Distinction Tests — 1°, 2°, 3° amines
Nitrogen Compounds
8
JEE Qs
8%
Hard
60
min
Focus on the unique observable changes (gas evolution, precipitate formation, color changes, solubility, odor) for each amine type with specific reagents to quickly identify them in MCQs.
🧮 Key Formulas
✅ Key Points for JEE
- 1The Hinsberg test distinguishes 1°, 2°, and 3° amines based on the acidity of the sulfonamide product and its solubility in strong base (NaOH). 1° sulfonamides are acidic (due to H on N) and soluble, 2° sulfonamides are non-acidic and insoluble, and 3° amines do not react.
- 2The Nitrous Acid test (NaNO2/HCl at 0-5°C) provides varied observable results: 1° aliphatic amines liberate N2 gas; 1° aromatic amines form stable diazonium salts; 2° amines (aliphatic/aromatic) form yellow oily N-nitrosoamines; 3° aliphatic amines show complex decomposition without direct N2 evolution, while 3° aromatic amines undergo p-nitrosation.
- 3The Carbylamine (Isocyanide) test is specific to 1° amines (both aliphatic and aromatic), producing a characteristic foul-smelling isocyanide, while 2° and 3° amines do not react.
- 4The number of N-H hydrogens available for substitution or elimination dictates the reactivity patterns in most distinction tests (e.g., 1° has 2H, 2° has 1H, 3° has 0H).
- 5Temperature control (0-5°C) is critical for the nitrous acid test, especially for the stability of aromatic diazonium salts and preventing side reactions.
⚠️ Common Mistakes
- ✕Confusing the solubility of the N-alkylbenzenesulfonamide (from 1° amine) in alkali – it is soluble due to its acidic hydrogen.
- ✕Not remembering that primary aliphatic diazonium salts formed with HNO2 are highly unstable and immediately decompose to produce N2 gas, alcohols, and alkenes.
- ✕Incorrectly applying the Carbylamine test to secondary or tertiary amines, as it is only characteristic for primary amines.
- ✕Failing to differentiate the reaction products and observations for 3° aliphatic amines versus 3° aromatic amines with nitrous acid.
- ✕Ignoring the specific temperature requirement (0-5°C) for the nitrous acid test, which is crucial for distinguishing products and preventing decomposition.
📝 Practice Questions
See allQ56.Given below are two statements : Consider the following reaction (1) Both Statement I and Statement II are false (2) Statement I is true but Statement II is false (3) Statement I is false but Statement II is true (4) Both Statement I and Statement II are true
Q56.Identify correct statements : (A) Primary amines do not give diazonium salts when treated with NaNO2 in acidic condition. (B) Aliphatic and aromatic primary amines on heating with CHCl3 and ethanolic KOH form 2025 (28 Jan Shift 2) JEE Main Previous Year Paper carbylamines. (C) Secondary and tertiary amines also give carbylamine test. (D) Benzenesulfonyl chloride is known as Hinsberg's reagent. (E) Tertiary amines reacts with benzenesulfonyl chloride very easily. Choose the correct answer from the options given below : (1) (A) and (B) only (2) (D) and (E) only (3) (B) and (D) only (4) (B) and (C) only
Q68.Match the Compounds (List - I) with the appropriate Catalyst/Reagents (List - II) for their reduction into corresponding amines. Choose the correct answer from the options given below : (1) (A)-(II), (B)-(I), (C)-(III), (D)-(IV) (2) (A)-(III), (B)-(II), (C)-(IV), (D)-(I) (3) (A)-(II), (B)-(IV), (C)-(III), (D)-(I) (4) (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
Q58.The correct set of ions (aqueous solution) with same colour from the following is: 2025 (23 Jan Shift 1) JEE Main Previous Year Paper (1) Sc3+, Ti3+, Cr2+ (2) V2+, Cr3+, Mn3+ (3) Ti4+, V4+, Mn2+ (4) Zn2+, V3+, Fe3+
Q66. For reaction The correct order of set of reagents for the above conversion is : (1) Br2 ∣FeBr3, H2O(Δ), NaOH (2) H2SO4, Ac2O, Br2, H2O(Δ), NaOH (3) Ac2O, Br2, H2O(Δ), NaOH (4) Ac2O, H2SO4, Br2, NaOH
Q55.Total number of nucleophiles from the following is : ⊖ NH3, PhSH, (H3C)2 S, H2C = CH2, O H, H3O⊕, (CH3)2CO, ⇌NCH3 (1) 7 (2) 4 (3) 6 (4) 5
NCERT Chapters
- Class 12 Chemistry Ch 13: Amines