NEET Chemistry: Aldehydes and Ketones Practice Questions
10 free multiple-choice questions on Aldehydes and Ketones for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more Aldehydes and Ketones questions in the app →Q1. The reaction of an aldehyde with a Grignard reagent results in the formation of an alcohol. This reaction exemplifies which type of reaction at the carbonyl carbon?
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Correct answer: C — Nucleophilic addition
Grignard reagents act as nucleophiles, attacking the electrophilic carbon of the carbonyl group, which is characteristic of nucleophilic addition reactions.
Q2. Which of the following reactions is a key step in the synthesis of β-hydroxy carbonyl compounds from aldehydes?
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Correct answer: A — Aldol condensation
Aldol condensation is the reaction where an enolate attacks another carbonyl group, forming β-hydroxy carbonyl compounds, which is a primary reaction involving aldehydes and ketones.
Q3. Which of the following compounds undergoes nucleophilic addition reaction with Grignard reagents most readily?
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Correct answer: D — Formaldehyde
Ketones (like acetone) and aldehydes possess a polarized carbonyl group (C=O) with π-bond character, making the carbon atom electrophilic and susceptible to nucleophilic attack by Grignard reagents. Aldehydes are also highly reactive in this regard.
Q4. Which reagent is commonly used to distinguish between an aldehyde and a ketone based on their reactivity with haloform reagents?
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Correct answer: C — NaHSO₃
Sodium hypothiocyanate (NaHSO₃) test (or haloform test derivatives) is often used in introductory organic chemistry to probe the difference in oxidation states and reactivity between aldehydes and ketones, although specific differentiation tests are more common.
Q5. In the Aldol condensation reaction, the reaction is usually base-catalyzed. What is the primary role of the base in this reaction?
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Correct answer: A — To facilitate enolization and subsequent nucleophilic attack
The base removes an α-hydrogen from the carbonyl compound to form an enolate ion, which then acts as a nucleophile to attack another carbonyl group.
Q6. Which chemical test is commonly used to distinguish between an aldehyde and a ketone based on their reaction with Fehling's solution?
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Correct answer: A — Fehling's test
Fehling's test is a qualitative test used to distinguish between aldehydes (which reduce Fehling's solution) and ketones (which do not reduce it).
Q7. The reaction of a ketone with an excess Grignard reagent leads to the formation of a:
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Correct answer: B — Tertiary alcohol
Ketones react with Grignard reagents to form an intermediate alkoxide which yields a tertiary alcohol after protonation, assuming standard conditions where excess reagent is used.
Q8. Which one of the following reagents is generally used to convert an aldehyde into a carboxylic acid under basic conditions, leading to aldol condensation products?
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Correct answer: C — Sodium hydroxide (NaOH)
Sodium hydroxide (or an alcoholic solution of NaOH) is a strong base used to catalyze the aldol condensation reaction between aldehydes and ketones, often forming β-hydroxy carbonyl compounds.
Q9. The Cannizzaro reaction is a disproportionation reaction specific to which type of carbonyl compound?
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Correct answer: D — Aliphatic aldehydes
The Cannizzaro reaction occurs exclusively for aldehydes that do not have α-hydrogens (like Benzaldehyde) or for aldehydes lacking α-hydrogens (like Formaldehyde).
Q10. In the reaction of an aldehyde with a mild reducing agent like NaBH₄, what is the primary outcome?
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Correct answer: A — Formation of an alcohol
Mild reducing agents like NaBH₄ selectively reduce the carbonyl group of aldehydes and ketones to the corresponding secondary or primary alcohols, respectively.
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