Chemistry Examplar Problems

I. Multiple Choice Questions (Type-I) 1. Which of the following is a 3° amine? (i) 1-methylcyclohexylamine (ii) Triethylamine (iii) tert-butylamine (iv) N-methylaniline 2. The correct IUPAC name for CH2==CHCH2 NHCH3 is (i) Allylmethylamine (ii) 2-amino-4-pentene (iii) 4-aminopent-1-ene (iv) N-methylprop-2-en-1-amine 3. Amongst the following, the strongest base in aqueous medium is ____________. (i) CH3NH2 (ii) NCCH2NH2 (iii) (CH3)2 NH (iv) C6H5NHCH3 4. Which of the following is the weakest Brönsted base? (i) (ii) (iii) (iv) CH3NH2 5. Benzylamine may be alkylated as shown in the following equation : CHCHNH + R—X ⎯⎯⎯⎯→ CHCHNHR 6522 652 Which of the following alkylhalides is best suited for this reaction through SN1 mechanism? (i) CH3Br (ii) C6H5Br (iii) C6H5CH2Br (iv) C2H5 Br 6. Which of the following reagents would not be a good choice for reducing an aryl nitro compound to an amine? (i) H2 (excess)/Pt (ii) LiAlH4 in ether (iii) Fe and HCl (iv) Sn and HCl 7. In order to prepare a 1° amine from an alkyl halide with simultaneous addition of one CH2 group in the carbon chain, the reagent used as source of nitrogen is ___________. (i) Sodium amide, NaNH2 (ii) Sodium azide, NaN3 (iii) Potassium cyanide, KCN N–K+ (iv) Potassium phthalimide, C6H4(CO)2 8. The source of nitrogen in Gabriel synthesis of amines is _____________. (i) Sodium azide, NaN3 (ii) Sodium nitrite, NaNO2 (iii) Potassium cyanide, KCN N–K+ (iv) Potassium phthalimide, C6H4(CO)2 9. Amongst the given set of reactants, the most appropriate for preparing 2° amine is _____. (i) 2° R—Br + NH3 (ii) 2° R—Br + NaCN followed by H2/Pt (iii) 1° R—NH2 + RCHO followed by H2/Pt (iv) 1° R—Br (2 mol) + potassium phthalimide followed by H3O+/heat 10. The best reagent for converting 2–phenylpropanamide into 2-phenylpropanamine is _____. (i) excess H2 (ii) Br2 in aqueous NaOH (iii) iodine in the presence of red phosphorus (iv) LiAlH4 in ether 11. The best reagent for converting, 2-phenylpropanamide into 1- phenylethanamine is ____. (i) excess H2/Pt (ii) NaOH/Br2 (iii) NaBH4/methanol (iv) LiAlH4/ether 12. Hoffmann Bromamide Degradation reaction is shown by __________. (i) ArNH2 (ii) ArCONH2 (iii) ArNO2 (iv) ArCH2NH2 13. The correct increasing order of basic strength for the following compounds is _________. (I) (II) (III) (i) II < III < I (ii) III < I < II (iii) III < II < I (iv) II < I < III 14. Methylamine reacts with HNO2 to form _________. (i) CH3—O—N==O (ii) CH3—O—CH3 (iii) CH3OH (iv) CH3CHO 15. The gas evolved when methylamine reacts with nitrous acid is __________. (i) NH3 (ii) N2 (iii) H2 (iv) C2H6 16. In the nitration of benzene using a mixture of conc. H2SO4 and conc. HNO3, the species which initiates the reaction is __________. (i) NO2 (ii) NO+ (iii) NO2+ (iv) NO2– 17. Reduction of aromatic nitro compounds using Fe and HCl gives __________. (i) aromatic oxime (ii) aromatic hydrocarbon (iii) aromatic primary amine (iv) aromatic amide 18. The most reactive amine towards dilute hydrochloric acid is ___________. (i) CH3—NH2 (ii) (iii) (iv) 19. Acid anhydrides on reaction with primary amines give ____________. (i) amide (ii) imide (iii) secondary amine (iv) imine + Cu/HCl ⎯⎯⎯⎯⎯→ 20. The reaction Ar Cl– ArCl + N + CuCl is named as _________. N2 2 (i) Sandmeyer reaction (ii) Gatterman reaction (iii) Claisen reaction (iv) Carbylamine reaction 21. Best method for preparing primary amines from alkyl halides without changing the number of carbon atoms in the chain is (i) Hoffmann Bromamide reaction (ii) Gabriel phthalimide synthesis (iii) Sandmeyer reaction (iv) Reaction with NH3 22. Which of the following compound will not undergo azo coupling reaction with benzene diazonium chloride. (i) Aniline (ii) Phenol (iii) Anisole (iv) Nitrobenzene 23. Which of the following compounds is the weakest Brönsted base? (i) (ii) (iii) (iv) 24. Among the following amines, the strongest Brönsted base is __________. (i) (ii) NH3 (iii) (iv) 25. The correct decreasing order of basic strength of the following species is _______. H2O, NH3, OH–, NH2– (i) NH– > OH– > NH > HO 2 3 2 (ii) OH – > NH2– > H2O > NH3 (iii) NH3 > H2O > NH2– > OH – (iv) H2O > NH3 > OH– > NH2– 26. Which of the following should be most volatile? (I) CHCHCHNH(II) (CH)N (III) (IV) CH3CH2CH3 3222 33 (i) II (ii) IV (iii) I (iv) III 27. Which of the following methods of preparation of amines will give same number of carbon atoms in the chain of amines as in the reactant? (i) Reaction of nitrite with LiAlH4. (ii) Reaction of amide with LiAlH4 followed by treatment with water. (iii) Heating alkylhalide with potassium salt of phthalimide followed by hydrolysis. (iv) Treatment of amide with bromine in aqueous solution of sodium hydroxide. II. Multiple Choice Questions (Type-II) Note : In the following questions two or more options may be correct. 28. Which of the following cannot be prepared by Sandmeyer’s reaction? (i) Chlorobenzene (ii) Bromobenzene (iii) Iodobenzene (iv) Fluorobenzene 29. Reduction of nitrobenzene by which of the following reagent gives aniline? (i) Sn/HCl (ii) Fe/HCl (iii) H2-Pd (iv) Sn/NH4OH 30. Which of the following species are involved in the carbylamine test? (i) R—NC (ii) CHCl3 (iii) COCl2 (iv) NaNO2 + HCl 31. The reagents that can be used to convert benzenediazonium chloride to benzene are __________. (i) SnCl2/HCl (ii) CH3CH2OH (iii) H3PO2 (iv) LiAlH4 32. The product of the following reaction is __________. (ii) (iii) (iv) 33. Arenium ion involved in the bromination of aniline is __________. (i) (ii) (iii) (iv) 34. Which of the following amines can be prepared by Gabriel synthesis. (i) Isobutyl amine (ii) 2-Phenylethylamine (iii) N-methylbenzylamine (iv) Aniline 35. Which of the following reactions are correct? 36. Under which of the following reaction conditions, aniline gives p-nitro derivative as the major product? (i) Acetyl chloride/pyridine followed by reaction with conc. H2SO4 + conc. HNO3. (ii) Acetic anyhdride/pyridine followed by conc. H2SO4 + conc. HNO3. (iii) Dil. HCl followed by reaction with conc. H2SO4 + conc. HNO3. (iv) Reaction with conc. HNO3 + conc.H2SO4. 37. Which of the following reactions belong to electrophilic aromatic substitution? (i) Bromination of acetanilide (ii) Coupling reaction of aryldiazonium salts (iii) Diazotisation of aniline (iv) Acylation of aniline III. Short Answer Type 38. What is the role of HNO3 in the nitrating mixture used for nitration of benzene? 39. Why is NH2 group of aniline acetylated before carrying out nitration? 40. What is the product when CHCHNH reacts with HNO? 41. What is the best reagent to convert nitrile to primary amine? 42. Give the structure of ‘A’ in the following reaction. 43. What is Hinsberg reagent? 44. Why is benzene diazonium chloride not stored and is used immediately after its preparation? 45. Why does acetylation of —NH2 group of aniline reduce its activating effect? 46. Explain why MeNH2 is stronger base than MeOH? 47. What is the role of pyridine in the acylation reaction of amines? 48. Under what reaction conditions (acidic/basic), the coupling reaction of aryldiazonium chloride with aniline is carried out? 49. Predict the product of reaction of aniline with bromine in non-polar solvent such as CS2. 50. Arrange the following compounds in increasing order of dipole moment. CHCHCH, CHCHNH, CHCHOH 51. What is the structure and IUPAC name of the compound, allyl amine? 52. Write down the IUPAC name of 53. A compound Z with molecular formula CHN reacts with CHSOCl to give a 6522 232332232 39 652 solid, insoluble in alkali. Identify Z. 54. A primary amine, RNH2 can be reacted with CH3—X to get secondary amine, R—NHCH3 but the only disadvantage is that 3° amine and quaternary ammonium salts are also obtained as side products. Can you suggest a method where RNH2 forms only 2° amine? 55. Complete the following reaction. 