Thermodynamics. Akpomie

Question 1

22. Which of the following compounds is a good example of a heterocyclic aromatic compounds?a) Pyridineb) Furanc) Thiophened) All of the above

Answer 1

Answer: d) All of the aboveExplanation: All three compounds are heterocyclic aromatic compounds. They contain atleast one heteroatom (nitrogen

Question 2

23. What is the name of the reaction used to convert aniline to benzene?a) Friedel-Crafts alkylationb) Reductionc) Oxidationd) Halogenation

Answer 2

Answer: c) OxidationExplanation: Aniline can be oxidized to benzene using strong oxidizing agents like potassium permanganate (KMnO4) or chromic acid (H2CrO4).

Question 3

24. Which of the following statements is TRUE about the reactivity of benzene compared to cyclohexane?a) Benzene is more reactive than cyclohexane.b) Benzene is less reactive than cyclohexane.c) Benzene and cyclohexane have similar reactivity.d) The reactivity depends on the specific reaction conditions.

Answer 3

Answer: b) Benzene is less reactive than cyclohexane.Explanation: Benzene’s aromaticity makes it less susceptible to typical alkane reactions like addition reactions. It prefers electrophilic aromatic substitution reactions

Question 4

25. What is the primary reason for the lower reactivity of aromatic hydrocarbons compared to alkenes?a) The presence of pi electrons in the ring system.b) The lack of pi electrons in the ring system.c) The greater stability of aromatic compounds due to resonance.d) The weaker bond strength in aromatic compounds.

Answer 4

Answer: c) The greater stability of aromatic compounds due to resonance.Explanation: Aromatic compounds gain stability from resonance delocalization of their pi electrons. This makes them less reactive than alkenes

Question 5

26. Which of the following statements is TRUE about the resonance structures of benzene?a) They are all equally stable.b) They are all equally unstable.c) The actual structure of benzene is a hybrid of the resonance structures.d) The actual structure of benzene is one specific resonance structure.

Answer 5

Answer: c) The actual structure of benzene is a hybrid of the resonance structures.Explanation: Benzene’s actual structure is a hybrid of the two major resonance structures

Question 6

27. Which of the following statements is TRUE about the electrophilic aromatic substitution reaction?a) It always proceeds through a carbocation intermediate.b) It always proceeds through a radical intermediate.c) It can proceed through different intermediates depending on the reaction conditions.d) It does not involve any intermediates.

Answer 6

Answer: c) It can proceed through different intermediates depending on the reaction conditions.Explanation: The mechanism of electrophilic aromatic substitution can involve carbocation intermediates in some cases and radical intermediates in other cases

Question 7

28. Which of the following factors can influence the reactivity of aromatic compounds in electrophilic aromatic substitution?a) The nature of the electrophile.b) The presence of substituents on the aromatic ring.c) The reaction temperature.d) All of the above.

Answer 7

Answer: d) All of the above.Explanation: All these factors play a role in the reactivity of aromatic compounds in electrophilic aromatic substitution:Electrophile: Stronger electrophiles are more reactive.Substituents: Activating groups increase reactivity

Question 8

29. Which of the following is NOT a characteristic of a good leaving group in a reaction?a) It should be a weak base.b) It should be able to stabilize a negative charge.c) It should be a good nucleophile.d) It should be a good electrophile.

Answer 8

Answer: c) It should be a good nucleophile.Explanation: A good leaving group is generally a weak base and a poor nucleophile. This allows it to depart readily fromthe molecule

Question 9

30. Which of the following compounds is a good example of a directing group in electrophilic aromatic substitution?a) Nitro group (-NO2)b) Methoxy group (-OCH3)c) Methyl group (-CH3)d) All of the above

Answer 9

Answer: d) All of the above.Explanation: Directing groups influence the position at which the electrophile attacks the aromatic ring. Nitro groups are deactivating and meta-directing

Question 10

31. Which of the following statements is TRUE about the reactivity of aromatic amines in electrophilic aromatic substitution?a) They are more reactive than benzene.b) They are less reactive than benzene.c) They have the same reactivity as benzene.d) The reactivity depends on the specific reaction conditions.

Answer 10

Answer: a) They are more reactive than benzene.Explanation: Aromatic amines are more reactive than benzene in electrophilic aromatic substitution due to the electron-donating effect of the amino group. This makes the ring more electron-rich and more susceptible to attack by electrophiles.

Question 11

32. Which of the following statements is TRUE about the reactivity of aromatic halides in electrophilic aromatic substitution?a) They are more reactive than benzene.b) They are less reactive than benzene.c) They have the same reactivity as benzene.d) The reactivity depends on the specific reaction conditions.

Answer 11

Answer: b) They are less reactive than benzene.Explanation: Halogen atoms are weakly deactivating groups. They withdraw electron density from the aromatic ring

Question 12

33. What is the major product of the reaction of benzene with acetyl chloride in the presence of aluminum chloride?a) Tolueneb) Acetophenonec) Benzaldehyded) Benzoic acid

Answer 12

Answer: b) AcetophenoneExplanation: This reaction is a Friedel-Crafts acylation

Question 13

34. Which of the following statements is TRUE about the reactivity of aromatic compounds in nucleophilic aromatic substitution?a) They are generally more reactive than in electrophilic aromatic substitution.b) They are generally less reactive than in electrophilic aromatic substitution.c) They are equally reactive in both electrophilic and nucleophilic aromatic substitution.d) The reactivity depends on the specific reaction conditions.

