HSSLive XII Chemistry Amines Past Paper Questions & Answers PDF

Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Previous HSE questions and Answers from the chapter “ Amines” 1. A student was asked to convert nitrobenzene to benzene. Teacher suggested that he should first treat nitrobenzene with...

Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Previous HSE questions and Answers from the chapter “ Amines” 1. 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. (3) [March 2009] Ans: N2+Cl – NaNO2 & HCl H3PO2 (aq) 0 -50C 2. Aromatic amines are important synthetic intermediates. a) What are the products obtained when aniline is treated with bromine water? (1) 0- b) How will you convert nitrobenzene to aniline? (1) c) Write down the isocyanide test for the primary amines. (1) [March 2010] Ans: a) 2,4,6-Tribromoaniline b) c) Primary amines on heating with chloroform and alcoholic potassium hydroxide form foul smelling isocyanides or carbylamines. This reaction is known as carbyl amine reaction or isocyanide test. 𝐻𝑒𝑎𝑡 R-NH2 + CHCl3 + 3 KOH → R-NC + 3 KCl + 3 H2O 3. a) A student tried to prepare p-nitroaniline by nitrating Aniline with Conc. HNO3 – Conc. H2SO4 mixture. But he got only m-nitroaniline. Why? (1½) b) Explain how he should proceed to get p-nitroaniline from aniline. (1½) [March 2011] Ans: a) 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. b) 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. 4. Amines are versatile functional group useful in the preparation of many organic compounds. How can you convert? i) CH2-NH2 COOH (1) to Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 1  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® ii) COOH NH2 (2) [March 2011] to Ans: (i) Benzyl amine on diazotisation gives a 10 alcohol, benzyl alcohol. This on oxidation using acidified KMnO4 , we get benzoic acid. CH2-NH2 CH2-OH COOH NaNO2 & HCl KMnO4/ H+ 0 - 50C (ii) Benzoic acid on heating with ammonia we get benzamide which on treating with Bromine and alkali to form Benzoic acid. COOH CONH2 NH2 NH3 /Heat Br2 /KOH → → 5. Aniline is an aromatic primary amine. Starting with aniline a number of organic compounds can be prepared. a) How is aniline converted to benzenediazonium chloride? (1) b) How are the following obtained from benzenediazonium chloride? i) Chlorobenzene ii) Phenol (2) [SAY 2011] Ans: (a) Aniline on treating with NaNO2 and HCl (or, with nitrous acid[HNO2]) we get benzene diazonium chloride. (b) (i) By treating benzenediazonium chloride with HCl in presence of cuprous chloride or Cu powder. (ii) By warming benzenediazonium chloride with water. Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 2  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® 6. Primary, secondary and tertiary amines can be distinguished by using Hinsberg’s reagent. i) What is Hinsberg’s reagent? ii) How will you distinguish primary, secondary and tertiary amines using this reagent? (3) [March 2012] Ans: (i) Benzenesulphonyl chloride (C6H5-SO2Cl) (ii) 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 7. a) Carbyl amines have an offensive smell. i) Write the carbyl amine reaction. (1) ii) How will you convert aniline to phenol? (1) b) How will you convert an amide into following? i) An amine with one carbon atom less than that of the amide. (1) ii) An amine containing same number of carbon atom as that in the amide. (1) [SAY 2012] Ans: a) Refer the Answer of the Question number 2. b) (i) By Hoffmann bromamide degradation reaction [By treating with Br2 and ethanolic NaOH] (ii) By reduction using Lithium aluminium hydride (LiAlH4). 