71. Which of the following reagents can convert a carboxylic acid into an ester?
a) HCl
b) NaOH
c) H₂SO₄
d) NaBH₄
Answer: c) H₂SO₄
Explanation: Sulfuric acid (H₂SO₄) acts as a catalyst in the esterification reaction, where a carboxylic acid reacts with an alcohol to form an ester and water.
72. Which of the following does not undergo an aldol condensation reaction?
a) Acetaldehyde
b) Benzaldehyde
c) Acetone
d) Propanal
Answer: b) Benzaldehyde
Explanation: Benzaldehyde does not undergo aldol condensation because it lacks alpha-hydrogens, which are required for the enolate formation step of the reaction.
73. Which of the following compounds reacts with a Grignard reagent to form a tertiary alcohol?
a) Formaldehyde
b) Acetone
c) Benzaldehyde
d) Acetaldehyde
Answer: b) Acetone
Explanation: Acetone reacts with a Grignard reagent to form a tertiary alcohol after hydrolysis.
74. The reaction of a carboxylic acid with ammonia forms:
a) Amine
b) Amide
c) Alcohol
d) Aldehyde
Answer: b) Amide
Explanation: The reaction of a carboxylic acid with ammonia (NH₃) results in the formation of an amide (RCONH₂) through a condensation reaction.
75. Which of the following reagents will oxidize a primary alcohol to an aldehyde but not to a carboxylic acid?
a) PCC (Pyridinium chlorochromate)
b) KMnO₄
c) K₂Cr₂O₇
d) Na₂Cr₂O₇
Answer: a) PCC (Pyridinium chlorochromate)
Explanation: PCC is a mild oxidizing agent that oxidizes primary alcohols to aldehydes without further oxidizing them to carboxylic acids.
76. Which of the following carboxylic acids has the highest acidity?
a) Acetic acid
b) Formic acid
c) Propanoic acid
d) Trifluoroacetic acid
Answer: d) Trifluoroacetic acid
Explanation: Trifluoroacetic acid is highly acidic due to the strong electron-withdrawing effect of the fluorine atoms, which stabilize the conjugate base (carboxylate anion).
77. Which of the following reagents will convert an aldehyde into a primary alcohol?
a) NaBH₄
b) H₂SO₄
c) KMnO₄
d) HNO₃
Answer: a) NaBH₄
Explanation: Sodium borohydride (NaBH₄) is a reducing agent that converts aldehydes into primary alcohols by reducing the carbonyl group.
78. Which of the following aldehydes does not undergo nucleophilic addition reactions?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Methanal
Answer: c) Benzaldehyde
Explanation: Benzaldehyde is less reactive towards nucleophilic addition due to the electron-withdrawing effect of the benzene ring, which stabilizes the carbonyl group.
79. Which of the following statements is correct about ketones?
a) Ketones can undergo oxidation to form primary alcohols
b) Ketones can be reduced to secondary alcohols
c) Ketones can be oxidized to carboxylic acids under mild conditions
d) Ketones undergo nucleophilic substitution reactions
Answer: b) Ketones can be reduced to secondary alcohols
Explanation: Ketones are reduced to secondary alcohols using reducing agents such as NaBH₄ or LiAlH₄.
80. Which of the following reactions is used to prepare benzaldehyde from benzyl chloride?
a) Oxidation with KMnO₄
b) Reduction with NaBH₄
c) Hydrolysis in the presence of dilute HCl
d) Hydrolysis in the presence of NaOH
Answer: d) Hydrolysis in the presence of NaOH
Explanation: Benzaldehyde can be prepared from benzyl chloride through basic hydrolysis, which removes the chlorine atom and forms the aldehyde group.
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