JEE Advanced (Single Correct Type): Aldehydes, Ketones & Carboxylic Acids | Chapter-wise Tests for JEE Main & Advanced PDF Download

Q.1. Which of the reactions below can result in ketones?
(a) Oxidation of primary alcohols
(b) Oxidation of secondary alcohols
(c) Dehydrogenation of tertiary alcohols
(d) Dehydrogenation of primary alcohols

Correct Answer is option (b)
Ketones are formed when secondary alcohols are oxidised and dehydrogenated. Aldehydes are produced by the same processes with primary alcohols.

Q.2. Reactions occur between aldehydes and ketones.
(a) nucleophilic addition
(b) electrophilic substitution
(c) electrophilic addition
(d) nucleophilic substitution

Correct Answer is option (a)
The polar CO group in aldehydes and ketones consists of double bond. The nucleophile attacks the sp² hybridised carbon, shattering the double bond and converting it to sp³, resulting in the formation of a tetrahedral alkoxide intermediate. This goes through another quick step to create an additional product.

Q.3. Acetone combines with ethylene glycol in dry HCl gas to generate _________
(a) hemiacetals
(b) cyclic ketals
(c) cyclic acetals
(d) acetals

Correct Answer is option (b)
Dihydric alcohols, such as ethylene glycol, react immediately with aldehydes and ketones to generate cyclic acetals and cyclic ketals, respectively. Ethylene glycol ketals are another name for cyclic ketals.

Q.4. Which of the following compounds is formed when benzyl alcohol is oxidised with KMnO₄?
(a) CO₂ and H₂O
(b) Benzoic acid
(c) Benzaldehyde
(d) Benzophenone

Correct Answer is option (b)
When benzyl alcohol is oxidised with KMnO₄, benzoic acid is the result.

Q.5. Which of the following substances is the least water-soluble?
(a) Methanal
(b) Pentanal
(c) Propanone
(d) Ethanal

Correct Answer is option (b)
As polar carbonyl group may establish hydrogen bonds with water molecules, the lower aldehydes and ketones are miscible in water in all quantities. However, as the length of the alkyl chain grows longer, the solubility drops dramatically. Aldehydes and ketones with more than four carbon atoms are nearly water- insoluble.

Q.6. The Rosenmund reaction can produce which of the following carbonyl compounds?
(a) Methanal
(b) Benzaldehyde
(c) Butanone
(d) Acetone

Correct Answer is option (b)
The Rosenmund reaction, which involves replacing chloride with hydrogen, is only utilised to make aldehydes. Methanal cannot be produced from this process because the acyl chloride that corresponds to it, formyl chloride, is unstable at ambient temperature. Benzoyl chloride produces benzaldehyde.

Q.7. Which of the following reactions to a nucleophilic assault is the least reactive?
(a) Acetaldehyde
(b) Di Tert-Butyl ketone
(c) Diisopropyl ketone
(d) Butanone

Correct Answer is option (b)
When comparing these substances, the steric effects are taken into account. The tert-butyl groups on either side of the carbonyl atom of the  ketone are highly bulky. This reduces reactivity by increasing the hindrance to the approaching nucleophile.

Q.8. Which of the following is not a formaldehyde application?
(a) Preservation of biological specimens
(b) Preparation of acetic acid
(c) Silvering of mirrors
(d) Manufacturing of bakelite

Correct Answer is option (b)
Because formaldehyde has only one carbon atom, it cannot be employed as a starting material for the production of acetic acid. It is, nevertheless, utilised to make bakelite, glues, and polymeric items. In the silvering of mirrors, it also works as a reducing agent.

Q.9. At 287K, which of the following is a gas?
(a) Propanal
(b) Acetaldehyde
(c) Formaldehyde
(d) Acetone

Correct Answer is option (c)
At room temperature, methane is a foul-smelling gas. Ethanal is a volatile liquid that boils at 294 degrees Fahrenheit. At room temperature, other aldehydes and ketones exist as liquids or solids.

Q.10. Which of these has the least unpleasant odour?
(a) Methanal
(b) Butanal
(c) Propanal
(d) Ethanal

Correct Answer is option (b)
The odour gets less strong and more fragrant as the size of the aldehyde molecule grows. Methanal has the strongest odour of all the aldehydes.