HSE Previous Questions on Amines
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A student was asked to convert nitrobenzene to benzene. Teacher suggested that he should first treat nitrobenzene with Sn and HCl and then proceed with the product obtained to get benzene. Write down the reaction involved in the above process.

NO₂

Sn+HCl

NH₂

N2+CI

NaNO2 & HCl 0-5°C

H3PO2 (aq)

What are the products obtained when aniline is treated with bromine water?

  • nitrobenzene
  • chlorobenzene
  • phenol
  • 2,4,6-Tribromoaniline (correct)

    • How will you convert nitrobenzene to aniline?

    NO 2 Sn+HCl or Fe+HCl NH₂

    Write down the isocyanide test for the primary amines.

    <p>Primary amines on heating with chloroform and alcoholic potassium hydroxide form foul smelling isocyanides or carbylamines. This reaction is known as the carbyl amine reaction or isocyanide test. Heat R-NH2 + CHCl3 + 3 КОН → R-NC + 3 KCl + 3 H2O</p> Signup and view all the answers

    Why did the student obtain only m-nitroaniline instead of p-nitroaniline when nitrating aniline in a strongly acidic medium?

    <p>In strongly acidic medium, aniline is protonated to form the anilinium ion which is meta directing. So a large amount of meta-nitroaniline is formed.</p> Signup and view all the answers

    Explain how the student should proceed to get p-nitroaniline from aniline.

    <p>For the preparation of p-nitroaniline, the –NH2 group is first deactivated by acetylation. The acetanilide thus formed is nitrated using nitrating mixture followed by hydrolysed. NH2 (CH3CO)2Q Pyridine NHCOCH3 HNO3, H2SO4, 288K NHCOCH3 NH2 OH or H NO2 p-Nitroacetanilide NO2 p-Nitroaniline</p> Signup and view all the answers

    How can you convert benzyl amine to benzoic acid?

    <p>Benzyl amine on diazotisation gives a 1º alcohol, benzyl alcohol. This on oxidation using acidified KMnO4, we get benzoic acid. CH2-NH2 NaNO2 &amp; HCl 0-5°C CH2-OH COOH KMnO4/ H+</p> Signup and view all the answers

    How can you convert benzoic acid to benzamide?

    <p>Benzoic acid on heating with ammonia we get benzamide which on treating with bromine and alkali to form benzoic acid. COOH NH3/Heat CONH2 NH2 Br2/KOH</p> Signup and view all the answers

    How is aniline converted to benzenediazonium chloride?

    <p>Aniline on treating with NaNO2 and HCl (or, with nitrous acid[HNO2]) we get benzene diazonium chloride. -NH2 NaNO2 &amp; HCI 0-5°C N2+CI</p> Signup and view all the answers

    How is chlorobenzene obtained from benzenediazonium chloride?

    <p>By treating benzenediazonium chloride with HCl in presence of cuprous chloride or Cu powder. (B)</p> Signup and view all the answers

    How is phenol obtained from benzenediazonium chloride?

    <p>By warming benzenediazonium chloride with water. (A)</p> Signup and view all the answers

    What is Hinsberg's reagent?

    <p>Benzenesulphonyl chloride (C6H5-SO2Cl)</p> Signup and view all the answers

    How will you distinguish primary, secondary and tertiary amines using Hinsberg's reagent?

    <p>Primary amines react with benzenesulphonyl chloride to form a precipitate of N-alkyl benzenesulphonamide, which is soluble in alkali. Secondary amines react with benzene sulphonyl chloride to give a precipitate of N,N-dialkylbenzene sulphonamide, which is insoluble in alkali. Tertiary amines do not react with benzenesulphonyl chloride</p> Signup and view all the answers

    Write the carbyl amine reaction.

    <p>R–NH2 + CHCl3 + 3 KOH → R–NC + 3 KCl + 3 H2O</p> Signup and view all the answers

    How will you convert aniline to phenol?

    <p>Treat aniline with sodium nitrite and hydrochloric acid at low temperature to form the diazonium chloride, then warm the diazonium chloride with water to get phenol.</p> Signup and view all the answers

    How can you convert an amide into an amine with one carbon atom less than that of the amide?

    <p>By Hoffmann bromamide degradation reaction [By treating with Br2 and ethanolic NaOH]</p> Signup and view all the answers

    How can you convert an amide into an amine containing the same number of carbon atoms as that in the amide?

    <p>By reduction using Lithium aluminium hydride (LiAlH4)</p> Signup and view all the answers

    Arrange the following compounds in the increasing order of their basic strength. NH3, C6H5NH2, CH3 - NH2, (CH3)2NH, (CH3)3N.

