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Chemistry Question 67 – JEE-MAIN 2025

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Which among the following compounds give yellow solid when reacted with NaOI/NaOH ? (A) CH3−CH(OH)−C2H5 (B) CH3−CH2−CH2−OH (C) CH3−C(=O)−C2H5 (D) CH3−C(=O)−OH (E) CH3−CH2−C(=O)−H Choose the correct answer from the options given below :

Identify the specific named reaction indicated by the reagents NaOI/NaOH and the formation of a yellow solid.

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Ninja Strategy•Functional Group Scan

Quickly identify compounds with methyl ketone (CH3CO−) or methyl carbinol (CH3CH(OH)−) groups, as these are the only ones that give a positive iodoform test.

Step 1: Identify the Reaction and Reagents✦ Active

The reaction with NaOI/NaOH (which generates I2 in NaOH) and the formation of a yellow solid (CHI3) is characteristic of the iodoform test.

Step 2: Recall Criteria for Iodoform Test○ Expand

Compounds that give a positive iodoform test must contain either a methyl ketone (CH3CO−) group or a methyl carbinol (CH3CH(OH)−) group. The methyl carbinol group is oxidized to a methyl ketone under the reaction conditions.

Step 3: Analyze Each Compound○ Expand

(A) CH3−CH(OH)−C2H5 (Butan-2-ol): Contains a CH3CH(OH)− group. Positive test. (B) CH3−CH2−CH2−OH (Propan-1-ol): Does not contain the required group. Negative test. (C) CH3−C(=O)−C2H5 (Butan-2-one): Contains a CH3CO− group. Positive test. (D) CH3−C(=O)−OH (Ethanoic acid): Carboxylic acid, does not give the test. Negative test. (E) CH3−CH2−C(=O)−H (Propanal): Aldehyde, does not contain a CH3CO− group (only acetaldehyde, CH3CHO, gives a positive test among aldehydes). Negative test. Therefore, only (A) and (C) give a positive iodoform test.

💡 Teacher's Secret Hint

Remember that carboxylic acids and their derivatives generally do not undergo the iodoform reaction, despite having a CH3CO− moiety.

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