Q.Describe any one method for the identification of primary, secondary and tertiary amines. Write the chemical equations also for the reactions involved.

Showing the 12 most recent of 15 on this concept.

1. CBSE 2026Set DZ1 markMCQ
   Q.Which test is used to differentiate between primary, secondary and tertiary amines?

   (a) Brady test

   (b) Tollen's test

   (c) Hinsberg test

   (d) Lucas test

   ›Reveal solutionSolution

   The Hinsberg test (with benzenesulphonyl chloride, $C_6H_5SO_2Cl$) tells 1°, 2° and 3° amines apart, so option (c) is correct.

   In the Hinsberg test the amine is treated with benzenesulphonyl chloride ($C_6H_5SO_2Cl$, Hinsberg's reagent) in the presence of KOH:

   • Primary amine → gives an N-substituted sulphonamide that has an acidic N–H; it dissolves in KOH (soluble product).
   • Secondary amine → gives an N,N-disubstituted sulphonamide with no N–H; it is insoluble in KOH. …

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2. CBSE 2026Set ANNUAL1 markMCQ
   Q.Identify the Hinsberg reagent:

   (a) benzene ring - CONH2 (benzamide)

   (b) benzene ring - O - COCl (phenyl chloroformate)

   (c) benzene ring - SO2Cl (benzenesulfonyl chloride)

   (d) CH3 - benzene ring - COCl (4-methylbenzoyl chloride)

   ›Reveal solutionSolution

   Hinsberg's reagent is benzenesulfonyl chloride; its differing reaction behaviour with 1 degree, 2 degree, and 3 degree amines is the basis of the classic Hinsberg test.

   Benzenesulfonyl chloride, C6H5-SO2Cl, reacts differently depending on the class of amine:

   • Primary amines form an N-substituted sulfonamide that has an acidic N-H, which dissolves in excess alkali (KOH) - giving a clear solution.
   • Secondary amines form an N,N-disubstituted sulfonamide with no acidic N-H, which is insoluble in alkali - it stays as a precipitate. …

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3. CBSE 2026Set ANNUAL1 markMCQ
   Q.Hinsberg reagent is:

   (a) C6H5SO2Cl

   (b) C6H5N2Cl

   (c) C6H5NO

   (d) C6H5SO3H

   ›Reveal solutionSolution

   Hinsberg's reagent is benzenesulphonyl chloride, C₆H₅SO₂Cl, used to distinguish 1°, 2°, and 3° amines.

   Hinsberg's reagent is benzenesulphonyl chloride (C₆H₅SO₂Cl). In the Hinsberg test, it reacts with a primary amine to give an N-alkylbenzenesulphonamide that is soluble in alkali (the remaining N–H is acidic due to the electron-withdrawing SO₂ group); with a secondary amine it gives a sulphonamide that is insoluble in alkali (no acidic N–H le …

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4. CBSE 2025Set D1 markMCQ
   Q.Which of the following is Hinsberg reagent?

   (a) Benzene sulphonyl chloride

   (b) Benzene sulphonic acid

   (c) Ethyl oxalate

   (d) Acetyl chloride

   ›Reveal solutionSolution

   Hinsberg's reagent = benzenesulphonyl chloride, C6H5SO2Cl.

   Hinsberg's reagent is benzenesulphonyl chloride (C6H5SO2Cl). It is used to distinguish the three classes of amines:

   • Primary amines form a sulphonamide that is soluble in alkali (has an acidic N-H). …

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5. CBSE 2025Set A1 mark
   Q.Write True or False: Hinsberg's reagent reacts with primary and secondary amines to form sulphonamides.

   ›Reveal solutionSolution

   Hinsberg's test uses benzenesulphonyl chloride to distinguish primary, secondary, and tertiary amines by whether/how a sulphonamide forms.

   Hinsberg's reagent is benzenesulphonyl chloride (C6H5SO2Cl). When treated with:

   • A primary amine: it forms an N-alkylbenzenesulphonamide (C6H5SO2NHR), which has an acidic N–H (due to the electron-withdrawing SO2 group) and so dissolves in alkali (KOH) to give a clear solution.
   • A secondary amine: it forms an N,N-dialkylbenzenesulphonamide (C6H5SO2NR2), which has no acidic hydrogen and stays insoluble in alkali. …

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6. CBSE 2025Set ANNUAL1 markMCQ
   Q.Hinsberg's reagent is -

   (a) C6H5SO2Cl

   (b) C6H5SO2Cl2

   (c) C6H5SOCl2

   (d) C6H5SO3Cl

   ›Reveal solutionSolution

   Hinsberg's reagent is benzenesulfonyl chloride, C6H5SO2Cl.

   In Hinsberg's test, an amine is treated with benzenesulfonyl chloride (Hinsberg's reagent) in the presence of aqueous KOH:

   • A primary amine forms an N-alkylbenzenesulfonamide with an acidic N-H, which dissolves in excess KOH (forms a soluble salt).
   • A secondary amine forms an N,N-dialkylbenzenesulfonamide with no acidic N-H, which is insoluble in KOH. …

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7. CBSE 2024Set A11 markMCQ
   Q.The reagents used to separate the mixture of methylamine and dimethylamine are :

   (a) $\text{CHCl}_3$ and $\text{HCl}$

   (b) $\text{C}_6\text{H}_5\text{SO}_2\text{Cl}$ and $\text{KOH}$

   (c) $\text{C}_6\text{H}_5\text{SO}_2\text{Cl}$ and $\text{HCl}$

   (d) $\text{CHCl}_3$ and $\text{KOH}$

   ›Reveal solutionSolution

   Hinsberg's reagent ($\text{C}_6\text{H}_5\text{SO}_2\text{Cl}$) with $\text{KOH}$ separates a 1° from a 2° amine, so the answer is (b).