    <p>C6H5 NH2 &lt; NH3 &lt; (CH3)3N &lt; CH3 - NH2 &lt; (CH3)2NH (A)</p> Signup and view all the answers

    How will you convert aniline (C6H5 NH2) to chlorobenzene?

    <p>Refer the Answer of the Question number 5</p> Signup and view all the answers

    Arrange the following amines in increasing order of their basic strength. C6H5NH2, C2H5NH2, (C2H5)2NH, NH3.

    <p>C6H5NH2 &lt; NH3 &lt; C2H5 - NH2 &lt; (C2H5)2NH (D)</p> Signup and view all the answers

    Represent a reaction to explain the basic character of aniline.

    <p>C6H5NH2 + HCl → C6H5NH3+Cl-</p> Signup and view all the answers

    Name the reagents used in the Hoffmann bromamide reaction.

    <p>Bromine and ethanolic NaOH or KOH</p> Signup and view all the answers

    What is the significance of the Hoffmann bromamide reaction?

    <p>The reaction is used to prepare amine containing one carbon less than that present in the amide.</p> Signup and view all the answers

    Give one chemical test to distinguish between methyl amine and dimethyl amine. Write down the chemical reaction.

    <p>Carbyl amine reaction. Methyl amine gives this reaction, while dimethyl amine does not. Heat CH3-NH2 + CHCl3 + 3 КОН → CH3-NC + 3 KCl + 3 H2O</p> Signup and view all the answers

    Write a method of preparation of primary amines.

    <p>Hoffmann bromamide degradation reaction</p> Signup and view all the answers

    Describe a chemical reaction given only by primary amines.

    <p>Carbyl amine reaction or Isocyanide reaction</p> Signup and view all the answers

    What is diazotization?

    <p>Aniline on treating with NaNO2 and HCl (or, with nitrous acid[HNO2]) we get benzene diazonium chloride. This reaction is known as diazotisation</p> Signup and view all the answers

    Arrange the following amines in the increasing order of base strength. CH3 NH2, (CH3)2NH, (CH3)3N, C6H5NH2.

    <p>C6H5NH2 &lt; (CH3)3N &lt; CH3 - NH2 &lt; (CH3)2NH (D)</p> Signup and view all the answers

    Suggest the main product of the reaction: CH3NH2 + CHCl3 + alc. КОН

    <p>CH3-NC (Methyl isocyanide). The reaction is Carbyl amine reaction or Isocyanide reaction.</p> Signup and view all the answers

    Suggest the main product of the reaction: CH3CONH2 + Br2 + NaOH

    <p>CH3-NH2 (Methanamine). The reaction is Hoffmann bromamide degradation reaction.</p> Signup and view all the answers

    Write the IUPAC name of the following compound: H2N-(CH2)6-NH2

    <p>Hexane-1,6-diamine</p> Signup and view all the answers

    Which is a stronger base: CH3-NH2 or C6H5-NH2? Why?

    <p>CH3-NH2 due to the electron releasing inductive effect of CH3 group, it will readily accept H+ and hence it is more basic. (A)</p> Signup and view all the answers

    Arrange the following compounds in the increasing order of their basic strength: CH3-NH2, (CH3)2NH, NH3, C6H5-NH2

    <p>C6H5NH2 &lt; NH3 &lt; CH3 - NH2 &lt; (CH3)2NH (B)</p> Signup and view all the answers

    How will you carry out the Hoffmann bromamide reaction?

    <p>Amides on treating with Bromine and ethanolic solution of NaOH to give amines. R-CO-NH2 + Br2 + 4 NaOH → R-NH2 + Na2CO3 + 2 NaBr + 2 H2O</p> Signup and view all the answers

    How will you carry out the carbyl amine reaction?

    <p>Primary amines on heating with chloroform and alcoholic potassium hydroxide form foul smelling isocyanides or carbylamines. This reaction is known as the carbylamine reaction or isocyanide test. Heat R-NH2 + CHCl3 + 3 KOH → R-NC + 3 KCl + 3 H2O</p> Signup and view all the answers

    Represent the structure of secondary and tertiary amine

    <p>Secondary amine: R2NH Tertiary amine: R3N</p> Signup and view all the answers

    Why does aniline not undergo Friedel-Crafts reaction?

