Qualitative tests for amines MCQs With Answer

Qualitative tests for amines MCQs With Answer are essential revision tools for B.Pharm students preparing for analytical and pharmaceutical chemistry exams. This concise guide focuses on qualitative analysis of amines, covering key reactions like Hinsberg test, nitrous acid (diazotization), carbylamine test, and coupling reactions used to distinguish primary, secondary and tertiary, aromatic and aliphatic amines. Each MCQ targets mechanism, reagents, conditions and characteristic observations to deepen conceptual understanding and practical identification skills. The set emphasizes exam-style reasoning, reagent selection, expected products and interpretation of results. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which reagent is commonly used in the Hinsberg test for distinguishing primary, secondary and tertiary amines?

• Benzenesulfonyl chloride
• Sodium nitrite
• Chloroform
• Acetic anhydride

Correct Answer: Benzenesulfonyl chloride

Q2. In the Hinsberg test, a primary amine gives a product that is soluble in alkali due to which functional group formation?

• Sulfonamide salt
• Nitroso derivative
• Isocyanide
• Ammonium chloride

Correct Answer: Sulfonamide salt

Q3. Which test produces a foul-smelling isocyanide when a primary amine is present?

• Carbylamine test
• Hinsberg test
• Nitrous acid test
• Sandmeyer reaction

Correct Answer: Carbylamine test

Q4. Treatment of an aromatic primary amine with NaNO2 and HCl at 0–5°C yields which key intermediate?

• Aromatic diazonium salt
• Nitrosamine
• Isocyanide
• Sulfonamide

Correct Answer: Aromatic diazonium salt

Q5. Which observation indicates that an aliphatic primary amine has reacted with nitrous acid?

• Evolution of nitrogen gas and formation of alcohol
• Formation of stable diazonium salt
• Formation of yellow nitrosamine oil only
• No observable change

Correct Answer: Evolution of nitrogen gas and formation of alcohol

Q6. Secondary amines treated with nitrous acid typically yield which type of compound?

• N-nitrosamines
• Diazonium salts
• Isocyanides
• Sulfonamide salts

Correct Answer: N-nitrosamines

Q7. Which amine type does NOT react to give a diazonium salt with cold NaNO2/HCl?

• Secondary and tertiary amines
• Aromatic primary amines
• Aliphatic primary amines
• Primary aromatic amines

Correct Answer: Secondary and tertiary amines

Q8. In the Hinsberg test, what is the expected result for a secondary amine?

• Insoluble sulfonamide (does not dissolve in NaOH)
• Soluble sulfonamide salt
• Foul-smelling isocyanide
• No reaction at all

Correct Answer: Insoluble sulfonamide (does not dissolve in NaOH)

Q9. Which reagent combination generates nitrous acid in situ for amine testing?

• Sodium nitrite and hydrochloric acid
• Sodium nitrite and sodium hydroxide
• Benzenesulfonyl chloride and pyridine
• Chloroform and alcoholic KOH

Correct Answer: Sodium nitrite and hydrochloric acid

Q10. Which qualitative test can distinguish an amine from an amide by simple solubility in dilute acids?

• Dissolution in dilute hydrochloric acid forms ammonium salt (amines dissolve)
• Hinsberg test for sulfonamide formation
• Carbylamine test producing isocyanide
• Nitrous acid diazotization

Correct Answer: Dissolution in dilute hydrochloric acid forms ammonium salt (amines dissolve)

Q11. Which product is expected when an aromatic diazonium salt couples with β-naphthol?

• Colored azo dye
• Isocyanide compound
• Alkyl alcohol
• Sulfonamide salt

Correct Answer: Colored azo dye

Q12. A tertiary amine subjected to Hinsberg reagent typically gives which observation?

• No reaction; remains insoluble
• Soluble sulfonamide salt
• Formation of isocyanide with foul odor
• Evolution of nitrogen gas

Correct Answer: No reaction; remains insoluble

Q13. Which test is particularly useful to confirm the presence of primary aliphatic amines by formation of an oily nitrene derivative with strong odor?

