Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Aldehydes, Ketones and Carboxylic Acids

Question:

Answer the questions on the basis of passage given below:

As aldehydes & ketones possess the carbonyl functional group, they show similar reactions. They exhibit nucleophilic addition reactions, reduction, oxidations, reactions due to ∝-Hydrogen atom, and many other reactions, like Cannizzaro reaction to electrophilic substitution reactions (in case of aromatic aldehydes & ketones). These reactions help in the preparation of a number of important compounds, like acetic acid, vinyl acetate, polymers and in perfume and dye industries. Nucleophilic addition reactions form cyanohydrins. acetals, alcohols and N-substituted derivatives like imine, oxime, semicarbazone, phenylhydrazone & Schiff's base. Reactions due to ∝-hydrogen atoms help in formation of aldols and a, B-unsaturated aldehydes & ketones.

4-Hydroxy-4-methylpentan-2-one and 4-methylpent-3-en-2-one are the products obtained from 'A' by aldol condensation. 'A' is:

Options:

\(CH_3COCH_3\)

\(CH_3CHO\)

\(CH_3CH_2CH_2CH_2CHO\)

\(CH_3CH_2CH_2CHO\)

Correct Answer:

\(CH_3COCH_3\)

Explanation:

The correct answer is option 1. \(CH_3COCH_3\).

Aldol condensation involves the reaction of two molecules containing carbonyl groups (aldehydes or ketones) in the presence of a base to form a β-hydroxy carbonyl compound (aldol product). This aldol product can further undergo dehydration to form an α,β-unsaturated carbonyl compound.

Structure of the Products

4-Hydroxy-4-methylpentan-2-one:

This compound has a hydroxy group \(-OH\) on the 4th carbon, a ketone group \(-CO-\) at the 2nd carbon, and a methyl group \(-CH_3\) attached to the 4th carbon.

4-Methylpent-3-en-2-one

This compound has a double bond between the 3rd and 4th carbon and a ketone group at the 2nd carbon.

Possible Aldol Reaction of Acetone

Acetone (\(CH_3COCH_3\)) can undergo self-condensation through an aldol reaction in the following manner:

The reaction described above shows that acetone (\(CH_3COCH_3\)) can undergo an aldol condensation with itself to produce both 4-Hydroxy-4-methylpentan-2-one and 4-Methylpent-3-en-2-one. Therefore, the correct starting material (compound 'A') that can produce these products through aldol condensation is acetone:option 1: \(CH_3COCH_3\).