41. Which of the following is the main product when acetone undergoes aldol condensation?
a) Acetic acid
b) Acetaldehyde
c) Mesityl oxide
d) Benzaldehyde
Answer: c) Mesityl oxide
Explanation: When acetone undergoes aldol condensation, it first forms a β-hydroxy ketone, which upon dehydration gives mesityl oxide (CH₃COCH=CH₂COCH₃).
42. Which of the following will not give a positive Schiff’s test?
a) Acetaldehyde
b) Formaldehyde
c) Benzaldehyde
d) Acetone
Answer: d) Acetone
Explanation: Schiff’s test is used to detect aldehydes. Ketones, such as acetone, do not react positively with Schiff’s reagent.
43. Which of the following reactions produces a carboxylic acid from an alkene?
a) Ozonolysis followed by oxidation
b) Hydroboration-oxidation
c) Wurtz reaction
d) Friedel-Crafts alkylation
Answer: a) Ozonolysis followed by oxidation
Explanation: Ozonolysis of an alkene cleaves the double bond to form aldehydes, which can be further oxidized to carboxylic acids.
44. Which of the following compounds does not undergo oxidation with Tollen’s reagent?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Acetone
Answer: d) Acetone
Explanation: Tollen’s reagent is specific for aldehydes. Acetone, being a ketone, does not undergo oxidation with Tollen’s reagent.
45. Which of the following carboxylic acids is the least acidic?
a) Formic acid
b) Acetic acid
c) Benzoic acid
d) Phenylacetic acid
Answer: d) Phenylacetic acid
Explanation: Phenylacetic acid is less acidic than benzoic acid because the phenyl group in phenylacetic acid is separated from the carboxyl group by a methylene (-CH₂-) group, reducing the electron-withdrawing effect.
46. Which of the following compounds gives a yellow precipitate with iodine and NaOH (Iodoform test)?
a) Ethanol
b) Propanol
c) Methanol
d) Isopropanol
Answer: d) Isopropanol
Explanation: Isopropanol contains the CH₃CHOH– group, which gives a positive iodoform test, resulting in the formation of yellow iodoform (CHI₃).
47. Which of the following acids will undergo decarboxylation most readily?
a) Acetic acid
b) Malonic acid
c) Oxalic acid
d) Succinic acid
Answer: b) Malonic acid
Explanation: Malonic acid undergoes decarboxylation easily because the reaction results in the formation of a stable carboxylate ion, followed by protonation to give acetic acid.
48. Which of the following aldehydes will undergo the Cannizzaro reaction?
a) Formaldehyde
b) Acetaldehyde
c) Benzaldehyde
d) Propanal
Answer: c) Benzaldehyde
Explanation: The Cannizzaro reaction is undergone by aldehydes that do not have alpha-hydrogens. Benzaldehyde, lacking alpha-hydrogens, undergoes the Cannizzaro reaction.
49. The product obtained from the reaction of formaldehyde with Grignard reagent followed by hydrolysis is:
a) Primary alcohol
b) Secondary alcohol
c) Tertiary alcohol
d) Ketone
Answer: a) Primary alcohol
Explanation: Formaldehyde reacts with a Grignard reagent to give a primary alcohol after hydrolysis.
50. The product of oxidation of an aldehyde with Fehling’s solution is:
a) Alcohol
b) Ketone
c) Carboxylic acid
d) Ester
Answer: c) Carboxylic acid
Explanation: Fehling’s solution oxidizes aldehydes to carboxylic acids by converting the aldehyde group (-CHO) to a carboxyl group (-COOH).
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