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Chemistry Question 65 – JEE-MAIN 2026

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In IUPAC nomenclature, the correct order of decreasing priority of functional group is :

IUPAC nomenclature assigns a specific priority order to functional groups, which is crucial for naming compounds with multiple functional groups.

Step 1: Recall IUPAC Functional Group Priority✦ Active

The standard decreasing priority order for the functional groups relevant to the given options is:

1. Ester (−COOR)

2. Amide (−CONH2)

3. Nitrile (−CN)

4. Aldehyde (−CHO)

5. Ketone (>C=O)

6. Alcohol (−OH)

7. Amine (−NH2)

8. Alkyne (−C≡C−)

Step 2: Evaluate each option based on the priority order○ Expand

Let's check each option against the established priority:

Option 1: −CONH2 (Amide) > >C=O (Ketone) > −CHO (Aldehyde) > −NH2 (Amine) > −C≡C− (Alkyne). Incorrect, as Aldehyde (−CHO) has higher priority than Ketone (>C=O). The correct order should be Amide > Aldehyde > Ketone.

Option 2: −CONH2 (Amide) > −COOCH3 (Ester) > −CHO (Aldehyde) > −NH2 (Amine) > −OH (Alcohol). Incorrect, as Ester (−COOCH3) has higher priority than Amide (−CONH2), and Alcohol (−OH) has higher priority than Amine (−NH2). The correct order should be Ester > Amide and Alcohol > Amine.

Option 3: −CONH2 (Amide) > −CHO (Aldehyde) > >C=O (Ketone) > −NH2 (Amine) > −C≡C− (Alkyne). This order is consistent with the IUPAC priority rules (Amide > Aldehyde > Ketone > Amine > Alkyne).

Option 4: −CONH2 (Amide) > −CHO (Aldehyde) > −CN (Nitrile) > −NH2 (Amine) > −C≡C− (Alkyne). Incorrect, as Nitrile (−CN) has higher priority than Aldehyde (−CHO). The correct order should be Amide > Nitrile > Aldehyde.

Step 3: Identify the correct option○ Expand

Based on the evaluation, Option 3 presents the functional groups in the correct decreasing order of priority according to IUPAC nomenclature.

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