41. Which of the following is the most basic compound?
a) Aniline
b) Ethylamine
c) Ammonia
d) Diphenylamine
Answer: b) Ethylamine
Explanation: Ethylamine (a primary aliphatic amine) is more basic than aromatic amines (like aniline or diphenylamine) because the electron-donating alkyl group increases the electron density on the nitrogen, making it more readily protonated.
42. Which of the following amines reacts with nitrous acid to form a stable diazonium salt?
a) Aniline
b) Benzylamine
c) Methylamine
d) Ethylamine
Answer: a) Aniline
Explanation: Aniline (an aromatic primary amine) reacts with nitrous acid to form a stable diazonium salt. Aliphatic amines like benzylamine and methylamine form unstable diazonium salts that decompose to alcohols.
43. Which of the following compounds will undergo the Hoffmann rearrangement?
a) Benzamide
b) Benzylamine
c) Benzene
d) Benzaldehyde
Answer: a) Benzamide
Explanation: The Hoffmann rearrangement (or Hoffmann bromamide reaction) involves the conversion of an amide (such as benzamide) to a primary amine with the loss of one carbon atom.
44. Which of the following is not a characteristic of nitro compounds?
a) They are generally explosive
b) They are basic
c) They are electron-withdrawing
d) They can undergo reduction to amines
Answer: b) They are basic
Explanation: Nitro compounds are not basic; in fact, they are typically acidic due to the electron-withdrawing nature of the nitro group (-NO₂).
45. What is the product when nitrobenzene is reduced with LiAlH₄?
a) Aniline
b) Phenol
c) Benzene
d) Nitroethane
Answer: a) Aniline
Explanation: Reduction of nitrobenzene with lithium aluminum hydride (LiAlH₄) results in the formation of aniline (C₆H₅NH₂) by reducing the nitro group (-NO₂) to an amino group (-NH₂).
46. Which of the following compounds will not undergo electrophilic substitution?
a) Nitrobenzene
b) Aniline
c) Toluene
d) Benzene
Answer: a) Nitrobenzene
Explanation: Nitrobenzene is deactivated toward electrophilic substitution due to the strong electron-withdrawing effect of the nitro group, making the ring less reactive compared to benzene, toluene, or aniline.
47. The major product when phenylhydroxylamine is reduced is:
a) Aniline
b) Hydrazobenzene
c) Nitrobenzene
d) Azobenzene
Answer: a) Aniline
Explanation: Phenylhydroxylamine (C₆H₅NHOH) is reduced to aniline (C₆H₅NH₂) through catalytic hydrogenation or by treatment with reducing agents.
48. The reaction of aniline with benzoyl chloride in the presence of a base gives:
a) Benzoic acid
b) Benzamide
c) N-Phenylbenzamide
d) Phenylhydrazine
Answer: c) N-Phenylbenzamide
Explanation: Aniline reacts with benzoyl chloride (C₆H₅COCl) in the presence of a base (Schotten-Baumann reaction) to form N-phenylbenzamide (C₆H₅NHCOC₆H₅) by acylation of the amino group.
49. The reaction of a primary amine with carbon disulfide (CS₂) followed by hydrolysis produces:
a) Thiourea
b) Isocyanide
c) Ammonia
d) Dithiocarbamic acid
Answer: d) Dithiocarbamic acid
Explanation: Primary amines react with carbon disulfide to form dithiocarbamates, which on hydrolysis yield dithiocarbamic acid (RNH-CS₂H). This reaction is utilized in the synthesis of organosulfur compounds.
50. In the Gabriel phthalimide synthesis, the phthalimide is treated with:
a) HCl
b) NaOH
c) NaOH and alkyl halide
d) Ammonium hydroxide
Answer: c) NaOH and alkyl halide
Explanation: In the Gabriel phthalimide synthesis, phthalimide is deprotonated by NaOH, forming a phthalimide anion, which then reacts with an alkyl halide (R-X) to form a primary amine after hydrolysis.
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