0Class 12 Chemistry – Structures of Aldehydes, Ketones, and Carboxylic Acids
1. Aldehydes
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Functional Group: –CHO
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Structure Concept:
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Carbonyl group (C=O) is at the end of the carbon chain.
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One hydrogen atom is attached to the carbonyl carbon.
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Example Visualization:
H | C – C – … (rest of chain) || O -
Carbonyl carbon is terminal, hydrogen is attached, making it aldehyde.
2. Ketones
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Functional Group: –CO–
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Structure Concept:
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Carbonyl group (C=O) is within the carbon chain, not at the end.
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Two carbon atoms are attached to the carbonyl carbon.
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Example Visualization:
C – C – C – … (rest of chain) || O -
Carbonyl carbon is internal, connected to two carbons, forming a ketone.
3. Carboxylic Acids
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Functional Group: –COOH
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Structure Concept:
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Contains a carbonyl group (C=O) attached to a hydroxyl group (–OH).
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The carboxyl carbon is usually at the end of the carbon chain.
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Example Visualization:
O || C – OH | C – … (rest of chain) -
Carbonyl carbon is terminal, hydroxyl attached, forming a carboxylic acid.
4. Quick Comparison
| Compound Type | Functional Group | Position of C=O | Key Feature |
|---|---|---|---|
| Aldehyde | –CHO | Terminal | Carbonyl carbon has H |
| Ketone | –CO– | Internal | Carbonyl carbon bonded to 2 C |
| Carboxylic Acid | –COOH | Terminal | Carbonyl + Hydroxyl |
These visualizations make it easy to distinguish:
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Aldehyde: carbonyl at the end, H attached
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Ketone: carbonyl inside, bonded to carbons
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Carboxylic acid: carbonyl + hydroxyl, acidic nature
