11. Which of the following reactions is used to prepare aniline from benzene?
a) Sandmeyer reaction
b) Gattermann reaction
c) Nitration followed by reduction
d) Friedel-Crafts alkylation
Answer: c) Nitration followed by reduction
Explanation: Aniline is prepared from benzene by first nitrating benzene to form nitrobenzene, followed by reduction of nitrobenzene to aniline using reducing agents like tin and hydrochloric acid.
12. In the reaction of aniline with acetic anhydride, the product formed is:
a) Acetanilide
b) Nitroaniline
c) Benzanilide
d) Aniline acetate
Answer: a) Acetanilide
Explanation: When aniline reacts with acetic anhydride (CH₃CO)₂O, it forms acetanilide (C₆H₅NHCOCH₃) via acetylation of the amino group. This reaction protects the amine group from further reactions.
13. What is the major product when nitrobenzene undergoes catalytic hydrogenation?
a) Aniline
b) Phenol
c) Benzylamine
d) Azobenzene
Answer: a) Aniline
Explanation: Catalytic hydrogenation of nitrobenzene (C₆H₅NO₂) with hydrogen (H₂) and a catalyst like palladium or platinum reduces the nitro group (-NO₂) to an amino group (-NH₂), forming aniline (C₆H₅NH₂).
14. Which of the following will not give a positive carbylamine test?
a) Aniline
b) Methylamine
c) Diethylamine
d) Ethylamine
Answer: c) Diethylamine
Explanation: The carbylamine test is used to detect primary amines. Only primary amines react with chloroform (CHCl₃) and alcoholic potassium hydroxide (KOH) to form isocyanides (foul-smelling compounds). Diethylamine (a secondary amine) will not give a positive result.
15. Reduction of nitrobenzene with zinc and ammonium chloride gives:
a) Aniline
b) Phenylhydroxylamine
c) Hydrazobenzene
d) Azobenzene
Answer: b) Phenylhydroxylamine
Explanation: Partial reduction of nitrobenzene with zinc dust and ammonium chloride (NH₄Cl) in neutral conditions yields phenylhydroxylamine (C₆H₅NHOH). Further reduction can produce aniline.
16. The reaction of methylamine with nitrous acid results in the formation of:
a) Methyl alcohol
b) Ethyl alcohol
c) Methanol
d) Nitromethane
Answer: a) Methyl alcohol
Explanation: When methylamine (CH₃NH₂) reacts with nitrous acid (HNO₂), it undergoes diazotization to form a diazonium salt, which then decomposes to form methyl alcohol (CH₃OH), nitrogen gas (N₂), and water.
17. Which of the following is a nucleophilic substitution reaction?
a) Conversion of aniline to diazonium salt
b) Conversion of nitrobenzene to aniline
c) Hoffmann bromamide reaction
d) Gabriel phthalimide reaction
Answer: d) Gabriel phthalimide reaction
Explanation: The Gabriel phthalimide reaction involves the nucleophilic substitution of a halide by the phthalimide anion to form a primary amine.
18. Which of the following reagents is used for the diazotization of aniline?
a) H₂SO₄
b) NaOH
c) HCl + NaNO₂
d) CH₃COOH
Answer: c) HCl + NaNO₂
Explanation: Diazotization of aniline is carried out by treating it with sodium nitrite (NaNO₂) and hydrochloric acid (HCl) at low temperatures (0-5°C). This forms the diazonium salt, which is used in various synthetic reactions.
19. When p-nitroaniline is treated with bromine water, the major product is:
a) Mono-bromoaniline
b) Di-bromoaniline
c) 2,4,6-Tribromoaniline
d) 3,5-Dibromo-4-nitroaniline
Answer: d) 3,5-Dibromo-4-nitroaniline
Explanation: In p-nitroaniline, the -NO₂ group is a strong electron-withdrawing group that deactivates the benzene ring toward electrophilic substitution, but the -NH₂ group directs bromine to the ortho and para positions relative to it. The product is 3,5-dibromo-4-nitroaniline.
20. Which of the following does not involve the formation of a diazonium salt?
a) Sandmeyer reaction
b) Gattermann reaction
c) Hoffmann bromamide reaction
d) Coupling reaction
Answer: c) Hoffmann bromamide reaction
Explanation: The Hoffmann bromamide reaction does not involve diazonium salts. It is used to convert amides into amines by using bromine and a strong base.
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