Concept:Nucleophilic addition relies on the accessibility and electrophilicity (positive charge) of the carbonyl carbon. Aromatic rings decrease reactivity via electron-donating resonance (+R effect) and massive steric hindrance.
Solution:- Benzaldehyde (\( C_6H_5-CHO \)): An aldehyde. It has one bulky phenyl group, but the other side is just a tiny hydrogen atom. Aldehydes are inherently more reactive than ketones.
- Acetophenone (\( C_6H_5-CO-CH_3 \)): An aromatic ketone. It has one bulky phenyl group and one methyl group. The methyl group adds steric bulk and donates electron density (+I), lowering reactivity.
- Benzophenone (\( C_6H_5-CO-C_6H_5 \)): A diaromatic ketone. It is severely sterically hindered by two massive phenyl rings, which also aggressively delocalize the positive charge away from the carbonyl carbon via resonance. It is the least reactive.
- Thus, the decreasing order is: Benzaldehyde > Acetophenone > Benzophenone.
Why other options are incorrect:Any order placing a ketone ahead of an aldehyde (Options B, C) is incorrect. Option A incorrectly lists benzophenone as more reactive than acetophenone.
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