Question:

Which is not true about acetophenone ?

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Acetophenone falls under the category of ketones. It does not have hydrogens attached to the carbonyl carbon.

Updated On: May 26, 2024

Reacts with 2,4-dinitrophenyl hydrazine to form 2,4-dinitrophenyl hydrazone
Reacts with Tollens reagent to form silver mirror
Reacts with I₂/ NaOH to form iodoform
On oxidation with alkaline KMnO₄ followed by hydrolysis gives benzoic acid

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The Correct Option is B

Solution and Explanation

Acetophenone is a ketone and does not react with Tollen's reagent to give silver mirror. Acetophenone has the molecular formula C₈H₈O with a ketone functional group. The structure of ketone is as follows:

Tollen's Test is used for aldehydes or compounds that have a hydrogen atom attached to the carbonyl carbon. However, acetophenone does not have any such hydrogen atom attached to a carbonyl carbon like the case of aldehydes. Hence, Acetophenone does not give a silver mirror with Tollen's reagent.

For the other options:

Acetophenone reacts with 2,4-Dinitrophenylhydrazine to form 2,4-Dinitrophenylhydrazone. The reaction is given as:
Acetophenone gives a yellow precipitate with NaOH.
Acetophenone on oxidation with KMnO₄ causes breaking or rupture of C-C bond and thus forms benzoic acid.

Also Read: Tests for Aldehydes & Ketones

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Notes on Aldehydes, Ketones and Carboxylic Acids

Concepts Used:

Aldehydes, Ketones, and Carboxylic Acids

Aldehydes, Ketones, and Carboxylic Acids are carbonyl compounds that contain a carbon-oxygen double bond. These organic compounds are very important in the field of organic chemistry and also have many industrial applications.

Aldehydes:

Aldehydes are organic compounds that have the functional group -CHO.

Preparation of Aldehydes

Acid chlorides are reduced to aldehydes with hydrogen in the presence of palladium catalyst spread on barium sulfate.

Ketones:

Ketones are organic compounds that have the functional group C=O and the structure R-(C=O)-R’.

Preparation of Ketones

Acid chlorides on reaction with dialkyl cadmium produce ketones. Dialkyl cadmium themselves are prepared from Grignard reagents.

Carboxylic Acid:

Carboxylic acids are organic compounds that contain a (C=O)OH group attached to an R group (where R refers to the remaining part of the molecule).

Preparation of Carboxylic Acids

Primary alcohols are readily oxidized to carboxylic acids with common oxidizing agents such as potassium permanganate in neutral acidic or alkaline media or by potassium dichromate and chromium trioxide in acidic media.