1. Which type of substituent group deactivates the benzene ring and directs electrophilic substitution to the meta position?

A. Electron donating groups like -OH B. Electron withdrawing groups like -NO2 C. Alkyl groups like methyl D. Halogens like chlorine

2. What is the expected positional isomer when a methyl group is already present on benzene?

A. Meta and para only B. Ortho and para only C. Ortho and meta only D. Para only

3. What is the main reason nitrobenzene reacts slower than benzene?

A. Nitro group is electron donating and activates the ring B. Nitro group is electron withdrawing and deactivates the ring C. Nitro group blocks incoming electrophiles physically D. Nitrobenzene is more aromatic

4. What is the main difference between alkylation and acylation of benzene?

A. Alkylation adds -COR groups, acylation adds alkyl groups B. Alkylation adds alkyl groups, acylation adds -COR groups C. Both add alkyl groups D. Both add acyl groups

5. Which of the following is NOT an effect of substituent groups on benzene reactivity?

A. Activating or deactivating the ring B. Directing further substitution to ortho, meta, or para positions C. Changing the ring from aromatic to aliphatic D. Affecting the speed of electrophilic substitution

6. What is the electrophile in the nitration of benzene?

A. NO3- B. NO2+ C. HNO3 D. SO3H+

7. What kind of reaction is Friedel-Crafts alkylation?

A. Electrophilic addition B. Free radical substitution C. Electrophilic aromatic substitution D. Nucleophilic aromatic substitution

8. What is the primary reason toluene reacts faster than benzene in electrophilic substitution reactions?

A. It has a stronger bond angle B. The methyl group is strongly electron withdrawing C. The methyl group donates electrons, activating the ring D. It has more double bonds than benzene

9. How is the benzene ring affected by a substituent like the methyl group (-CH3)?

A. It deactivates and directs meta substitution B. It has no effect on reactivity or orientation C. It activates the ring and directs ortho/para substitution D. It causes the ring to undergo addition reactions instead of substitution

10. Why does benzene preferentially undergo electrophilic substitution rather than addition reactions?

A. It is saturated and resistant to substitution B. Its double bonds are localized and reactive C. Its aromaticity and delocalized π electrons make it stable D. It contains no π electrons

11. Which substituent is classified as a strong activating ortho/para directing group?

A. -NO2 B. -NH2 C. -CN D. -Cl

12. What happens to the heat of hydrogenation of benzene compared to what would be expected if benzene had three isolated double bonds?

A. It is three times greater B. It is less than three times, indicating extra stability C. It is equal to the sum of three isolated double bonds D. It is zero because benzene cannot be hydrogenated

13. Which of the following is NOT a reason Kekule’s original structure failed to explain benzene’s properties?

A. It predicted multiple isomers for di-substituted benzene B. It failed to explain equal bond lengths in benzene C. It predicted benzene would undergo addition rather than substitution D. It stated benzene has no π electrons

14. Which reagent combination is typically used in Friedel-Crafts acylation reactions?

A. Alkyl chloride and AlCl3 B. Acyl chloride and AlCl3 C. Nitrobenzene and H2SO4 D. Br2 and FeBr3

15. What role does AlCl3 play in Friedel-Crafts alkylation of benzene?

A. Oxidizing agent B. Reducing agent C. Lewis acid catalyst D. Base catalyst

16. Which of the following is a weakly activating substituent on benzene?

A. -NH2 B. -OCH3 C. -CH3 D. -NO2

17. Why is benzene considered more stable than expected from Kekulé’s structure?

A. It has alternating single and double bonds B. It undergoes addition reactions easily C. It is a resonance hybrid with delocalized pi-electrons D. It has no double bonds

18. In Friedel-Crafts alkylation, what role does aluminum chloride (AlCl3) play?

A. It serves as a solvent B. It acts as a reducing agent C. It acts as a Lewis acid catalyst D. It is the source of alkyl groups

19. Why do halogens like F, Cl, Br, I deactivate benzene but direct substitution to ortho/para?

A. Due to their strong electron donation B. Due to a balance of inductive withdrawal and resonance donation C. Because they are positively charged D. Because they are non-polar

20. During Friedel-Crafts acylation, what is the nature of the electrophile generated?

A. Alkyl carbocation B. Acyl carbocation (acylium ion) C. Free radical D. Nucleophile

21. During sulphonation of benzene, which electrophilic species is primarily responsible for attacking the ring?

A. SO4- B. HSO3+ or SO3 C. SO2 D. H2SO4 itself

22. What electrophile is generated during the nitration of benzene?

A. NO+ B. NO2+ C. N2+ D. NO3+

23. Which reagent mixture is used to generate the nitronium ion (NO2+) in nitration?

A. HOCl and HNO3 B. H2SO4 and HNO3 C. HCl and HNO3 D. H2SO4 and SO3

24. In the mechanism of electrophilic aromatic substitution, what occurs after the formation of the sigma complex (arenium ion)?