56. Why is aniline soluble in aqueous HCl? 57. Suggest a route by which the following conversion can be accomplished. 58. Identify A and B in the following reaction. 59. How will you carry out the following conversions? (i) toluene ⎯⎯⎯→ p-toluidine (ii) p-toluidine diazonium chloride ⎯⎯⎯→ p-toluic acid 60. Write following conversions: (i) nitrobenzene ⎯→ acetanilide (ii) acetanilide ⎯→ p-nitroaniline 61. A solution contains 1 g mol. each of p-toluene diazonium chloride and pnitrophenyl diazonium chloride. To this 1 g mol. of alkaline solution of phenol is added. Predict the major product. Explain your answer. 62. How will you bring out the following conversion? 63. How will you carry out the following conversion? NO2 ⎯⎯⎯→ NH2 64. How will you carry out the following conversion? NH2 NO2 ⎯⎯⎯→ Br 65. How will you carry out the following conversions? (i) (ii) IV. Matching Type Note : Match the items of Column I and Column II in the following questions. 66. Match the reactions given in Column I with the statements given in Column II. 67. Match the compounds given in Column I with the items given in Column II. Column I Column II (i) Ammonolysis (a) Amine with lesser number of carbon atoms (ii) Gabriel phthalimide synthesis (b) Detection test for primary amines. (iii) Hoffmann Bromamide reaction (c) Reaction of phthalimide with KOH and R—X (iv) Carbylamine reaction (d) Reaction of alkylhalides with NH3 Column I Column II (i) Benzene sulphonyl chloride (a) Zwitter ion (ii) Sulphanilic acid (b) Hinsberg reagent (iii) Alkyl diazonium salts (c) Dyes (iv) Aryl diazonium salts (d) Conversion to alcohols V. Assertion and Reason Type Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices. (i) Both assertion and reason are wrong. (ii) Both assertion and reason are correct statements but reason is not correct explanation of assertion. (iii) Assertion is correct statement but reason is wrong statement. (iv) Both assertion and reason are correct statements and reason is correct explanation of assertion. (v) Assertion is wrong statement but reason is correct statement. 68. Assertion : Acylation of amines gives a monosubstituted product whereas alkylation of amines gives polysubstituted product. Reason : Acyl group sterically hinders the approach of further acyl groups. 69. Assertion : Hoffmann’s bromamide reaction is given by primary amines. Reason : Primary amines are more basic than secondary amines. 70. Assertion : N-Ethylbenzene sulphonamide is soluble in alkali. Reason : Hydrogen attached to nitrogen in sulphonamide is strongly acidic. 71. Assertion : N, N-Diethylbenzene sulphonamide is insoluble in alkali. Reason : Sulphonyl group attached to nitrogen atom is strong electron withdrawing group. 72. Assertion : Only a small amount of HCl is required in the reduction of nitro compounds with iron scrap and HCl in the presence of steam. Reason : FeCl2 formed gets hydrolysed to release HCl during the reaction. 73. Assertion : Aromatic 1° amines can be prepared by Gabriel Phthalimide Synthesis. Reason : Aryl halides undergo nucleophilic substitution with anion formed by phthalimide. 74. Assertion : Acetanilide is less basic than aniline. Reason : Acetylation of aniline results in decrease of electron density on nitrogen. VI. Long Answer Type 75. A hydrocarbon ‘A’, (C4H8) on reaction with HCl gives a compound ‘B’, (C4H9Cl), which on reaction with 1 mol of NHgives compound ‘C’, (CHN). On reacting 3 411 with NaNO2 and HCl followed by treatment with water, compound ‘C’ yields an optically active alcohol, ‘D’. Ozonolysis of ‘A’ gives 2 mols of acetaldehyde. Identify compounds ‘A’ to ‘D’. Explain the reactions involved. 