• Carbylamine test
• Hinsberg test
• Nitrous acid test
• Sandmeyer reaction

Correct Answer: Carbylamine test

Q14. A primary aromatic amine gives a positive carbylamine test. What is the typical product responsible for the characteristic odor?

• Isocyanide
• Sulfonamide
• Nitrosamine
• Diazonium chloride

Correct Answer: Isocyanide

Q15. Which condition is critical for the formation of stable aromatic diazonium salts during diazotization?

• Low temperature (0–5°C)
• High temperature (>50°C)
• Strong basic medium
• Anhydrous conditions

Correct Answer: Low temperature (0–5°C)

Q16. Which reaction is commonly used to replace the diazonium group with a halogen (Cl or Br) in aromatic chemistry?

• Sandmeyer reaction
• Hinsberg test
• Carbylamine reaction
• Nitrosation

Correct Answer: Sandmeyer reaction

Q17. In qualitative analysis, which test distinguishes primary from secondary amines by formation of a soluble salt on alkaline hydrolysis?

• Hinsberg test
• Carbylamine test
• Nitrous acid test
• Sandmeyer reaction

Correct Answer: Hinsberg test

Q18. During diazotization, which gas is evolved when an aliphatic primary amine reacts with nitrous acid?

• Nitrogen (N2)
• Oxygen (O2)
• Chlorine (Cl2)
• Carbon dioxide (CO2)

Correct Answer: Nitrogen (N2)

Q19. When a secondary aromatic amine is treated with NaNO2/HCl, what kind of species is generally formed?

• N-nitroso compound
• Stable diazonium salt
• Isocyanide
• Sulfonamide salt

Correct Answer: N-nitroso compound

Q20. Which of the following tests can differentiate aniline (aromatic primary amine) from cyclohexylamine (aliphatic primary amine)?

• Nitrous acid test: aromatic gives diazonium, aliphatic gives N2 and alcohol
• Hinsberg test only
• Both give identical results in all tests
• Carbylamine test yields no distinction

Correct Answer: Nitrous acid test: aromatic gives diazonium, aliphatic gives N2 and alcohol

Q21. A compound gives a blue complex with Cu2+ in alkaline medium, indicating which functional group commonly found in pharmaceutical analysis?

• Presence of free amine that complexes with Cu2+
• Presence of sulfonamide only
• Presence of diazonium salt
• Presence of isocyanide

Correct Answer: Presence of free amine that complexes with Cu2+

Q22. Which reagent is used to acylate amines and can help differentiate primary and tertiary amines?

• Acetic anhydride
• Sodium nitrite
• Chloroform and KOH
• Benzenesulfonyl chloride

Correct Answer: Acetic anhydride

Q23. In an MCQ context, which observation confirms a positive Hinsberg test for a primary amine after adding NaOH?

• Solution becomes clear as sulfonamide salt dissolves
• Strong foul odor appears immediately
• No change and insoluble solid remains
• Evolution of N2 gas

Correct Answer: Solution becomes clear as sulfonamide salt dissolves

Q24. Which structural feature prevents tertiary amines from forming sulfonamides in the Hinsberg test?

• No N–H proton available for sulfonylation
• Too nucleophilic nitrogen
• Steric hindrance prevents all reactions with any reagent
• They are already salts

Correct Answer: No N–H proton available for sulfonylation

Q25. What is the primary observable used to indicate formation of an aromatic diazonium salt in qualitative testing?

• Formation of a stable salt that couples to give colored dyes
• Immediate foul-smelling gas
• Complete insolubility in acids
• Formation of isocyanide odor

Correct Answer: Formation of a stable salt that couples to give colored dyes

Q26. Which reagent pair is used in the carbylamine test?

• Chloroform and alcoholic KOH
• Sodium nitrite and HCl
• Benzenesulfonyl chloride and pyridine
• CuCl and HCl

Correct Answer: Chloroform and alcoholic KOH

Q27. On diazotization followed by azo coupling, what does a brightly colored product indicate in pharmaceutical qualitative tests?

