Unit 9: Aromatic Hydrocarbons

11. Aromatic hydrocarbons are characterized by:

a) Straight-chain structures
b) Benzene rings with alternating double bonds
c) Single bonds only
d) Triple bonds between carbon atoms
Answer: b) Benzene rings with alternating double bonds

12. The simplest aromatic hydrocarbon is:

a) Toluene
b) Benzene
c) Xylene
d) Phenol
Answer: b) Benzene

13. Benzene has the molecular formula:

a) C₆H₆
b) C₆H₁₂
c) C₇H₈
d) C₆H₄
Answer: a) C₆H₆

14. The concept of “resonance” in benzene describes:

a) The existence of multiple structures contributing to the hybrid
b) The presence of single bonds only
c) The presence of triple bonds
d) The uniform distribution of electron density in a ring
Answer: a) The existence of multiple structures contributing to the hybrid

15. Which of the following is an example of a substituted aromatic hydrocarbon?

a) Methane
b) Ethylene
c) Toluene
d) Ethanol
Answer: c) Toluene

16. In the nitration of benzene, the electrophile involved is:

a) NO₂⁺
b) Cl⁺
c) Br₂
d) H⁺
Answer: a) NO₂⁺

17. The reaction of benzene with sulfuric acid and sulfur dioxide is known as:

a) Friedel-Crafts alkylation
b) Friedel-Crafts acylation
c) Nitration
d) Sulfonation
Answer: d) Sulfonation

18. The product of the Friedel-Crafts alkylation of benzene with ethyl chloride is:

a) Toluene
b) Ethylbenzene
c) Xylene
d) Benzyl alcohol
Answer: b) Ethylbenzene

19. Which reagent is used in the Friedel-Crafts acylation of benzene?

a) AlCl₃
b) H₂SO₄
c) HNO₃
d) HCl
Answer: a) AlCl₃

20. In an aromatic ring, the term “ortho” refers to:

a) The position of substituents 1,2-positions on the ring
b) The position of substituents 1,3-positions on the ring
c) The position of substituents 1,4-positions on the ring
d) The position of substituents 1,5-positions on the ring
Answer: a) The position of substituents 1,2-positions on the ring