrangements in Friedel–Crafts reactions
Polycyclic aromatic hydrocarbons (introductory)
Distinguishing features of aromatic substitution vs addition reactions
NCERT- and UG-aligned explanations, with reaction mechanisms, diagrams, tables, MCQs, and PYQs
The content is structured to develop mechanistic understanding, improve prediction of reaction outcomes, and strengthen analytical thinking, all essential for board exams, NEET, JEE, CUET-UG, and undergraduate evaluations.
Mastering Aromatic Compounds and Electrophilic Substitution is key to understanding advanced organic chemistry, pharmaceuticals, dyes, polymers, and industrial synthesis routes.
Q. In the Friedel-Crafts alkylation of benzene, which of the following is a potential problem?
A.
Polyalkylation
B.
Dealkylation
C.
Hydrogenation
D.
Oxidation
Solution
Polyalkylation can occur in Friedel-Crafts alkylation, leading to multiple alkyl groups being added to the benzene ring.
Q. What is the product of the Friedel-Crafts acylation of benzene with acetyl chloride (CH3COCl) in the presence of AlCl3?
A.
Acetophenone
B.
Benzophenone
C.
Benzyl acetate
D.
Phenyl acetate
Solution
The product of the Friedel-Crafts acylation of benzene with acetyl chloride is acetophenone, formed by the introduction of the acetyl group onto the benzene ring.
Q. What is the stereochemical outcome of the electrophilic substitution of 1,2-dimethylbenzene (o-xylene) at the 4-position?
A.
Only one product is formed.
B.
Two products are formed, one being a racemic mixture.
C.
Only one enantiomer is formed.
D.
No reaction occurs.
Solution
Only one product is formed when 1,2-dimethylbenzene is substituted at the 4-position, as the two methyl groups are in positions that do not create stereoisomers.
Q. Which of the following compounds is least reactive towards electrophilic substitution?
A.
Benzene
B.
Toluene
C.
Nitrobenzene
D.
Anisole
Solution
Nitrobenzene is least reactive towards electrophilic substitution due to the strong electron-withdrawing effect of the nitro group, which deactivates the ring.
