NEET UG - Diazonium salts and their importance in synthetic organic chemistry Online Test (MCQ Quiz)

1. What is the general formula for a diazonium salt?

A) R-N=N-X B) R-N≡N⁺ X⁻ C) R-NH-NH₂⁺ X⁻ D) R-N₂-X

2. Diazotization is the process of converting primary aromatic amines into diazonium salts. What reagent is typically used for this reaction?

A) Sodium nitrite and hydrochloric acid B) Sodium nitrite and sulfuric acid C) Ammonia and sodium chloride D) Potassium permanganate and sulfuric acid

3. At what temperature range is the diazotization reaction usually carried out to ensure the stability of the diazonium salt?

A) 0-5 °C B) 20-25 °C C) 50-60 °C D) 80-100 °C

4. Which of the following is a characteristic property of aromatic diazonium salts?

A) They are highly stable at room temperature. B) They are generally soluble in organic solvents. C) They decompose rapidly at higher temperatures. D) They are colorless crystalline solids.

5. The Sandmeyer reaction is a crucial reaction involving diazonium salts. What is the typical outcome of the Sandmeyer reaction?

A) Replacement of the diazonium group with a hydroxyl group. B) Replacement of the diazonium group with a halogen or cyanide group. C) Coupling of the diazonium salt with a phenol. D) Reduction of the diazonium salt to a primary amine.

6. In the Sandmeyer reaction, which copper(I) salt is commonly used to introduce a chlorine atom onto the aromatic ring?

A) Copper(I) chloride (CuCl) B) Copper(I) bromide (CuBr) C) Copper(I) cyanide (CuCN) D) Copper(I) oxide (Cu₂O)

7. What is the Gattermann reaction, and how does it differ from the Sandmeyer reaction?

A) It uses copper powder instead of copper(I) salts and yields similar products. B) It uses metallic copper and yields different products. C) It is used for introducing nitro groups, unlike Sandmeyer. D) It is a coupling reaction, not a substitution.

8. When a diazonium salt reacts with water at higher temperatures, what is the major product formed?

A) Aniline B) Phenol C) Nitrobenzene D) Benzene

9. The reaction of a diazonium salt with hypophosphorous acid (H₃PO₂) is a method for:

A) Introducing a hydroxyl group. B) Introducing a halogen atom. C) Replacing the diazonium group with hydrogen. D) Forming an azo compound.

10. Which of the following is a characteristic reaction of diazonium salts that leads to the formation of azo compounds?

A) Sandmeyer reaction B) Gattermann reaction C) Azo coupling reaction D) Replacement by hydrogen

11. Azo coupling reactions typically occur between a diazonium salt and:

A) Another diazonium salt. B) A primary amine. C) A phenol or an aromatic amine. D) An alkyl halide.

12. The pH conditions for azo coupling are important. Coupling with phenols usually occurs under slightly alkaline conditions, while coupling with aromatic amines occurs under:

A) Strongly alkaline conditions. B) Neutral conditions. C) Slightly acidic conditions. D) Strongly acidic conditions.

13. What type of dye is formed as a result of azo coupling reactions?

A) Anthraquinone dyes B) Triphenylmethane dyes C) Azo dyes D) Indigo dyes

14. The presence of the -N=N- group in azo compounds is responsible for their characteristic:

A) Fluorescence B) Acidity C) Color D) Volatility

15. Which of the following compounds can be synthesized using diazonium salts as intermediates?

A) Alkanes B) Alkenes C) Aryl halides D) Esters

16. The Balz-Schiemann reaction is used to introduce which group onto an aromatic ring?

A) Chlorine B) Bromine C) Fluorine D) Iodine

17. In the Balz-Schiemann reaction, the diazonium salt is treated with:

A) Sodium fluoride B) Potassium fluoride C) Tetrafluoroborate anion (BF₄⁻) D) Hydrogen fluoride

18. The decomposition of diazonium salts is often accompanied by the evolution of:

A) Oxygen B) Nitrogen gas C) Carbon dioxide D) Hydrogen gas

19. Diazonium salts are important synthetic intermediates because they are versatile in undergoing:

A) Nucleophilic addition reactions. B) Electrophilic substitution reactions. C) Substitution reactions where the -N₂⁺ group acts as a good leaving group. D) Rearrangement reactions.

20. Which reaction allows for the conversion of an aniline derivative to a phenol derivative via a diazonium salt intermediate?

A) Sandmeyer reaction B) Hydrolysis of the diazonium salt C) Azo coupling D) Reduction

21. The synthesis of iodobenzene from aniline involves the formation of a diazonium salt followed by reaction with:

A) KI B) KBr C) KCl D) KF

22. Why are aliphatic diazonium salts less stable and generally not isolated?

A) They are highly aromatic. B) They readily lose nitrogen gas to form carbocations. C) They are ionic compounds. D) They are very soluble in water.

23. The diazonium group (-N₂⁺) is an excellent leaving group because it departs as:

A) A nitrogen molecule (N₂) B) A cyanide ion (CN⁻) C) A halogen molecule (X₂) D) A water molecule (H₂O)

24. Which of the following is NOT a typical synthetic application of diazonium salts?

A) Synthesis of azo dyes B) Synthesis of aryl halides C) Synthesis of aliphatic amines D) Synthesis of phenols

25. The introduction of a cyano group (-CN) onto an aromatic ring using a diazonium salt is achieved through which reaction?

