Amines: Class 12 Important Questions with Answers

Practice set: test yourself

Try every question before looking at the answers below. 64 or more out of 80 means you are ready for the board.

C. Very short answer (1 mark each)

1. IUPAC name of (CH₃)₂NC₂H₅.
2. Product of CH₃CN + LiAlH₄.
3. Name the reaction ArN₂Cl + CuCl/HCl.
4. Why is Fe/HCl preferred for reducing nitrobenzene?
5. Formula of sulphanilic acid.
6. Which is the strongest base: NH₃, CH₃NH₂, C₆H₅NH₂?
7. Product of aniline + (CH₃CO)₂O.
8. What is the smell of isocyanides?
9. Give the structure of p-aminoazobenzene.
10. Name a test for 1° aromatic amines.

D. Short answer I (2 marks each)

1. Write the Gabriel synthesis of ethanamine.
2. Write the Hoffmann reaction of acetamide.
3. Why is aniline less basic than ethylamine?
4. How will you distinguish ethylamine and diethylamine?
5. Arrange in increasing pKb: (CH₃)₂NH, CH₃NH₂, NH₃, C₆H₅NH₂.
6. Why does aniline give m-nitroaniline on direct nitration?
7. Convert benzene to aniline.
8. Write the coupling of benzenediazonium chloride with aniline.

Rough work

E. Short answer II (3 marks each)

1. Explain the Hinsberg test with equations.
2. Explain why the basicity order of ethylamines in water differs from that in the gas phase.
3. Write three reactions of benzenediazonium chloride where N₂ is replaced.
4. How is p-bromoaniline prepared from aniline? Why not directly?
5. Write A, B, C: CH₃CH₂Br → KCN → A → LiAlH₄ → B → HNO₂ → C.
6. Give three methods for preparing primary amines.

F. Long answer (5 marks each)

1. (a) A (C₇H₇NO) gives B by Hoffmann degradation; B with NaNO₂/HCl at 273 K gives C, which with phenol gives an orange dye D. Identify A–D. (b) Write all the reactions. (c) How will you get benzonitrile from C?
2. (a) Explain the basic character of amines with pKb values. (b) Why are aliphatic amines stronger bases than NH₃ and aromatic amines weaker? (c) Arrange: C₆H₅NH₂, p-CH₃C₆H₄NH₂, p-NO₂C₆H₄NH₂ by basicity.

G. HOTS (higher-order thinking)

1. Why are aliphatic diazonium salts unstable?
2. Why is sulphanilic acid a zwitter ion?
3. Why do 1° amines react with CHCl₃/KOH but 2° do not?
4. Why is benzylamine a stronger base than aniline?

20 MCQs

1. Strongest base in water
   (a) NH₃ (b) C₆H₅NH₂ (c) (CH₃)₂NH (d) (CH₃)₃N
2. Hoffmann degradation of propanamide
   (a) ethanamine (b) propanamine (c) butanamine (d) methanamine
3. Carbylamine test is for
   (a) 3° amines (b) amides (c) 2° amines (d) 1° amines
4. Hinsberg reagent
   (a) C₆H₅COCl (b) C₆H₅SO₂Cl (c) CHCl₃ (d) NaNO₂
5. Aniline + Br₂ water
   (a) p-bromoaniline (b) 2,4,6-tribromoaniline (c) o-bromoaniline (d) bromobenzene
6. Diazotisation temperature
   (a) 373 K (b) 453 K (c) 298 K (d) 273–278 K
7. ArN₂Cl + H₃PO₂
   (a) ArH (b) ArOH (c) ArCl (d) ArCN
8. Gas-phase basicity: highest
   (a) NH₃ (b) C₂H₅NH₂ (c) (C₂H₅)₃N (d) (C₂H₅)₂NH
9. Highest boiling isomer of C₃H₉N
   (a) (CH₃)₃N (b) all equal (c) CH₃NHC₂H₅ (d) CH₃CH₂CH₂NH₂
10. Gives alcohol with HNO₂
    (a) aniline (b) ethylamine (c) diethylamine (d) triethylamine
11. CH₃CN + LiAlH₄
    (a) CH₃NH₂ (b) CH₃CHO (c) CH₃CH₂NH₂ (d) CH₃CONH₂
12. Sandmeyer reagent for ArCl
    (a) CuCl/HCl (b) Cu + HCl (c) Cl₂ (d) HCl alone
13. Aniline + conc H₂SO₄, 453 K
    (a) anilinium sulphate only (b) sulphanilic acid (c) nitroaniline (d) benzene
14. Insoluble in alkali sulphonamide comes from
    (a) CH₃NH₂ (b) (CH₃)₃N (c) (CH₃)₂NH (d) NH₃
15. Weakest base
    (a) aniline (b) benzylamine (c) p-toluidine (d) p-nitroaniline
16. Coupling with phenol gives
    (a) p-hydroxyazobenzene (b) p-aminoazobenzene (c) phenol (d) benzene
17. Gabriel synthesis cannot give
    (a) aniline (b) ethanamine (c) propanamine (d) butanamine
18. Amine shape
    (a) planar (b) tetrahedral without lone pair (c) linear (d) pyramidal
19. Reduction of nitrobenzene (preferred)
    (a) Zn/NaOH (b) Fe/HCl (c) LiAlH₄ (d) NaBH₄
20. C₆H₅N₂⁺BF₄⁻ heated
    (a) C₆H₅Cl (b) C₆H₆ (c) C₆H₅F (d) C₆H₅OH

1 (c) · 2 (a) · 3 (d) · 4 (b) · 5 (b) · 6 (d) · 7 (a) · 8 (c) · 9 (d) · 10 (b) · 11 (c) · 12 (a) · 13 (b) · 14 (c) · 15 (d) · 16 (a) · 17 (a) · 18 (d) · 19 (b) · 20 (c)

Assertion–Reason (6)

(a) Both true, R explains A. (b) Both true, R does not explain A. (c) A true, R false. (d) A false, R true.

1. A: Aniline is a weaker base than methylamine. R: The lone pair of aniline is delocalised into the ring.
2. A: (CH₃)₃N is a weaker base in water than (CH₃)₂NH. R: Its ammonium ion is less solvated.
3. A: Aniline does not undergo Friedel–Crafts reaction. R: Aniline is an acid.
4. A: Ammonolysis gives a mixture of amines. R: The amine formed is also a nucleophile.
5. A: Tertiary amines do not react with Hinsberg's reagent. R: They have no H on N.
6. A: Benzenediazonium chloride is stable at room temperature for days. R: It is resonance stabilised.

Key: 1 (a) · 2 (a) · 3 (c) · 4 (a) · 5 (a) · 6 (d)

Answers to the practice set