Strength of Carboxylic Acids

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FDeCastro_1B
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Strength of Carboxylic Acids

Postby FDeCastro_1B » Thu Dec 05, 2019 4:14 pm

Can someone please explain how to go about answering this:

List the following carboxylic acids in order of increasing strength: CHCl2COOH, CH3COOH, and CH2ClCOOH.

Chem_Mod
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Re: Strength of Carboxylic Acids

Postby Chem_Mod » Thu Dec 05, 2019 6:18 pm

This is about stability, and more specifically, inductive effects.

When your acid is deprotonated, your molecule will have a negative charge. The molecule will be more stable if the negative charge is more "distributed" around the molecule. The way to better distribute/share that negative charge is through induction, where an electronegative atom draws the negative density toward itself. Chlorine is very electronegative, so it would make the resulting negatively charged molecule more stable. The resulting conjugate base is more stable, so the molecule with more chlorines is willing to lose its hydrogen. Therefore, CH2Cl2COOH is most acidic.


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