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The ketone carbonyl group is less reactive to nucleophilic attack than aldehyde since the alkyl group in ketone is electron-donating towards the carbon.

Is this the same case for benzophenone, where there is a phenyl group?

Phenyl groups are usually electron-withdrawing, but in the case of benzophenone, would it be electron-donating through resonance?

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  • $\begingroup$ Carbonyl group are electron withdrawing for a benzene ring. So by converse, phenyl group is electron donation for carbonyl group. $\endgroup$
    – Groverkss
    Commented May 19, 2019 at 13:08

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A keto or an aldo group with phenyl ring is less reactive towards nucleophillic addition then their aliphatic counterparts(acetaldehyde or acetone).With phenyl group the positive charge on carbonyl carbon is delocalised via resonance (structures 2 , 3 , 4 , 5 ) .

enter image description here Resonance with phenyl ring is due to conjugation.

enter image description here such conjugation is absent in aliphatic aldehydes and ketones.Therefore carbonyl compounds with phenyl rings bonded to carbonyl group are less reactive then their aliphatic counterparts.

With respect to + carbon on carbonyl group pi electrons on phenyl group are polarized towards it , in a way electron donating .

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