A. Aromaticity is lost permanently B. The molecule immediately undergoes addition C. A proton (H+) is lost to restore aromaticity D. The ring breaks open

25. In sulphonation of benzene, what is the active electrophile?

A. SO3 B. HSO3+ C. H2SO4 D. SO4 2-

26. Which of the following groups deactivates the benzene ring but directs substitution to the ortho and para positions?

A. -NO2 B. -CN C. Halogens (F, Cl, Br, I) D. -NH2

27. Why do halogen substituents deactivate the benzene ring despite being ortho/para directing?

A. They have no inductive effect B. They withdraw electrons by induction but donate by resonance C. They strongly donate electrons through induction D. They prevent any substitution from occurring

28. Which group increases the electron density of the benzene ring, thus activating it?

A. -NO2 B. -CN C. -OH D. -SO3H

29. What rule does benzene’s aromaticity follow based on its pi-electron count?

A. Hund’s rule B. Pauli exclusion principle C. Huckel’s (4n + 2) rule D. Aufbau principle

30. The presence of how many π electrons satisfies Huckel’s rule for aromaticity?

A. 4n electrons B. 4n + 2 electrons C. 2n electrons D. 6n electrons

31. Which physical property of benzene is TRUE?

A. Benzene is a colorless liquid with a high melting point around 300°C B. Benzene mixes well with water C. Benzene burns with a smoky flame due to its unsaturation D. Benzene is odorless

32. Which reaction introduces a -SO3H group into benzene using fuming sulfuric acid?

A. Nitration B. Sulphonation C. Halogenation D. Alkylation

33. Which of the following groups is meta directing and deactivating in electrophilic substitution?

A. -OH B. -NO2 C. -CH3 D. -Br

34. Which group is deactivating but ortho/para directing due to its inductive and resonance effects?

A. -NO2 B. -Cl C. -OH D. -CH3

35. What type of bond overlap creates the delocalized pi system in benzene?

A. Sigma overlap of sp3 orbitals B. Lateral overlap of unhybridized p orbitals C. End-to-end overlap of s orbitals D. Ionic bonds within ring

36. Which of the following substituents is strongly electron withdrawing and meta directing?

A. -OH B. -NO2 C. -NH2 D. -CH3

37. What do the reagents Br2 and FeBr3 produce in halogenation of benzene?

A. Br radical B. Br+ electrophile C. FeBr2 D. Br- anion

38. Which substituent group is considered a strong activator and ortho/para-directing in electrophilic aromatic substitution?

A. -NO2 B. -OH C. -CN D. -COOH

39. What is required to restore aromaticity after electrophilic attack on benzene?

A. Addition of an electrophile B. Loss of a proton from sigma complex intermediate C. Gain of a proton D. Cleavage of carbon-carbon bond

40. Which electrophilic aromatic substitution uses a mixture of concentrated sulfuric acid and nitric acid?

A. Halogenation B. Nitration C. Sulphonation D. Friedel-Crafts alkylation

41. What happens in step two of electrophilic aromatic substitution?

A. Electrophile attacks benzene B. Aromatic ring breaks apart C. Loss of proton from intermediate restores aromaticity D. Electrons delocalize over ring

42. What is a phenyl group in benzene derivatives?

A. The benzene ring itself B. Benzene ring plus one hydrogen replaced by a substituent C. One hydrogen removed from benzene leaving C6H5 group D. Any substituted benzene derivative

43. Why does benzene generally undergo substitution reactions rather than addition reactions?

A. To increase its molecular weight B. Because addition reactions preserve aromatic stability C. Because addition reactions would destroy its aromaticity D. Because substitution is faster

44. What is the product when benzene undergoes halogenation using Br2 and FeBr3?

A. Bromobenzene B. Benzene bromide C. Benzyl bromide D. 1,2-dibromobenzene

45. What effect does a methyl group have on the reactivity of benzene in electrophilic substitution?

A. Deactivates and meta directing B. Deactivates and ortho/para directing C. Activates and meta directing D. Activates and ortho/para directing

46. What is the product when benzene reacts with acyl chloride in the presence of AlCl3?

A. Alkylbenzene B. Nitrobenzene C. Acylbenzene (ketone group attached) D. Chlorobenzene

47. The classic Kekulé structure failed to explain which property of benzene?

A. Its formula C6H6 B. Its planarity C. Its uniform bond lengths and unusual stability D. Its tendency to undergo addition reactions

48. Which type of hybridization is present in each carbon atom of benzene?

A. sp B. sp2 C. sp3 D. sp3d

49. What is the intermediate formed when the electrophile attacks benzene during electrophilic aromatic substitution?

A. Benzenonium ion B. Carbanion C. Radical cation D. Carbocation on side chain

50. Which catalyst is NOT typically used in Friedel-Crafts alkylation?

A. AlCl3 B. BF3 C. FeCl3 D. NaOH