8. Amines are basic in nature. a) Arrange the following compounds in the increasing order of their basic strength. NH3, C6H5 NH2, CH3 - NH2, (CH3)2NH, (CH3)3N. (1) b) How will you convert aniline (C6H5NH2) to chlorobenzene? (2) [March 2013] Ans: (a) C6H5 NH2 < NH3 < (CH3)3N < CH3 - NH2 < (CH3)2NH (b) Refer the Answer of the Question number 5. 9. Amines can be considered as derivatives of ammonia. a) Arrange the following amines in increasing order of their basic strength. C6H5NH2, C2H5NH2, (C2H5)2NH, NH3. (1) b) Represent a reaction to explain the basic character of aniline. (1) c) Name the reagents used in the Hoffmann bromamide reaction. (½) d) What is the significance of the above reaction? (½) e) Give one chemical test to distinguish between methyl amine and dimethyl amine. Write down the chemical reaction. (1) [SAY 2013] Ans: a) C6H5 NH2 < NH3 < C2H5 - NH2 < (C2H5)2NH b) Aniline reacts with HCl to form Anilinium chloride. Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 3  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® c) Bromine and ethanolic NaOH or KOH. d) The reaction is used to prepare amine containing one carbon less than that present in the amide. e) Carbyl amine reaction. Methyl amine gives this reaction, while dimethyl amine does not. 𝐻𝑒𝑎𝑡 CH3-NH2 + CHCl3 + 3 KOH → CH3-NC + 3 KCl + 3 H2O 10. a) Write a method of preparation of primary amines. (1) b) Describe a chemical reaction given only by primary amines. (1) c) What is diazotization? (1) [March 2014] Ans: (a) Hoffmann bromamide degradation reaction. (b) Carbyl amine reaction or Isocyanide reaction. (c) Aniline on treating with NaNO2 and HCl (or, with nitrous acid[HNO2]) we get benzene diazonium chloride. This reaction is known as diazotisation. 11. a) Amines are basic. Arrange the following amines in the increasing order of base strength. CH3 NH2, (CH3)2NH, (CH3)3N, C6H5NH2. (1) b) Two well-known reactions are given below. Suggest the main product of each reaction. CHCl3 +alc. KOH i) CH3NH2 → Br2 +NaOH ii) CH3CONH2 → (1 X 2 = 2) [SAY 2014] Ans: a) C6H5 NH2 < (CH3)3N < CH3 - NH2 < (CH3)2NH b) (i) CH3-NC (Methyl isocyanide). The reaction is Carbyl amine reaction or Isocyanide reaction. (ii) CH3-NH2 (Methanamine). The reaction is Hoffmann bromamide degradation reaction. 12. Amines are classified as primary, secondary and tertiary. a) Write the IUPAC name of the following compound: H2N-(CH2)6-NH2 (1) b) Which is stronger base: CH3-NH2 or C6H5-NH2? Why? (2) [March 2015] Ans: a) Hexane-1,6-diamine b) CH3-NH2. Due to the electron releasing inductive effect of CH3 group, it will readily accept H+ and hence it is more basic. [Or, In C6H5-NH2, the lone pair of electrons is in conjugation with the benzene ring and it is less available for protonation. So it is less basic.] 13. a) Aromatic and aliphatic amines are basic in nature like ammonia. Arrange the following compounds in the increasing order of their basic strength: CH3-NH2, (CH3)2NH, NH3, C6H5-NH2 (1) b) How will you carry out the following reactions? i) Hoffmann bromamide reaction ii) Carbyl amine reaction (2) [SAY 2015] Ans: a) C6H5 NH2 < NH3 < CH3 - NH2 < (CH3)2NH b) i) Hoffmann Bromamide degradation Reaction: 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 ii) Carbyl amine Reaction: Primary amines on heating with chloroform and alcoholic potassium hydroxide form foul smelling isocyanides or carbylamines. This reaction is known as carbylamine reaction or isocyanide test. 𝐻𝑒𝑎𝑡 R-NH2 + CHCl3 + 3 KOH → R-NC + 3 KCl + 3 H2O 14. Amines are classified as primary, secondary and tertiary amine. a) Represent the structure of secondary and tertiary amine. (1) Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 4  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® b) How will you convert nitrobenzene to aniline? (1) c) Aniline does not undergo Friedel-Crafts reaction. Why? (1) [March 2016] Ans: (a) OR, (b) Refer the Answer of the Question number 2 (a) (c) 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. 