MCQs on Aromaticity

Aromatic hydrocarbons are also known as arenes. They may or may not contain a benzene ring. Earlier aromatic compounds are named so due to their distinct aroma but now any compound satisfying Hรผckel’s Rule of aromaticity is considered aromatic. Any compound with a planar ring structure with delocalised ๐žน electrons and a number of ๐žน electrons is equal to (4n+2)๐žน is aromatic. Where n is an integer (0, 1, 2, etc.). E.g. benzene, naphthalene, anthracene, cyclopentadienyl anion, cycloheptatrienyl cation, etc.

1. Which of the following compounds is not aromatic?

Aromaticity-1

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

(a) Delocalisation of ๐žน-electrons

(b) Resonance

(c) Greater stability

(d) Electrophilic additions

3. Which of the following statements is true for benzene?

(a) Benzene easily undergoes addition due to unsaturation

(b) ๐žน-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

4. Which of the following is the correct representation to relate the two resonating Kekule structures of benzene?

(a) โ†’

(b) โ‰ก

(c) โ†”

(d) โ‡Œ

5. The bond length of C-C bonds in benzene is

(a) 110 pm

(b) 156 pm

(c) 121 pm

(d) 139 pm

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

(a) Cyclic

(b) Planar

(c) (4n+2)๐žน electrons

(d) All of the above

7. Which of the following is incorrect for benzene?

(a) Planar C6 ring

(b) Localised ๐žน bonding

(c) sp2 hybridised C atoms

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

8. 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

9. The number of delocalised ๐žน electrons in the benzene ring are

(a) 6

(b) 8

(c) 2

(d) 4

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

(a) NO2+

(b) NO2

(c) NO3

(d) HNO3

Answer

1. (c)

2. (d)

3. (b)

4. (c)

5. (d)

6. (d)

7. (d)

8. (b)

9. (a)

10. (a)

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