Why would the alpha hydrogen on a aldehyde be more acidic then the h attatched to the carbonyl group? The h on the carbonyl group is closer to an electron withdrawing group correct?
acidity of aldehyde alpha hydrogen
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Firstly, when you say carbonyl, note that it can either be a ketone or an aldehyde. So I think you're trying to ask why the hydrogen from the aldehyde is more acidic than the ketone?
The only difference between these is that the aldehyde has a hydrogen attached, while the ketone has an alkyl group attached. In general, alkyl groups offer less stability the anions as opposed to Hydrogens (The opposite is also true: for cations, the alkyl groups stabilize the cations). Thus, the anion formed from the ketone is less stable than that of the aldehyde, meaning that the ketone is not as acidic (Greater pH, greater pKa).
The only difference between these is that the aldehyde has a hydrogen attached, while the ketone has an alkyl group attached. In general, alkyl groups offer less stability the anions as opposed to Hydrogens (The opposite is also true: for cations, the alkyl groups stabilize the cations). Thus, the anion formed from the ketone is less stable than that of the aldehyde, meaning that the ketone is not as acidic (Greater pH, greater pKa).
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It is because of the stability of the conjugate base.
If you look at the structure of the deprotonated form of the aldehyde you can draw a resonance structure where the double bond is between the alpha carbon and carbonyl carbon. There will also be a negative charge on the oxygen in this structure.
The resonance stability is not seen when you remove the hydrogen from the carbonyl carbon
If you look at the structure of the deprotonated form of the aldehyde you can draw a resonance structure where the double bond is between the alpha carbon and carbonyl carbon. There will also be a negative charge on the oxygen in this structure.
The resonance stability is not seen when you remove the hydrogen from the carbonyl carbon
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In this case, yes. In general, the more stable the conjugate base is, the more acidic the acid will be. That being said, in this scenario you are comparing the stability that is due to the withdrawing group vs the stability brought about by resonance. When comparing the two, resonance is indeed more important.
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