15. Amines are basic in nature. a) Arrange the following compounds in the increasing order of their basic strength. NH3, C2H5NH2, C6H5NH2, (C2H5)2NH (1) b) How will you convert aniline to chlorobenzene? (2) [SAY 2016] Ans: a) Refer the Answer of the Question number 9 (a) b) Refer the Answer of the Question number 5 16. a) Classify the following amines as primary, secondary and tertiary: (1) b) Identify the products B and C write their formulae. (2) [March 2017] Ans: a) (C2H5)NH Primary amine Secondary amine Secondary amine Primary amine b) B is Aniline (C6H5-NH2) and B is 2,4,6 – Tribromoaniline 17. a) The most basic compound among the following is: i) C2H5NH2 ii) C6H5NH2 iii) NH3 iv) (C2H5)2NH (1) Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 5  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® b) 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. (2) [SAY 2017] Ans: a) (C2H5)2NH b) A is C2H5-Cl [Chloroethane] Or C2H5-Br[Bromoethane] and C is C2H5-CH2-NH2 [Propan-1-amine] 18. Name the test used to identify primary amines using CHCl3 and ethanolic KOH. (1) Ans: Carbyl amine reaction or Isocyanide test 19. How can it convert methyl iodide to ethanamine? (2) [March 2018] 𝑅𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛 Ans: Methyl iodide + ethanolic KCN → Ethane nitrile → Ethanamine H2 /Ni OR, CH3-I + KCN(alc) → CH3-CN → CH3-CH2-NH2 20. Gabriel synthesis is used for the preparation of which type of amines? i) Primary ii) Secondary iii) Tertiary iv) Quaternary (1) Ans: (i) Primary 21. Complete the following equations: (2) [SAY 2018] Ans: (a) R-NC (Alkyl isocyanide or alkyl carbyl amine) (b) Anilinium hydrogen sulphate [which n heating gives sulphanilic acid] OR, NH3+HSO4- 22. The reaction in which an amide is converted into a primary amine by the action of Br 2 and alcoholic NaOH is known as ……………. (1) Ans: Hoffmann Bromamide degradation Reaction 23. How is a primary amine distinguished from a secondary amine using a chemical test? (2) [March 2019] Ans: 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. 24. Explain the reaction of primary, secondary and tertiary amines with Hinsberg’s reagent. (3) [SAY 2019] Ans: 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. Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 6  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Tertiary amines do not react with benzenesulphonyl chloride 25. Complete the following table : (3x1=3) Sl. Reactant Reagent Product Name of reaction No. 1. CH3CH2NH2 CHCl3/KOH(aq) ……………………… Carbylamine reaction 2. CH3CONH2 Br2/KOH CH3NH2 ………………………….. 3. ……………… NaNO2+HCl/273K C6H5N2+Cl- Diazotisation [March 2020] Ans: Sl. Reactant Reagent Product Name of reaction No. 1. CH3CH2NH2 CHCl3/KOH(aq) CH3-CH2-NC Carbylamine reaction 2. CH3CONH2 Br2/KOH CH3NH2 Hoffmann Bromamide degradation Reaction 3. C6H5-NH2 NaNO2+HCl/273K C6H5N2+Cl- Diazotisation 26. (a) Amines are basic. Arrange the following amines in the increasing order of basic strength: CH3NH2, C6H5NH2, (CH3)3N, (CH3)2NH (1) (b) 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. (1) (ii) How will you distinguish between methyl amine and dimethyl amine using this test? (1) [SAY 2020] Ans: (a) Refer the Answer of the Question number 13 (a) (b)(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. 