71. Which of the following is formed when aniline reacts with bromine water?
a) Mono-bromoaniline
b) Di-bromoaniline
c) 2,4,6-Tribromoaniline
d) 2,6-Dibromoaniline
Answer: c) 2,4,6-Tribromoaniline
Explanation: Aniline reacts with bromine water to form 2,4,6-tribromoaniline because the amino group (-NH₂) is strongly activating, directing bromine substitution to the ortho and para positions.
72. The reduction of nitrobenzene with Zn and NH₄Cl gives:
a) Azobenzene
b) Aniline
c) Hydrazobenzene
d) Phenylhydroxylamine
Answer: d) Phenylhydroxylamine
Explanation: Reduction of nitrobenzene using zinc and ammonium chloride (NH₄Cl) yields phenylhydroxylamine (C₆H₅NHOH) as the intermediate product.
73. Which of the following is used to detect primary amines?
a) Hinsberg’s reagent
b) Lucas reagent
c) Tollen’s reagent
d) Benedict’s reagent
Answer: a) Hinsberg’s reagent
Explanation: Hinsberg’s reagent (benzenesulfonyl chloride) is used to differentiate between primary, secondary, and tertiary amines. Primary amines form sulfonamides, which are soluble in alkali.
74. Which of the following compounds gives a foul smell of isocyanide when heated with chloroform and alcoholic KOH?
a) Ethylamine
b) Acetamide
c) Aniline
d) Benzylamine
Answer: c) Aniline
Explanation: Aniline (C₆H₅NH₂) reacts with chloroform and alcoholic KOH in the Carbylamine reaction to produce phenyl isocyanide (C₆H₅NC), which has a characteristic foul odor.
75. Which of the following reactions will produce a primary amine with one less carbon atom?
a) Sandmeyer reaction
b) Hoffmann bromamide reaction
c) Gabriel phthalimide synthesis
d) Acetylation of aniline
Answer: b) Hoffmann bromamide reaction
Explanation: The Hoffmann bromamide reaction converts an amide to a primary amine with one less carbon atom by using bromine (Br₂) and sodium hydroxide (NaOH).
76. Which of the following amines reacts with nitrous acid to form a yellow oily liquid?
a) Aniline
b) Methylamine
c) Diethylamine
d) Benzylamine
Answer: b) Methylamine
Explanation: Methylamine (a primary aliphatic amine) reacts with nitrous acid to form methyl diazonium salt, which decomposes to form nitrogen gas and a yellow oily liquid (methanol).
77. Which reagent is used to carry out the reduction of nitro compounds to amines?
a) Fe/HCl
b) NaOH
c) H₂O₂
d) KMnO₄
Answer: a) Fe/HCl
Explanation: Iron (Fe) and hydrochloric acid (HCl) are commonly used to reduce nitro compounds to amines, as in the reduction of nitrobenzene to aniline.
78. What is the major product when aniline reacts with acetic anhydride?
a) p-Nitroaniline
b) Acetanilide
c) Aniline hydrochloride
d) Benzanilide
Answer: b) Acetanilide
Explanation: When aniline reacts with acetic anhydride, it forms acetanilide as the product through acetylation of the amino group (-NH₂).
79. Which of the following is least reactive towards nucleophilic substitution?
a) Nitrobenzene
b) Benzyl chloride
c) 2,4-Dinitrochlorobenzene
d) Benzylamine
Answer: a) Nitrobenzene
Explanation: Nitrobenzene is least reactive towards nucleophilic substitution due to the strong electron-withdrawing effect of the nitro group (-NO₂), which deactivates the benzene ring for such reactions.
80. Which of the following reactions involves the formation of a diazonium salt?
a) Nitration of benzene
b) Acetylation of aniline
c) Diazotization of aniline
d) Bromination of aniline
Answer: c) Diazotization of aniline
Explanation: Diazotization of aniline involves the reaction of aniline with NaNO₂ and HCl at low temperatures (0-5°C) to form a diazonium salt (C₆H₅N₂⁺Cl⁻).
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