Unit 9: Aromatic Hydrocarbons

What are Aromatic Hydrocarbons?

Aromatic Hydrocarbons are organic compounds characterized by the presence of one or more aromatic rings, which are stable ring structures with alternating double bonds. This unit explores the structure, properties, and reactions of aromatic hydrocarbons, including benzene and its derivatives. Students will study the unique characteristics of these compounds, their behavior in chemical reactions, and their significance in various industrial and chemical applications.

Key Topics in Aromatic Hydrocarbons:

• Benzene Structure: Understanding the structure of benzene, the simplest aromatic hydrocarbon, including its ring formation and resonance stabilization.
• Aromaticity: Examining the concept of aromaticity and the criteria that define aromatic compounds, such as Huckel’s rule.
• Derivatives of Benzene: Exploring the various functional groups attached to the benzene ring, including toluene, phenol, and aniline, and their chemical properties.
• Reactions of Aromatic Hydrocarbons: Studying the typical reactions of aromatic hydrocarbons, including electrophilic aromatic substitution, nitration, and sulfonation.
• Applications: Learning about the practical uses of aromatic hydrocarbons in pharmaceuticals, dyes, and synthetic materials.

Benefits of Studying Aromatic Hydrocarbons:

• In-Depth Understanding: Provides insights into the unique properties and behaviors of aromatic compounds, essential for advanced organic chemistry.
• Chemical Insight: Enhances comprehension of how aromatic hydrocarbons participate in various chemical reactions and their role in different industries.
• Preparation for Advanced Topics: Equips students with foundational knowledge for studying more complex organic chemistry topics and applications.

This unit is crucial for understanding the special characteristics and applications of aromatic hydrocarbons, offering essential knowledge for further studies in organic chemistry and practical applications.

1. The benzene molecule contains

a. Three double bonds
b. Two double bonds
c. One double bonds
d. Delocalized pi electron cloud

2. Aromatic hydrocarbons are the derivatives of

a. Normal series of paraffins
b. Alkenes
c. Benzene
d. Cyclohexane

3. Which of the following acid can be used as a catalyst in Friedel-Crafts
reactions?

a. AlCl₃
b. HNO₃
c. BeCl₂
d. NaCl

4. Benzene cannot undergo

a. Substitution reactions
b. Addition reactions
c. Oxidation reactions
d. Elimination reactions

5. Amongst the following, the compound that can be most readily
sulphonated is

a. Toulene
b. Benzene
c. Nitrobenzene
d. Chlorobenzene

6. During nitration of benzene, the active nitrating agent is

a. NO₃
b. NO_2⁺
c. NO₂
d. HNO₃

7. Which compound is the most reactive one:

a. Benzene
b. Ethene
c. Ethane
d. Ethyne

8. The electrophile in aromatic sulphonation is:

a. H₂SO₄
b. HSO₄^–
c. SO₃
d. SO_3⁺

9. Aromatic compounds burn with sooty flame because:

a. They have high percentage of hydrogen
b. They have a ring structure
c. They have high percentage of carbon
d. They resist reaction with air

10. The conversion of n-hexane into benzene by heating in the presence of Pt
is called:

a. Isomerization
b. Aromatization
c. Dealkylation
d. Rearrangement