27. Which of the following amine cannot be prepared by Gabriel Phthalimide synthesis? CH2-NH2 (A) CH3-NH2 (B) (C) CH3-CH2-NH2 (D) (B) Ans: (B) Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 7  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® 28. Explain the method to distinguish primary, secondary and tertiary amines. Also write the chemical equations involved. [March 2021] Ans: Refer the Answer of the Question number 24 29. Identify A, B, C and D in the following reactions : [SAY 2021] Ans: (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 30. A white precipitate is obtained when aniline reacts with bromine water at room temperature. The chemical name of the precipitate is _____. (1) Ans: 2,4,6-Tribromoaniline 31. Explain carbylamine reaction with equation. (2) Refer the Answer of the Question number 2 (c) 32. CH3 – NH2 is more basic than NH3 while C6H5 – NH2 is less basic than NH3. Explain. (2) [March 2022] Ans: Due to the electron releasing inductive effect of CH3 group, it will readily accept H and hence it is + more basic. But in C6H5-NH2, the lone pair of electrons is in conjugation with the benzene ring and it is less available for protonation. So it is less basic.] 33. Major product of the following reaction is: (1) Ans: p-Nitroaniline and m-Nitroaniline 34. (i) What is the chemical name of Hinsberg Reagent? (1) (ii) Give the use of this reagent. (1) Ans: (i) Benzene sulphonyl chloride is called Hinsberg reagent. (ii) It is used to distinguish the 3 types of amines. 35. Arrange the following in the decreasing order of basic strength : C6H5NH2, C2H5NH2, (C2H5)2 NH, NH3. (2) [SAY 2022] Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 8  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® Ans: Refer the Answer of the Question number 9 (a). 36. Aniline does not undergo Friedel craft’s reaction. Why ? (2) Ans: Aniline (a Lewis base) forms salt with aluminium chloride (a Lewis acid), which is used as catalyst in Friedel Craft’s reaction. Due to this, nitrogen of aniline acquires positive charge and hence acts as a strong deactivating group for further reaction. So it does not undergo Friedel-Crafts reaction. 37. (i) What is Carbylamine reaction ? (1) (ii) Explain why aniline is less basic than ammonia. (2) [March 2023] Ans: (i) Refer the Answer of the Question number 2 (c) (ii) Aniline is less basic than ammonia due to the following reasons: (i) In aniline (C6H5-NH2), the lone pair of electrons is in conjugation with the benzene ring and hence it is less available for protonation. (ii) Aniline is resonance stabilized. While, the anilinium ion formed by the protonation of aniline is not resonance stabilized. So aniline does not easily add proton, or it is less basic. 38. Identify X and Y in the following equations : Ans: (i) Chlorobenzene (C6H5-Cl) (ii) Phenol (C6H5-OH) 39. (i) Aniline is less basic than ammonia. Why ? (2) (ii) Name two reagents used to convert Nitrobenzene to aniline. (1) [SAY 2023] Ans: (i) Refer the Answer of the Question number 37 (ii) (ii) (a) Tin (Sn) & HCl [Or, iron & HCl] and (b) H2 gas in presence of Ni catalyst. 40. Among CH3NH2 and C6H5NH2, which is more basic? Give reason. (2) Refer the Answer of the Question number 12 (b) 41. Describe Hinsberg test to distinguish primary, secondary and tertiary amines. (3) [March 2024] Refer the Answer of the Question number 24 42. Explain carbylamine reaction. (2) Refer the Answer of the Question number 2 (c). 43. Complete the following reaction : (1½) Ans: Chlorobenzene Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 9  Join Now: https://join.hsslive.in Downloaded from https://www.hsslive.in ® 44. Arrange the following ethyl amines in the increasing order of their basic character in aqueous medium: (a) (C2H5)2NH (b) C2H5–NH2 (c) (C2H5)3N (1½) [SAY 2024] Ans: C2H5–NH2 < (C2H5)3N < (C2H5)2NH ##################################################################################### Amines – Prepared by Anil Kumar K L, PHSS Vandiperiyar, Idukki Page 10