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 Hückel’s Rule of aromaticity is considered aromatic. Any compound with a planar ring structure with delocalised 𝞹 electrons and a number of 𝞹 electrons is equal to (4n+2)𝞹 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 𝞹-electrons
(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) 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
4. Which of the following is the correct representation to relate the two resonating Kekule structures of benzene?
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?
(c) (4n+2)𝞹 electrons
(d) All of the above
7. 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
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 𝞹 electrons in the benzene ring are
10. Which of the following is the reactive species in the nitration of benzene?