   Methylamine is a primary amine and dimethylamine is a secondary amine. Hinsberg's reagent (benzenesulphonyl chloride, $\text{C}_6\text{H}_5\text{SO}_2\text{Cl}$) distinguishes them:

   • With methylamine (1°):

     $\text{C}_6\text{H}_5\text{SO}_2\text{Cl} + \text{H}_2\text{NCH}_3 \rightarrow \text{C}_6\text{H}_5\text{SO}_2\text{NHCH}_3 + \text{HCl}$

     The product still has an N–H whose proton is acidic (activated by the $-\text{SO}_2-$ group), so it dissolves in $\text{KOH}$ to give a soluble salt.

   • With dimethylamine (2°):

     $\text{C}_6\text{H}_5\text{SO}_2\text{Cl} + \text{HN(CH}_3)_2 \rightarrow \text{C}_6\text{H}_5\text{SO}_2\text{N(CH}_3)_2 + \text{HCl}$ …

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8. CBSE 2024Set B1 mark
   Q.Match the pairs correctly. Column A item: "Hinsberg's reagent". Column B options:

   (a) C6H5SO2Cl

   (b) Keratin

   (c) C6H5NH2

   (d) Rickets

   (e) C6H5N2Cl

   (f) Cobalt. Which option from Column B matches "Hinsberg's reagent"?

   ›Reveal solutionSolution

   Hinsberg's reagent is benzenesulphonyl chloride (C6H5SO2Cl), used in Hinsberg's test to distinguish primary, secondary and tertiary amines.

   In the Hinsberg test, an amine is treated with benzenesulphonyl chloride (C6H5SO2Cl) in the presence of KOH:

   • 1 degree amines give a sulphonamide that dissolves in excess KOH (the N-H is acidic enough to be deprotonated). …

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9. CBSE 2024Set ANNUAL1 markMCQ
   Q.Hinsberg's reagent which is used to test amines is

   (a) Benzene sulphonamide

   (b) Benzene diazonium chloride

   (c) Benzene sulphonyl chloride

   (d) Acetanilide

   ›Reveal solutionSolution

   Hinsberg's reagent is benzenesulphonyl chloride; it reacts differently with 1-degree, 2-degree, and 3-degree amines, which is the basis of the Hinsberg test used to distinguish them.

   C6H5SO2Cl (benzenesulphonyl chloride) reacts with:

   • Primary amines -> forms an N-alkyl benzenesulphonamide that has an acidic N-H (soluble in alkali, since the sulphonyl group makes the remaining N-H acidic).
   • Secondary amines -> forms an N,N-dialkyl benzenesulphonamide with no N-H left (insoluble in alkali). …

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10. CBSE 2024Set ANNUAL1 mark
    Q.Name a test to distinguish between aniline and N-methylaniline.

    ›Reveal solutionSolution

    The carbylamine (isocyanide) test is specific to primary amines, so it cleanly distinguishes aniline (primary) from $N$-methylaniline (secondary).

    When a primary amine is warmed with chloroform and alcoholic potassium hydroxide, it is converted into an extremely foul-smelling alkyl/aryl isocyanide (carbylamine):

    $C_6H_5NH_2 + CHCl_3 + 3KOH \xrightarrow{\Delta} C_6H_5NC\,(\text{phenyl isocyanide, offensive odour}) + 3KCl + 3H_2O$

    This reaction requires an $-NH_2$ group with two replaceable hydrogens on nitrogen to form the isocyanide's $N \equiv C$ linkage — a mechanistic requirement that only primary amines satisfy.

    • Aniline ($C_6H_5NH_2$) is a primary amine $\Rightarrow$ gives a positive carbylamine test (pungent, unpleasant smell of phenyl isocyanide). …

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11. CBSE 2024Set ANNUAL1 markMCQ
    Q.The primary, secondary and tertiary amines can be distinguished by -

    (a) Fehling's test

    (b) Tollen's test

    (c) Libermann test

    (d) Hinsberg's test

    ›Reveal solutionSolution

    Hinsberg's reagent (benzenesulphonyl chloride) reacts differently with 1°, 2°, and 3° amines, giving products with distinct solubility behaviour — this difference is the basis of the test.

    Hinsberg's test: the amine is treated with benzenesulphonyl chloride (C$_6$H$_5$SO$_2$Cl) in the presence of KOH:

    • 1° amine: $RNH_2 + C_6H_5SO_2Cl \rightarrow C_6H_5SO_2NHR$ (N-alkylbenzenesulphonamide). This product still has an acidic N–H (due to the electron-withdrawing SO$_2$ group), so it dissolves in excess KOH to give a soluble salt; on acidification, the sulphonamide is regenerated as a precipitate.
    • 2° amine: $R_2NH + C_6H_5SO_2Cl \rightarrow C_6H_5SO_2NR_2$. No N–H remains, so this product is insoluble in KOH and separates out directly as an oily/solid precipitate. …

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12. CBSE 2023Set BZ1 markMCQ
    Q.Hinsberg reagent is:

    (a) Ethyl oxalate

    (b) Trimethyl amine

    (c) Benzene sulphonyl chloride

    (d) Benzyl chloride

    ›Reveal solutionSolution

    Hinsberg's reagent is benzenesulphonyl chloride, $C_6H_5SO_2Cl$, used to distinguish primary, secondary and tertiary amines.

    …

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