Aromatic hydrocarbons benzene structure aromaticity and electrophilic substitution - One Line Questions

1. Which of the following groups is a deactivating and meta-directing group in electrophilic aromatic substitution? — -CHO
2. Which of the following groups is an activating and ortho, para-directing group in electrophilic aromatic substitution? — -OH
3. Which of the following is a deactivating group due to resonance effect? — -NO2
4. The resonance energy of benzene is approximately: — 72 kJ/mol
5. The compound cyclopentadienyl anion is aromatic because it has: — 6 pi electrons
6. The Kekulé structure of benzene proposes: — A planar hexagonal ring with two resonance structures showing alternating single and double bonds
7. Hückel's rule states that for a compound to be aromatic, it must possess a planar ring system with (4n+2) pi electrons, where 'n' is: — A non-negative integer
8. Which of the following is a correct representation of a resonance structure of benzene? — Two structures with alternating single and double bonds that are equivalent
9. The presence of an electron-withdrawing group on the benzene ring generally: — Deactivates the ring and directs meta
10. The energy released when two moles of H2 are added to benzene to form cyclohexane is called: — Heat of hydrogenation
11. Which type of reaction is favored by aromatic hydrocarbons due to their stable delocalized pi electron system? — Substitution reactions
12. The Friedel-Crafts alkylation of benzene requires: — An alkyl halide and a Lewis acid catalyst
13. Which of the following is a requirement for a compound to be considered aromatic according to Hückel's rule? — A planar ring system with a delocalized (4n+2) pi electron cloud
14. The mechanism of electrophilic substitution in benzene involves: — Attack by an electrophile to form a sigma complex, followed by loss of a proton
15. Which of the following is NOT an aromatic compound? — Cyclohexane
16. What is the electrophile in the bromination of benzene using Br2 and FeBr3? — Br+
17. What is the molecular formula of benzene? — C6H6
18. The intermediate formed during the electrophilic substitution of benzene is known as: —
19. What is the product of the reaction of benzene with CH3Cl in the presence of AlCl3? — Toluene
20. The term 'aromatic' originally referred to: — Compounds with a strong odor
21. The presence of an electron-donating group on the benzene ring generally: — Activates the ring and directs ortho, para
22. In the electrophilic substitution of toluene, the methyl group is: — Activating and ortho, para-directing
23. The structure of benzene was proposed by: — August Kekulé
24. In electrophilic substitution of benzene, the attacking species is an: — Electron-deficient species
25. Which of the following reactions is characteristic of aromatic hydrocarbons like benzene? — Electrophilic substitution
26. Which of the following is an example of an aromatic hydrocarbon? — Benzene
27. The electrophilic substitution reaction that introduces an acyl group (-COR) onto the benzene ring is called: — Friedel-Crafts acylation
28. Which of the following is a common Lewis acid catalyst used in Friedel-Crafts reactions? — AlCl3
29. The reaction where benzene reacts with a halogen in the presence of a Lewis acid catalyst is called: — Aromatic halogenation
30. The relative ease of electrophilic substitution of benzene compared to addition to alkenes is explained by: — Loss of aromaticity during addition
31. The resonance structures of benzene contribute to its: — Delocalized electron cloud and stability
32. The product of the Friedel-Crafts alkylation of benzene with ethyl chloride and AlCl3 can undergo: — All of the above
33. Which of the following is a consequence of the aromaticity of benzene? — It reacts via electrophilic substitution rather than addition
34. The stability of benzene is attributed to: — Resonance and delocalization of pi electrons
35. The order of reactivity of benzene towards different electrophilic substitution reactions is generally: — Friedel-Crafts > Halogenation > Nitration > Sulfonation
36. Which of the following is a common electrophile used in the nitration of benzene? — NO2+
37. What is the electrophile generated in the Friedel-Crafts acylation of benzene? — R-C=O+
38. Which reaction is used to convert benzene to nitrobenzene? — Reaction with HNO3 and H2SO4
39. The bond length between carbon atoms in benzene is: — Intermediate between a C-C single bond and a C=C double bond
40. In the sulfonation of benzene, the electrophile is: — SO3
41. What is the hybridization of each carbon atom in the benzene ring? — sp2
42. What is the limiting factor for the number of pi electrons in Hückel's rule for aromaticity? — The total number of pi electrons must be 4n+2
43. The loss of a proton from the arenium ion in electrophilic substitution of benzene restores: — Both B and C
44. Aromaticity in benzene is due to: — The cyclic arrangement of sp2 hybridized carbons with a delocalized pi system of 6 electrons
45. Carbocation rearrangements can occur during Friedel-Crafts alkylation due to: — The tendency of carbocations to rearrange to more stable forms
46. What is the role of concentrated sulfuric acid in the nitration of benzene using nitric acid? — To provide the electrophile (NO2+)
47. Which of the following is an example of a non-benzenoid aromatic compound? — Cyclopentadienyl anion
48. The delocalization of pi electrons in benzene is often represented by: — A circle inside a hexagon
49. Which of the following is a characteristic of aromatic compounds? — Contain a delocalized pi electron system
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