Aromaticity MCQs

Aromatic hydrocarbons, also known as arenes, may or may not include a benzene ring. Historically, they were named for their distinctive aroma, but today, a compound is classified as aromatic if it adheres to Hückel’s Rule of aromaticity. According to this rule, a compound is aromatic if it has a planar ring structure with delocalized π electrons and a number of π electrons equal to (4n+2)π, where n is a non-negative integer (0, 1, 2, etc.). Examples include benzene, naphthalene, anthracene, the cyclopentadienyl anion, and the cycloheptatrienyl cation.

Which of the following statements is true for benzene?

(a) Benzene easily undergoes addition due to unsaturation
(b) π-electrons are delocalised in the benzene ring
(c) Three isomeric forms are formed on monosubstitution of benzene
(d) Two types of C-C bonds are present in benzene

(b) π-electrons are delocalised in the benzene ring

Which of the following is the reactive species in the nitration of benzene?

(a) NO2+
(b) NO2–
(c) NO3
(d) HNO3

(a) NO2+

The bond length of C-C bonds in benzene is

(a) 110 pm
(b) 156 pm
(c) 121 pm
(d) 139 pm

(d) 139 pm

Which of the following is not a characteristic property of arenes?

(a) Delocalisation of π-electrons
(b) Resonance
(c) Greater stability
(d) Electrophilic additions

(d) Electrophilic additions

Which of the following is the correct representation to relate the two resonating Kekulé structures of benzene?

(a) →
(b) ≡
(c) ↔
(d) ⇌

(c) ↔

Which of the following is a characteristic of an aromatic compound?

(a) Cyclic
(b) Planar
(c) (4n+2) π electrons
(d) All of the above

(d) All of the above

Which of the following is incorrect for electrophilic substitution?

(a) -NO2 is deactivating and m-directing
(b) -Cl is activating and o, p-directing
(c) -OH is activating and o, p-directing
(d) -CH3 is activating and o, p-directing

(b) -Cl is activating and o, p-directing

The number of delocalised π electrons in the benzene ring is

(a) 6
(b) 8
(c) 2
(d) 4

(a) 6

Which of the following is incorrect for benzene?

(a) Planar C6 ring
(b) Localised π bonding
(c) sp2 hybridised C atoms
(d) It shows reactions characteristics of C=C double bonds

(d) It shows reactions characteristics of C=C double bonds

1. Which of the following compounds is not aromatic?

Aromaticity-1

C