Diazonium salts and their synthetic importance - Question Bank

1. The reaction of a diazonium salt with sodium nitrite in the presence of copper powder can introduce a nitro group into the aromatic ring. This is a variation of:
A) Gattermann reaction
B) Sandmeyer reaction
C) Schiemann reaction
D) Azo coupling
2. The Balz-Schiemann reaction is specifically used for the synthesis of:
A) Aryl fluorides
B) Aryl chlorides
C) Aryl bromides
D) Aryl iodides
3. Which of the following diazonium salt reactions results in the formation of nitrogen gas as a byproduct?
A) Sandmeyer reaction
B) Azo coupling
C) Diazotization
D) All of the above
4. The synthesis of substituted benzoic acids from substituted anilines often involves diazotization followed by:
A) Reaction with CuCN/KCN and subsequent hydrolysis
B) Direct oxidation
C) Reduction
D) Halogenation
5. Which of the following is a characteristic property of diazonium salts that enables their use in coupling reactions?
A) Electrophilic nature of the diazonium ion
B) Nucleophilic nature of the diazonium ion
C) Strong oxidizing ability
D) Strong reducing ability
6. The reaction of benzenediazonium chloride with sodium borohydride (NaBH₄) can lead to:
A) Benzene
B) Aniline
C) Phenol
D) Chlorobenzene
7. What is the primary reason for the synthetic utility of diazonium salts?
A) The diazonium group can be easily replaced by a variety of nucleophiles
B) They are extremely stable compounds
C) They readily undergo electrophilic substitution
D) They are highly colored and used as indicators
8. The Sandmeyer reaction is a method for the replacement of the diazonium group by:
A) Halogens or cyano group
B) Hydrogen or hydroxyl group
C) Alkyl groups
D) Amino group
9. Which reaction is most suitable for synthesizing fluorobenzene from aniline?
A) Balz-Schiemann reaction
B) Sandmeyer reaction
C) Gattermann reaction
D) Azo coupling
10. The conversion of a diazonium salt to an aryl boronic acid can be achieved using:
A) Boric acid and a base
B) Copper(I) cyanide
C) Potassium iodide
D) Hypophosphorous acid
11. In the azo coupling reaction, the diazonium ion acts as an:
A) Electrophile
B) Nucleophile
C) Radical
D) Oxidizing agent
12. Which of the following diazonium salt reactions is used to introduce an iodine atom into an aromatic ring?
A) Reaction with KI
B) Sandmeyer reaction with CuCl
C) Schiemann reaction
D) Reduction with H₃PO₂
13. The coupling of a diazonium salt with a compound containing an active methylene group is possible under specific conditions. This is an example of:
A) Azo coupling
B) Sandmeyer reaction
C) Schiemann reaction
D) Nucleophilic addition
14. The reason for the instability of diazonium salts is:
A) The strong tendency of the N₂ molecule to leave as a stable gas
B) The presence of the highly reactive diazonium group
C) Their high solubility in water
D) Their susceptibility to oxidation
15. Which reagent is used to convert aniline to benzenediazonium chloride?
A) NaNO₂ + HCl (0-5 °C)
