Adding an electron withdrawing group to alpha carbon? (acid-base q)

[kstreet]

Quick question that I came across.

Say you have C-COOH, and you add an electron withdrawing group to the alpha carbon...

Does this increase or decrease the acidity of the hydrogen?

Would the added EWG cause the conjugate base to be destabilized making it less acidic, or does it increase the acidity by making the OH bond more polar?

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[Richter915]

Here's my take...Adding an EWG will make your COOH group MORE acidic. If you imagine your COO- group after deprotonation...it's electron rich ya? So if you have an EWG attached to your alpha carbon...it literally "sucks" some of the electron density closer to it. If you had an EWG with the acidic proton staying on the COOH group, the proton is just another atom which takes electron density away from your EWG.

So yes, your EWG makes your proton more acidic.

 

[EECStoMed]

Quick question that I came across.

Say you have C-COOH, and you add an electron withdrawing group to the alpha carbon...

Does this increase or decrease the acidity of the hydrogen?

Would the added EWG cause the conjugate base to be destabilized making it less acidic, or does it increase the acidity by making the OH bond more polar?

It most definitely INCREASES the acidity of the alpha hydrogen. The more electron withdrawing groups there are, the more acidic the hydrogen. It makes the conjugate base more stable by sharing in on the lone pair of electrons. Hence, making it less negative so to speak and thus more stable. It's called inductance. It's also the reason why water is more acidic than say methanol, because once the hydrogen is lost, you want a more electro negative atom of a less electron donating group to stabilize the conjugate base.

 

[AppleseedCast]

it becamse crazzzzyyyyyy more acidic since the conjugate base becomes stabilized because the lone pair can be delocalized via induction or resonance depending on the ewg that you are using