    <p>Since the catalyst, AlCl3, used in Friedel craft's reaction is a Lewis acid and Aniline is a Lewis base, they combine together to form salt. So the catalyst is not available for the reaction.</p> Signup and view all the answers

    Arrange the following compounds in the increasing order of their basic strength. NH3, C2H5NH2, C6H5NH2, (C2H5)2NH

    <p>C6H5NH2 &lt; NH3 &lt; C2H5 - NH2 &lt; (C2H5)2NH (A)</p> Signup and view all the answers

    Identify the products B and C write their formulae.

    <p>B is Aniline (C6H5-NH2) and B is 2,4,6 – Tribromoaniline</p> Signup and view all the answers

    The most basic compound among the following is: i) C2H5NH2 ii) C6H5NH2 iii) NH3 iv) (C2H5)2NH

    <p>(C2H5)2NH (A)</p> Signup and view all the answers

    Compound A is treated with Ethanolic NaCN to give the compound C2H5CN (B). Compound B on reduction gives compound C. Identify compounds A and C.

    <p>A is C2H5-Cl [Chloroethane] Or C2H5-Br[Bromoethane] and C is C2H5-CH2-NH2 [Propan-1-amine]</p> Signup and view all the answers

    Name the test used to identify primary amines using CHCl3 and ethanolic KOH.

    <p>Carbyl amine reaction or Isocyanide test</p> Signup and view all the answers

    How can it convert methyl iodide to ethanamine?

    <p>Methyl iodide + ethanolic KCN → Ethane nitrile OR, CH3-I + KCN(alc) → CH3-CN → CH3-CH2-NH2 H2/Ni → Ethanamine</p> Signup and view all the answers

    Gabriel synthesis is used for the preparation of which type of amines? Primary ii) Secondary iii) Tertiary iv) Quaternary

    <p>primary (B)</p> Signup and view all the answers

    Complete the following equations: (a) R-NH2 + CHCl3 + 3 KOH (b) NH2 Con: H2SO4 →?

    <p>(a) R-NC (Alkyl isocyanide or alkyl carbyl amine) (b) Anilinium hydrogen sulphate [which n heating gives sulphanilic acid] OR, NH3+HSO4</p> Signup and view all the answers

    The reaction in which an amide is converted into a primary amine by the action of Br2 and alcoholic NaOH is known as...

    <p>Hoffmann Bromamide degradation Reaction</p> Signup and view all the answers

    How is a primary amine distinguished from a secondary amine using a chemical test?

    <p>Carbyl amine test: Primary amines on heating with chloroform and alcoholic potassium hydroxide form foul smelling isocyanides or carbylamines. This reaction is known as carbylamines reaction or isocyanide test.</p> Signup and view all the answers

    Explain the reaction of primary, secondary and tertiary amines with Hinsberg's reagent.

    <p>Primary amines react with benzenesulphonyl chloride to form a precipitate of N-alkyl benzenesulphonamide, which is soluble in alkali. Secondary amines react with benzene sulphonyl chloride to give a precipitate of N,N-dialkylbenzene sulphonamide, which is insoluble in alkali. Tertiary amines do not react with benzenesulphonyl chloride</p> Signup and view all the answers

    Complete the following table:

    <p>SI. Reactant Reagent Product Name of reaction No. 1. CH3CH2NH2 CHCI3/KOH(aq) CH3-CH2-NC Carbylamine reaction 2. CH3CONH2 Br2/KOH CH3NH2 Hoffmann Bromamide degradation Reaction 3. C6H5-NH2 NaNO2+HCI/273K C6H5N2+CI Diazotisation</p> Signup and view all the answers

    Arrange the following amines in the increasing order of basic strength: CH3NH2, C6H5NH2, (CH3)3N, (CH3)2NH

    <p>C6H5NH2 &lt; (CH3)3N &lt; CH3 - NH2 &lt; (CH3)2NH (C)</p> Signup and view all the answers

    Benzene sulphonyl chloride and aqueous NaOH can be used to distinguish three classes of amines such as primary, secondary and tertiary. (i) Name the above test. (ii) How will you distinguish between methyl amine and dimethyl amine using this test?

    <p>(i) Hinsberg Test (ii) Methyl amine (which is a primary amine) react with benzenesulphonyl chloride to form a precipitate of N-methyl benzenesulphonamide, which is soluble in alkali. Dimethyl amine(which is a secondary amine) react with benzene sulphonyl chloride to give a precipitate of N,N-dimethylbenzene sulphonamide, which is insoluble in alkali.</p> Signup and view all the answers

    Which of the following amine cannot be prepared by Gabriel Phthalimide synthesis?

    <p>NH2 CH2-NH2 (A)</p> Signup and view all the answers

    Explain the method to distinguish primary, secondary and tertiary amines. Also write the chemical equations involved.