B) KMnO₄
C) CrO₃
D) H₂SO₄ + KNO₃
16. The synthesis of 4-bromobenzoic acid from 4-aminobenzoic acid involves:
A) Diazotization followed by Sandmeyer reaction
B) Direct bromination
C) Reduction of nitro group
D) Friedel-Crafts acylation
17. What is the oxidation state of nitrogen in the diazonium group (-N₂⁺)?
A) +1
B) -1
C) 0
D) +3
18. The decomposition of diazonium salts in solution is an example of:
A) Nucleophilic substitution
B) Electrophilic substitution
C) Free radical substitution
D) Addition reaction
19. Diazonium salts are important intermediates in the synthesis of:
A) A wide range of substituted aromatic compounds
B) Aliphatic compounds only
C) Inorganic compounds
D) Simple hydrocarbons
20. Which of the following is NOT a synthetic application of diazonium salts?
A) Preparation of alkenes
B) Preparation of halobenzenes
C) Preparation of phenols
D) Preparation of azo dyes
21. When benzenediazonium chloride is treated with ethanol, the major products are:
A) Benzene and nitrogen gas
B) Phenol and nitrogen gas
C) Aniline and nitrogen gas
D) Chlorobenzene and nitrogen gas
22. The reaction of diazonium salts with ethanol can lead to:
A) Aromatic hydrocarbons and nitrogen gas
B) Phenols
C) Azo compounds
D) Halobenzenes
23. The replacement of the diazonium group by a hydrogen atom can be achieved using:
A) Hypophosphorous acid (H₃PO₂)
B) Water
C) Potassium iodide
D) Copper(I) cyanide
24. The reaction of benzenediazonium chloride with H₃PO₂ yields:
A) Benzene
B) Aniline
C) Phenol
D) Chlorobenzene
25. The reduction of diazonium salts with hypophosphorous acid (H₃PO₂) leads to the formation of:
A) Aromatic hydrocarbons
B) Phenols
C) Anilines
D) Halobenzenes
26. When benzenediazonium chloride couples with aniline in a weakly acidic medium, the product formed is:
A) p-Aminoazobenzene
B) o-Aminoazobenzene
C) Benzene
D) Aniline
27. When benzenediazonium chloride couples with phenol in alkaline medium, the product formed is:
A) p-Hydroxyazobenzene
B) o-Hydroxyazobenzene
C) Benzene
D) Aniline
28. Azo compounds are known for their use as:
A) Dyes
B) Explosives
C) Solvents
D) Acids
29. The product of an azo coupling reaction contains the characteristic functional group:
A) -N=N-
B) -NH₂
C) -OH
D) -CN
30. Azo coupling reactions are usually carried out in a medium that is:
A) Weakly acidic or weakly alkaline
B) Strongly acidic
C) Strongly alkaline
D) Neutral
31. Azo coupling reactions typically occur between a diazonium salt and:
A) An activated aromatic compound (like phenol or aniline)
B) An alkyl halide
C) An alkane
D) A carboxylic acid
32. The azo coupling reaction is characteristic of:
A) Diazonium salts
B) Primary amines
C) Secondary amines
D) Alcohols
33. Which of the following is used in the Schiemann reaction to introduce fluorine into the aromatic ring?
A) HBF₄
B) HCl
C) HBr
D) KI
34. In the Schiemann reaction, the diazonium salt is first treated with HBF₄ to form a diazonium tetrafluoroborate salt, which is then heated. This leads to the formation of:
A) Aryl fluoride
B) Aryl chloride
C) Aryl bromide
D) Aryl iodide
35. The conversion of a diazonium salt to an aryl fluoride is known as the:
A) Schiemann reaction
B) Sandmeyer reaction
C) Gattermann reaction
D) Balz-Schiemann reaction
36. When benzenediazonium chloride reacts with CuCN/KCN, the product is:
A) Benzonitrile
B) Aniline
C) Benzene
D) Chlorobenzene
37. The replacement of the diazonium group by a cyano group (-CN) can be achieved using:
A) CuCN/KCN
B) CuCl/HCl
C) CuBr/HBr
D) KI
38. The reaction of benzenediazonium chloride with potassium iodide (KI) yields:
A) Iodobenzene
B) Benzene
C) Aniline
D) Phenol
39. When benzenediazonium chloride is heated with water, the primary product formed is:
A) Phenol
B) Aniline
C) Benzene
D) Chlorobenzene
40. The Gattermann reaction is similar to the Sandmeyer reaction but uses:
A) Copper powder and the corresponding acid (e.g., Cu/HCl)
B) Copper(I) cyanide
C) Water
D) Potassium iodide
41. Which product is formed when benzenediazonium chloride reacts with CuBr/HBr?
A) Bromobenzene
B) Chlorobenzene
C) Aniline
D) Benzene
42. Which product is formed when benzenediazonium chloride reacts with CuCl/HCl?
A) Chlorobenzene
B) Benzene
C) Aniline
D) Phenol
43. In the Sandmeyer reaction, what is the role of copper(I) halide (CuX)?
A) Catalyst for the replacement of the diazonium group by halide
B) Oxidizing agent
C) Reducing agent
D) Solvent
44. The Sandmeyer reaction involves the conversion of a diazonium salt to:
A) A halobenzene using CuX (X = Cl, Br)
B) A phenol using H₂O
C) A nitrobenzene using NaNO₂
D) An aniline using H₂
45. Which of the following is a characteristic property of diazonium salts in aqueous solution?
A) They are generally unstable and decompose readily
B) They are highly stable and can be stored for long periods
C) They are highly reactive and undergo nucleophilic substitution readily
D) They are insoluble in water
46. Why is the preparation of diazonium salts carried out at low temperatures (0-5 °C)?
A) To prevent decomposition of the diazonium salt
B) To increase the solubility of the amine
C) To facilitate the reaction with nitrous acid
D) To prevent the formation of azo compounds
47. The reaction of a primary aromatic amine with nitrous acid in the presence of a mineral acid at low temperature (0-5 °C) yields:
A) A diazonium salt
B) A nitro compound
C) An azo compound
D) A nitrile
48. Diazonium salts are typically prepared from primary aromatic amines by treatment with:
A) Dilute HCl and NaNO₂
B) Concentrated H₂SO₄ and KNO₃
C) Dilute HBr and NaNO₂
D) Concentrated HCl and KNO₃
49. Which of the following is the general formula for diazonium salts?
A) R-N≡N⁺ X⁻
B) R-NH₂⁺ X⁻
C) R-N=N-R
D) R-N₂-R