61. Which of the following compounds is the least reactive towards nucleophilic addition reactions?
a) Formaldehyde
b) Acetaldehyde
c) Acetone
d) Benzaldehyde
Answer: d) Benzaldehyde
Explanation: Benzaldehyde is less reactive towards nucleophilic addition reactions due to the electron-withdrawing resonance effect of the benzene ring, which reduces the electrophilicity of the carbonyl carbon.
62. In the Hell-Volhard-Zelinsky reaction, which of the following reagents is used?
a) PCl₃ and Br₂
b) HCl and Br₂
c) HBr and Cl₂
d) NaOH and Cl₂
Answer: a) PCl₃ and Br₂
Explanation: In the Hell-Volhard-Zelinsky reaction, a carboxylic acid is halogenated at the alpha position using phosphorus trichloride (PCl₃) and bromine (Br₂).
63. Which of the following aldehydes will undergo oxidation most easily?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Propionaldehyde
Answer: a) Formaldehyde
Explanation: Formaldehyde is the simplest aldehyde and undergoes oxidation most easily to formic acid due to the absence of bulky groups around the carbonyl carbon.
64. Which of the following reactions is used to prepare ketones from acyl chlorides?
a) Friedel-Crafts acylation
b) Wolff-Kishner reduction
c) Clemmensen reduction
d) Wurtz reaction
Answer: a) Friedel-Crafts acylation
Explanation: In Friedel-Crafts acylation, an acyl chloride reacts with an aromatic compound in the presence of AlCl₃ to form a ketone.
65. Which of the following reactions can be used to synthesize acetaldehyde from ethyne?
a) Hydroboration-oxidation
b) Ozonolysis
c) Catalytic hydrogenation
d) Hydration in the presence of Hg²⁺
Answer: d) Hydration in the presence of Hg²⁺
Explanation: The hydration of ethyne (acetylene) in the presence of mercury(II) salts gives acetaldehyde through the formation of an enol, which tautomerizes to the aldehyde.
66. Which of the following will undergo decarboxylation most readily upon heating?
a) Benzoic acid
b) Oxalic acid
c) Malonic acid
d) Acetic acid
Answer: c) Malonic acid
Explanation: Malonic acid undergoes decarboxylation easily due to the presence of two carboxyl groups adjacent to each other, which facilitates the release of CO₂ upon heating.
67. In the reaction of an aldehyde with a cyanide ion, the intermediate product is:
a) Alcohol
b) Nitrile
c) Cyanohydrin
d) Acetal
Answer: c) Cyanohydrin
Explanation: The cyanide ion (CN⁻) adds to the carbonyl group of an aldehyde to form a cyanohydrin, which contains both a hydroxyl (-OH) group and a nitrile (-CN) group.
68. The Cannizzaro reaction involves:
a) Reduction of an aldehyde
b) Oxidation of an alcohol
c) Simultaneous oxidation and reduction of two molecules of an aldehyde
d) Oxidation of a ketone
Answer: c) Simultaneous oxidation and reduction of two molecules of an aldehyde
Explanation: The Cannizzaro reaction involves the disproportionation of two molecules of an aldehyde (without alpha-hydrogens), where one is oxidized to a carboxylic acid and the other is reduced to an alcohol.
69. Which of the following carboxylic acids undergoes Kolbe’s electrolysis?
a) Acetic acid
b) Benzoic acid
c) Formic acid
d) Oxalic acid
Answer: a) Acetic acid
Explanation: In Kolbe’s electrolysis, carboxylate anions, such as those from acetic acid, are electrolyzed to form alkanes. For acetic acid, this results in the formation of ethane.
70. The oxidation of acetaldehyde with potassium dichromate gives:
a) Ethanol
b) Acetone
c) Acetic acid
d) Formaldehyde
Answer: c) Acetic acid
Explanation: Potassium dichromate is a strong oxidizing agent, and it oxidizes acetaldehyde to acetic acid by converting the aldehyde group to a carboxyl group.
Leave a comment