    <p>Refer the Answer of the Question number 24</p> Signup and view all the answers

    Identify A, B, C and D in the following reactions: (i) Br2 A NaOH NH2 (ii) CH3-CH2-NH2 + CHCl3 + 3KOH (iii) NH2 Bromine Water C (iv) N₂+ CF. D + KCl + N2 Heat

    <p>(i) A is C6H5-CO-NH2 (Benzamide) (ii) B is CH3-CH2-NC (Ethyl isocyanide) (iii) C is 2,4,6-Tribromoaniline (iv) D is Iodobenzene or C6H5-I</p> Signup and view all the answers

    A white precipitate is obtained when aniline reacts with bromine water at room temperature. The chemical name of the precipitate is...

    <p>2,4,6-Tribromoaniline</p> Signup and view all the answers

    Study Notes

    HSE Previous Questions and Answers (Amines)

    • Question 1 (March 2009): Convert nitrobenzene to benzene. The reaction involves treating nitrobenzene with Sn and HCl, followed by processing the resulting product. The reaction is detailed in the answer.

    • Question 2 (March 2010):

    • Part a: Aniline treated with bromine water forms 2,4,6-Tribromoaniline.

    • Part b: Nitrobenzene is converted to aniline using Sn and HCl, or Fe and HCl.

    • Part c: The isocyanide test (or carbyl amine reaction) for primary amines involves heating with chloroform and alcoholic potassium hydroxide. This forms foul-smelling isocyanides or carbylamines.

    • Question 3 (March 2011):

    • Part a: A student attempting to prepare p-nitroaniline by nitrating aniline with concentrated nitric and sulfuric acid, mistakenly gets m-nitroaniline due to the meta-directing nature of the anilinium ion formed in the strongly acidic reaction medium.

    • Part b: The correct method for preparing p-nitroaniline from aniline involves first deactivating the NH2 group by acetylation to form acetanilide. This is then nitrated using a nitrating mixture, followed by hydrolysis.

    • Question 4 (March 2011): Amines are a versatile functional group useful in the preparation of various organic compounds. Transformations are mentioned with steps involved

    • Question 5 (SAY 2011):

    • Part a: Aniline is converted to benzenediazonium chloride by treating with NaNO2 and HCl (or, with nitrous acid [HNO2]).

    • Part b:

    • Chlorobenzene is obtained by treating benzenediazonium chloride with HCl in the presence of cuprous chloride or copper powder.

    • Phenol forms from benzenediazonium chloride by heating with water.

    • Question 6 (March 2012):

    • Part i: Hinsberg's reagent is benzenesulfonyl chloride (C6H5SO2Cl).

    • Part ii: Primary amines react with the reagent, forming a precipitate of N-alkylbenzenesulfonamide that is soluble in alkali. Secondary amines give a precipitate that is insoluble in alkali, and tertiary amines do not react.

    • Question 7 (SAY 2012):

    • Part a (i): Carbyl amine reaction (or isocyanide reaction) involves reacting a primary amine with chloroform and alcoholic potassium hydroxide to produce foul-smelling isocyanides.

    • Part a (ii): Converting aniline to phenol is covered elsewhere in the notes.

    • Part b (i) and (ii): Methods for converting amides into amines with fewer or equal carbon atoms are explained elsewhere in the notes.

    • Question 8 (March 2013):

    • Part a: The increasing order of basic strength is C6H5NH2 < NH3 < CH3NH2 < (CH3)2NH < (CH3)3N.

    • Part b: The conversion process of aniline (C6H5NH2) to chlorobenzene is found elsewhere in the notes.

    • Question 9 (SAY 2013):

    • Part a: The increasing order of basic strength is C6H5NH2 < NH3 < C2H5NH2 < (C2H5)2NH

    • Part b, c, d, e: Further reactions involving amines are detailed elsewhere.

    • Question 10 (March 2014):

    • Part a: Hoffman bromamide degradation reaction is a method to prepare primary amines.

    • Part b: The carbyl amine reaction is a reaction unique to primary amines.

    • Part c: Diazotization is an organic reaction used to convert aniline to benzenediazonium chloride using NaNO2 and HCl (or, with nitrous acid[HNO2]) to form benzene diazonium chloride in the reaction.

    • (Questions 11-44) continued in subsequent notes...

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    Description

    This quiz covers previous questions and answers related to amines, focusing on reactions involving nitrobenzene, aniline, and their transformations. It also includes details about specific tests for amines and common mistakes in nitration reactions. Assess your knowledge of organic chemistry with these targeted questions!

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