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+ Carboxylic acids
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Ole Henry Norback

What is the effect of an electron donating group on the acidity of carboxylic acid?

Dawn Parker  Follow

The electron withdrawing groups help stabilize the negatively charged carboxylate anion by helping to distribute the negative charge over more of the anion. This effect diminishes rapidly with distance from the carboxylate.

butyric acid pKa 4.81
4-chlorobutyric acid pKa 4.52
3-chlorobutyric acid pKa 4.06
2-chlorobutyric acid pKa 2.84

The more stable the carboxylate anion, the stronger acid is the carboxylic acid.

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Alexander Mathey  Follow

Electron withdrawing groups help stabilize the negatively charged carboxylate anion by helping to distribute the negative charge over more of the anion. The more stable the carboxylate anion, the stronger the acid.

This can be achieved through Inductive effect, which diminishes rapidly with distance from the carboxylate. Proximity and electronegativity influence the inductive effect. Resonance also influences acidity, thus, a carboxylic acid attached in close proximity to a Benzene group, will stabilize that anion charge nicely, and make it more acidic.

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