76. A colourless substance ‘A’ (C6H7N) is sparingly soluble in water and gives a water soluble compound ‘B’ on treating with mineral acid. On reacting with CHCl3 and alcoholic potash ‘A’ produces an obnoxious smell due to the formation of compound ‘C’. Reaction of ‘A’ with benzenesulphonyl chloride gives compound ‘D’ which is soluble in alkali. With NaNO2 and HCl, ‘A’ forms compound ‘E’ which reacts with phenol in alkaline medium to give an orange dye ‘F’. Identify compounds ‘A’ to ‘F’. 77. Predict the reagent or the product in the following reaction sequence. ANSWERS I. Multiple Choice Questions (Type-I) 1. (ii) 2. (iv) 3. (iii) 4. (i) 5. (iii) 6. (ii) 7. (iii) 8. (iv) 9. (iii) 10. (iv) 11. (ii) 12. (ii) 13. (iv) 14. (iii) 15. (ii) 16. (iii) 17. (iii) 18. (ii) 19. (i) 20. (ii) 21. (ii) 22. (iv) 23. (iii) 24. (iv) 25. (i) 26. (ii) 27. (iii) II. Multiple Choice Questions (Type-II) 28. (iii), (iv) 29. (i), (ii), (iii) 30. (i), (ii) 31. (ii), (iii) 32. (i), (ii) 33. (i), (ii), (iii) 34. (i), (ii) 35. (i), (iii) 36. (i), (ii) 37. (i), (ii) III. Short Answer Type 38. HNO3 acts as a base in the nitrating mixture and provides the electrophile, NO+ 2 . 39. See NCERT textbook for Class XII. 40. C6H5CH2OH 41. Reduction of nitriles with sodium/alcohol or LiAlH4 gives primary amine. 42. 43. Benzene sulphonylchloride. 44. Benzene diazonium chloride is very unstable. 45. See NCERT textbook for Class XII. 46. Nitrogen is less electronegative than oxygen therefore lone pair of electrons on nitrogen is readily available for donation. Hence, MeNH2 is more basic than MeOH. 47. Pyridine and other bases are used to remove the side product i.e. HCl from the reaction mixture. 48. Reaction is done in mild basic conditions. 49. A mixture of 2-bromoaniline and 4-bromoaniline is formed. (2-Bromoaniline) (4-Bromoaniline) 50. CHCHCH < CHCHNH < CHCHOH 51. CH2==CH—CH2—NH2, prop-2-en-1-amine 52. N, N-Dimethylbenzenamine 53. Z is an aliphatic amine which gives a solid insoluble in base. This implies that reaction with C6H5SO2Cl must give a product without any replaceable hydrogen attached to nitrogen. In other words, the amine must be a secondary amine. i.e. Z is ethylmethylamine. 32332232 Carbylamine reaction is shown by 1° amine only which results in the replacement of two hydrogen atoms attached to nitrogen atom of NH2 group by one carbon atom. On catalytic reduction the isocyanide will give a secondary amine with one methyl group. 55. The reaction exhibits azo-coupling of phenols. In mild alkaline conditions phenol moiety participates in the azo-coupling and para position of phenol is occupied. 56. Aniline forms the salt anilinium chloride which is water soluble. 57. 58. 59. 60. 61. This reaction is an example of electrophilic aromatic substitution. In alkaline medium, phenol generates phenoxide ion which is more electron rich than phenol and hence more reactive for electrophilic attack. The electrophile in this reaction is aryldiazonium cation. Stronger the electrophile faster is the reaction. p-Nitrophenyldiazonium cation is a stronger electrophile than p-toluene diazonium cation. Therefore, it couples preferentially with phenol. 62. 65. (i) (ii) Conversion (A) given below is same as in part (i) given above after that reaction (B) can be carried out. (A) (B) IV. Matching Type 66. (i) → (d) (ii) → (c) (iii) → (a) (iv) → (b) 67. (i) → (b) (ii) → (a) (iii) → (d) (iv) → (c) V. Assertion and Reason Type 68. (iii) 69. (iii) 70. (iv) 71. (ii) 72. (iv) 73. (i) 74. (iv) VI. Long Answer Type Addition of HCl has occurred on ‘A’. This implies ‘A’ is an alkene. Cl in compound ‘B’ is substituted by NH2 to give ‘C’. ‘C’ gives a diazonium salt with NaNO2/HCl that liberates N2 to give optically active alcohol. This means that ‘C’ is an aliphatic amine. Number of carbon atoms in amine is same as in compound ‘A’. Since products of ozonolysis of compound ‘A’ are CH3 — CH ==O and O ==CH—CH3. The compound ‘A’ is CH3—CH==CH—CH3 On the basis of structure of ‘A’ reactions can be explained as follows : (A) (B) (B) (C) (C) (D) 76. CH3 77. 1. Sn-HCl 2. 3. H2O/H+ NO2 NHCOCH3 5. H3PO2/H2O NO2 NCl 2

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