• Presence of primary aromatic amine capable of diazonium formation
• Presence of tertiary amine only
• Absence of any amine functionality
• Presence of aliphatic primary amine only

Correct Answer: Presence of primary aromatic amine capable of diazonium formation

Q28. Which of the following is a limitation of the carbylamine test?

• Produces foul-smelling isocyanides and requires volatile reagents
• Does not differentiate primary and secondary amines
• Requires very high temperatures unsuitable for lab
• Gives false positives with alcohols

Correct Answer: Produces foul-smelling isocyanides and requires volatile reagents

Q29. A sample gives a yellow oily product on nitrous acid treatment without gas evolution. Which amine type is likely present?

• Secondary amine (formation of nitrosamine)
• Primary aromatic amine
• Primary aliphatic amine
• Tertiary amine

Correct Answer: Secondary amine (formation of nitrosamine)

Q30. Which test is useful to convert aniline into phenol as part of identification via diazonium chemistry?

• Diazotization followed by hydrolysis at warm temperature
• Carbylamine reaction
• Hinsberg test
• Direct bromination only

Correct Answer: Diazotization followed by hydrolysis at warm temperature

Q31. In practical lab testing, why is diazotization performed at 0–5°C?

• To stabilize the diazonium ion and prevent decomposition
• To speed up formation of isocyanides
• To promote nitrosamine formation
• To prevent formation of sulfonamides

Correct Answer: To stabilize the diazonium ion and prevent decomposition

Q32. Which of the following statements about nitrosation of secondary amines is correct?

• They form N-nitroso compounds which can be detected by characteristic color or TLC
• They produce stable diazonium salts similar to aromatic primary amines
• They give foul-smelling isocyanides
• They are completely inert to nitrous acid

Correct Answer: They form N-nitroso compounds which can be detected by characteristic color or TLC

Q33. Which qualitative test would you choose first to check whether an unknown compound contains a basic nitrogen (amine)?

• Test solubility in dilute HCl (forms ammonium salt)
• Hinsberg test
• Carbylamine test
• Diazotization

Correct Answer: Test solubility in dilute HCl (forms ammonium salt)

Q34. A substance fails to react with benzenesulfonyl chloride but dissolves in dilute HCl. Which functional group is most likely present?

• Tertiary amine
• Primary amine
• Secondary amine
• Amide

Correct Answer: Tertiary amine

Q35. Which product results from nitrosation of tertiary amines under common test conditions?

• Generally no stable nitroso product; little observable change
• Stable diazonium salt
• Isocyanide formation
• Sulfonamide salt

Correct Answer: Generally no stable nitroso product; little observable change

Q36. Which test is most appropriate to detect a primary aromatic amine in a pharmaceutical impurity screen?

• Diazotization followed by azo coupling to give colored products
• Hinsberg test only
• Carbylamine test only
• Oxidation with KMnO4

Correct Answer: Diazotization followed by azo coupling to give colored products

Q37. Which reagent is commonly used to form diazonium salts that will be used in Sandmeyer reactions?

• Sodium nitrite and hydrochloric acid
• Benzenesulfonyl chloride
• Chloroform and KOH
• Sodium hydroxide alone

Correct Answer: Sodium nitrite and hydrochloric acid

Q38. Why are diazonium salts of aromatic amines important in qualitative identification?

• They form colored azo compounds upon coupling, enabling visual identification
• They are volatile and can be distilled
• They form isocyanides that smell strongly
• They are insoluble and precipitate immediately

Correct Answer: They form colored azo compounds upon coupling, enabling visual identification

Q39. Which observation during Hinsberg test confirms a secondary amine?

• Formation of an insoluble sulfonamide that does not dissolve in NaOH
• Clear solution after adding NaOH
• Foul odor of isocyanide
• Evolution of nitrogen gas

Correct Answer: Formation of an insoluble sulfonamide that does not dissolve in NaOH

Q40. For a rapid screening MCQ question, which test is simplest to perform to show an amine is basic?