A) Balz-Schiemann reaction B) Sandmeyer reaction with CuCN C) Gattermann reaction D) Hydrolysis

26. When benzene diazonium chloride is heated with copper powder and HCl, what is the product?

A) Phenol B) Chlorobenzene C) Benzene D) Aniline

27. Azo compounds are characterized by the presence of two aryl groups attached to the azo linkage (-N=N-). What is the typical synthesis route for these compounds?

A) Diazotization of two primary amines followed by coupling. B) Diazotization of one primary amine followed by azo coupling with an activated aromatic compound. C) Reaction of aniline with nitrogen gas. D) Oxidation of hydrazines.

28. The reaction of diazonium salts with SnCl₂/HCl leads to the formation of:

A) Aryl halides B) Phenols C) Hydrazines D) Azo compounds

29. Which of the following is a key reason for the importance of diazonium salts in synthetic organic chemistry?

A) Their ability to undergo addition reactions. B) Their role in forming carbon-carbon bonds. C) Their ability to act as electrophiles. D) Their ability to replace the -N₂⁺ group with a variety of functional groups.

30. If an aromatic amine is treated with NaNO₂ and H₂SO₄ at low temperature, and then the resulting diazonium salt is treated with H₂O/heat, what is the main product?

A) Aniline B) Phenol C) Nitrobenzene D) Benzene

31. The Schiemann reaction is a specific name for the Balz-Schiemann reaction when introducing:

A) Chlorine B) Bromine C) Fluorine D) Iodine

32. The synthesis of benzonitrile from aniline involves diazotization followed by reaction with:

A) CuCl B) CuBr C) CuCN D) KI

33. The diazonium group can be replaced by iodine using potassium iodide. This reaction is an example of:

A) Azo coupling B) Sandmeyer reaction C) Replacement by hydrogen D) Nucleophilic aromatic substitution

34. Which of the following is an example of an azo dye?

A) Methyl orange B) Phenolphthalein C) Alizarin D) Malachite green

35. The stability of diazonium salts is influenced by the aromatic ring. Electron-donating groups on the ring generally make the diazonium salt:

A) Less stable. B) More stable. C) Unreactive. D) Insoluble.

36. What is the role of copper(I) salts in the Sandmeyer reaction?

A) To catalyze the decomposition of the diazonium salt. B) To act as a nucleophile. C) To activate the incoming nucleophile. D) To facilitate the substitution of the diazonium group.

37. The reaction of diazonium salts with sodium borohydride (NaBH₄) can lead to:

A) Formation of phenols B) Formation of azo compounds C) Reduction to the parent hydrocarbon D) Halogenation

38. In the context of diazonium salts, 'diazotization' refers to:

A) The coupling of two diazonium salts. B) The decomposition of a diazonium salt. C) The conversion of a primary amine into a diazonium salt. D) The replacement of the diazonium group by hydrogen.

39. The synthesis of 4-bromophenol from 4-bromoaniline would involve diazotization followed by reaction with:

A) H₂O/heat B) CuBr C) KI D) H₃PO₂

40. A primary aromatic amine is converted to a diazonium salt using nitrous acid generated in situ. What is the active species of nitrous acid?

A) NO₂⁻ B) NO⁺ C) HNO₂ D) N₂O₃

41. Which of the following diazonium salt reactions is primarily used for the synthesis of biaryls?

A) Sandmeyer reaction B) Balz-Schiemann reaction C) Gomberg-Bachmann reaction D) Azo coupling

42. In the Gomberg-Bachmann reaction, a diazonium salt is reacted with another aromatic compound in the presence of:

A) Copper salts B) Strong acid C) Base D) A solvent like benzene or toluene

43. The replacement of the diazonium group by a hydroxyl group is often achieved by:

A) Heating the diazonium salt in aqueous acid. B) Reaction with sodium hydroxide. C) Reaction with water at room temperature. D) Reaction with dilute sulfuric acid.

44. Which of the following statements about diazonium salts is FALSE?

A) They are generally prepared at low temperatures. B) They are highly reactive intermediates. C) Aromatic diazonium salts are more stable than aliphatic ones. D) They readily undergo electrophilic substitution on the aromatic ring.

45. The reaction of benzene diazonium chloride with ethanol can lead to the formation of:

A) Phenol B) Benzene C) Ethyl phenyl ether D) Aniline

46. The Sandmeyer reaction is particularly useful for the synthesis of:

A) Alcohols B) Aldehydes C) Aryl halides and cyanides D) Esters

47. When benzene diazonium chloride is treated with potassium nitrite in the presence of copper, the product formed is:

A) Nitrobenzene B) Benzonitrile C) Chlorobenzene D) Phenol

48. The azo coupling reaction is an example of an electrophilic aromatic substitution where the diazonium ion acts as the:

A) Nucleophile B) Electrophile C) Leaving group D) Catalyst

49. Which of the following reactions involving diazonium salts is MOST suitable for preparing diarylamines?

A) Sandmeyer reaction B) Gomberg-Bachmann reaction C) Azo coupling D) Hydrolysis

Diazonium salts and their importance in synthetic organic chemistry - Online Test

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