Carbonyl Reactivity

Question

Relative electrophilicity: acid chloride > aldehyde > ketone > amide because:

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1. **Definition**: Electrophilicity is the 'thirst' of the carbonyl Carbon for electrons. It increases if the carbon has a higher partial positive charge ($\delta^+$).
2. **Acid Chlorides**: Chlorine is highly electronegative ($-I$ effect) which pulls density away. While it has lone pairs, its $\pi$-donation (resonance) is weak due to poor orbital overlap between $3p$ ($Cl$) and $2p$ ($C$). Result: Very high $\delta^+$.
3. **Aldehydes vs Ketones**: Alkyl groups are electron-donating ($+I$). Ketones have two such groups, while aldehydes have one. This makes the ketone Carbon less positive and also more sterically hindered.
4. **Amides**: The Nitrogen atom has a lone pair that strongly donates into the carbonyl via resonance ($N^+=C-O^-$). This significantly 'fills' the $\delta^+$ on Carbon.
5. **Summary Order**: **Acid Chloride > Aldehyde > Ketone > Amide**.

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Carbonyl Reactivity

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