• Add dilute HCl; formation of cloudy to clear aqueous ammonium salt indicates basic amine
• Perform Hinsberg test immediately
• React with chloroform and KOH
• Perform azo coupling

Correct Answer: Add dilute HCl; formation of cloudy to clear aqueous ammonium salt indicates basic amine

Q41. Which test would you avoid if the lab policy forbids generation of foul odours and volatile toxic isocyanides?

• Carbylamine test
• Hinsberg test
• Nitrous acid diazotization
• Azo coupling test

Correct Answer: Carbylamine test

Q42. How does a tertiary amine behave when treated with dilute HCl in qualitative testing?

• Forms a soluble ammonium salt
• Forms an insoluble sulfonamide
• Produces nitrogen gas
• Forms isocyanide

Correct Answer: Forms a soluble ammonium salt

Q43. In distinguishing benzylamine (primary aliphatic) from aniline (primary aromatic), which observation with NaNO2/HCl is diagnostic?

• Benzylamine evolves N2 and gives alcohol; aniline forms diazonium salt
• Both form stable diazonium salts
• Both produce isocyanides
• Neither reacts with NaNO2/HCl

Correct Answer: Benzylamine evolves N2 and gives alcohol; aniline forms diazonium salt

Q44. Which of the following is true about N-nitrosamines formed from secondary amines?

• They are often carcinogenic and require careful handling
• They are identical to diazonium salts
• They have characteristic isocyanide odour
• They readily form sulfonamide salts in NaOH

Correct Answer: They are often carcinogenic and require careful handling

Q45. During a qualitative test, an amine gives a colored precipitate upon coupling with β-naphthol at alkaline pH. What does this indicate?

• Presence of an aromatic diazonium ion from a primary aromatic amine
• Presence of a tertiary amine
• Presence of an aliphatic primary amine only
• Absence of any amine functionality

Correct Answer: Presence of an aromatic diazonium ion from a primary aromatic amine

Q46. Which reagent is used in the Hinsberg test to form a sulfonamide?

• Benzenesulfonyl chloride (Hinsberg reagent)
• Sodium nitrite
• Chloroform
• CuCl

Correct Answer: Benzenesulfonyl chloride (Hinsberg reagent)

Q47. For an unknown amine that gives no reaction with HCl, benzenesulfonyl chloride or NaNO2/HCl, which amine type is most likely?

• Weakly basic or sterically hindered tertiary amine
• Primary aromatic amine
• Primary aliphatic amine
• Secondary amine

Correct Answer: Weakly basic or sterically hindered tertiary amine

Q48. Why is temperature control important during qualitative diazotization of aromatic amines?

• Elevated temperatures decompose diazonium salts leading to loss of diagnostic products
• Higher temperatures favor isocyanide formation
• Cold temperatures prevent any reaction
• Temperature has no effect on diazotization

Correct Answer: Elevated temperatures decompose diazonium salts leading to loss of diagnostic products

Q49. Which safety consideration is most important when performing nitrosation tests on amines in a pharmaceutical lab?

• Avoid formation and exposure to N-nitrosamines due to toxicity and carcinogenicity
• Ensure formation of isocyanide smell is tolerated
• Use open flames to ensure reaction completion
• No special precautions are needed

Correct Answer: Avoid formation and exposure to N-nitrosamines due to toxicity and carcinogenicity

Q50. Which combined approach gives the most reliable qualitative identification of an unknown amine in B.Pharm practicals?

• Sequential testing: solubility in acid, Hinsberg test, nitrous acid test, carbylamine and coupling reactions
• Only Hinsberg test is sufficient
• Only carbylamine test is sufficient
• Only visual inspection of odor

Correct Answer: Sequential testing: solubility in acid, Hinsberg test, nitrous acid test, carbylamine and coupling reactions

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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