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 HΓΌckel’s Rule of aromaticity is considered aromatic. Any compound with a planar ring structure with delocalised πΉ electrons and a number of πΉ electrons is equal to (4n+2)πΉ 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?
2. Which of the following is not a characteristic property of arenes?
(a) Delocalisation of πΉ-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) πΉ-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) β
(b) β‘
(c) β
(d) β
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)πΉ electrons
(d) All of the above
7. Which of the following is incorrect for benzene?
(a) Planar C6 ring
(b) Localised πΉ 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 πΉ 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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