Answer 13

Answer: b) They are generally less reactive than in electrophilic aromatic substitution.Explanation: Nucleophilic aromatic substitution is generally less common than electrophilic aromatic substitution. Aromatic rings are electron-rich and not particularly susceptible to nucleophilic attack. However

Question 14

35. Which of the following statements is TRUE about the mechanism of nucleophilic aromatic substitution?a) It always proceeds through an SN2 reaction.b) It always proceeds through an SN1 reaction.c) It can proceed through different mechanisms depending on the reaction conditions.d) It does not involve any intermediates.

Answer 14

Answer: c) It can proceed through different mechanisms depending on the reaction conditions.Explanation: Nucleophilic aromatic substitution can occur through various mechanisms

Question 15

1. Explain the concept of aromaticity and its importance in organic chemistry.

Answer 15

Explanation:Aromaticity refers to a specific type of bonding in cyclic molecules. Aromatic compounds fulfill the following criteria: Cyclic structure* Planar structure* Continuous ring of p orbitals* Follows Huckel’s rule (4n+2 π electrons

Question 16

2. Describe the mechanism of electrophilic aromatic substitution with specific examples.

Answer 16

• Explanation: Electrophilic aromatic substitution is a type of reaction where an electrophile replaces a hydrogen atom on an aromatic ring. It involves the following steps:* Formation of an electrophile* Attack of the electrophile on the aromatic ring* Rearrangement to form a carbocation intermediate* Loss of a proton to regenerate the aromatic system* Examples: Nitration

Question 17

3. Compare and contrast the reactivity of benzene and cyclohexane. Explain the difference in their reactions with bromine.

Answer 17

• Explanation: Benzene is an aromatic hydrocarbon while cyclohexane is an aliphatic hydrocarbon.This difference in structure leads to significant differences in reactivity:* Benzene: Due to its aromatic character

Question 18

4. Discuss the properties and uses of phenol.

Answer 18

• Properties:* Weakly acidic due to resonance stabilization of the phenoxide ion.* Forms hydrogen bonds

Question 19

5. Explain the concept of a diazonium salt and its importance in organic synthesis.

Answer 19

• Explanation: Diazonium salts are unstable intermediates derived from aromatic amines. They have the general formula [Ar-N≡N]+X-

Question 20

6. Describe the mechanism of the Friedel-Crafts alkylation reaction. How does it differ from Friedel-Crafts acylation?

Answer 20

• Mechanism: The reaction proceeds via an electrophilic attack of an alkyl carbocation on the aromatic ring.* Formation of the alkyl carbocation (by reaction of the alkyl halide with the Lewis acid catalyst).* Attack of the alkyl carbocation on the aromatic ring.* Loss of a proton to regenerate the aromatic system.* Differences:* Alkylation: Uses an alkyl halide as the electrophile

Question 21

7. Discuss the properties and uses of heterocyclic aromatic compounds.

Answer 21

• Properties:* Contain at least one heteroatom (N

Question 22

8. Explain the concept of resonance in aromatic compounds and how it contributes to their stability.

Answer 22

• Explanation: Resonance refers to the delocalization of electrons in a molecule through the participation of multiple contributing structures. In aromatic compounds

Question 23

9. What are some examples of industrial applications of aromatic hydrocarbons?

Answer 23

• Examples:* Benzene: Used in the production of plastics

Question 24

10. Discuss the environmental impact of aromatic hydrocarbons and their potential health effects.

Answer 24

• Environmental Impact:* Aromatic hydrocarbons are volatile and can evaporate into the air.* Some aromatic hydrocarbons are persistent in the environment and can bioaccumulate in living organisms.* They can contaminate water sources and soil

Question 25

11. Explain the mechanism of the Friedel-Crafts acylation reaction. How does it differ from Friedel-Crafts alkylation?

Answer 25

• Mechanism: The reaction proceeds through an electrophilic attack of an acylium ion on the aromatic ring.* Formation of the acylium ion (by reaction of the acyl chloride with the Lewis acid catalyst).* Attack of the acylium ion on the aromatic ring.* Loss of a proton to regenerate the aromatic system.* Differences:* Acylation: Uses an acyl chloride as the electrophile

Question 26

12. Compare and contrast the reactivity of benzene and toluene in electrophilic aromatic substitution. Explain the directing effects of the methyl group.

Answer 26

• Explanation:* Benzene: Relatively unreactive due to its aromatic character.* Toluene: More reactive than benzene due to the electron-donating effect of the methyl group.* Directing effects of methyl group: Methyl group is an activating group and an ortho/para director. It increases electron density at the ortho and para positions

Question 27

13. Discuss the synthesis of aromatic compounds using the following methods: (a) Wurtz-Fittig reaction

Answer 27

(b) Grignard reaction

Question 28

14. Explain the concept of ortho meta and para directing groups in electrophilic aromatic substitution.

Answer 28

• Explanation: Directing groups are substituents on an aromatic ring that influence the position at which an incoming electrophile will attack.* Ortho/Para directors: These groups donate electron density to the ring

Question 29

15. What are some of the challenges and limitations associated with the synthesis of aromatic compounds?

Answer 29

• Challenges and Limitations:* Reactivity: Aromatic compounds can be challenging to functionalize due to their relative stability. Electrophilic aromatic substitution often requires harsh conditions.* Regioselectivity: Multiple sites on an aromatic ring can be susceptible to electrophilic attack