Why is trichloroacetic acid stronger than acetic acid?

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JasmineChavez 1E
Posts: 29
Joined: Fri Sep 25, 2015 3:00 am

Why is trichloroacetic acid stronger than acetic acid?

Postby JasmineChavez 1E » Mon Nov 23, 2015 8:02 pm

I keep reviewing the video from last Wednesday's lecture but I still do not understand how it is stronger. If pKa=0.52 for tricholoro and pKa=4.75 for regular acetic acid how is it that the pKa is 10,000 times stronger? I see the trend that the larger the pKa the weaker the acid as it would be on the pH scale, but I still don't understand the explanation for the structures and why 3Cl makes the acid more stable

Sarah Noorani 3L
Posts: 30
Joined: Fri Sep 25, 2015 3:00 am

Re: Why is trichloroacetic acid stronger than acetic acid?

Postby Sarah Noorani 3L » Tue Nov 24, 2015 11:41 am

Since the Cl atoms in CCl4COOH are more electronegative than H atoms (in CH3COOH), they pull electron density away from the central carbon atom. This causes the carbon atom to pull electron density from the oxygen in the O-H bond, which weakens the O-H bond. Because the O-H bond is weaker in trichloroacetic acid than in acetic acid, it will more easily give off a proton, making trichloroacetic acid a stronger acid than acetic acid.


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