Acid Strength- Acetic vs Formic Acid

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CNourian2H
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Joined: Fri Aug 30, 2019 12:16 am

Acid Strength- Acetic vs Formic Acid

Postby CNourian2H » Fri Dec 06, 2019 6:04 pm

Problem 6C.21b: Why is formic acid stronger than acetic acid? I'm confused with the electronegativity/polarity aspect of it.

Ryan 1K
Posts: 101
Joined: Fri Aug 09, 2019 12:15 am

Re: Acid Strength- Acetic vs Formic Acid

Postby Ryan 1K » Sat Dec 07, 2019 12:43 am

The acetic acid has a methyl group attached (CH3), which is an electron-donating compound. As such, the anionic form of the acetic acid is less stable since the CH3 does not delocalize the negative charge and instead adds to it. Meanwhile, the H atom attached to the formic acid is electron-withdrawing, and it stabilizes the product of the acid-base reaction by delocalizing the electron densities, so the forward reaction will be more favorable and the formic acid will more readily give away a proton.

ATingin_3I
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Joined: Fri Aug 30, 2019 12:17 am

Re: Acid Strength- Acetic vs Formic Acid

Postby ATingin_3I » Sun Dec 08, 2019 1:48 am

Ryan Chew 1C wrote:The acetic acid has a methyl group attached (CH3), which is an electron-donating compound. As such, the anionic form of the acetic acid is less stable since the CH3 does not delocalize the negative charge and instead adds to it. Meanwhile, the H atom attached to the formic acid is electron-withdrawing, and it stabilizes the product of the acid-base reaction by delocalizing the electron densities, so the forward reaction will be more favorable and the formic acid will more readily give away a proton.


so formic acid is more acidic because the conjugate base is more stable?

CNourian2H
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

Re: Acid Strength- Acetic vs Formic Acid

Postby CNourian2H » Sun Dec 08, 2019 3:39 am

Oh I think I got it. It's because of the CH3 in acetic acid is electron donating, and it contributes e- density towards the O-H bond making the bond stronger to break and H+ ion less wanting to go and attach to another compound.

CNourian2H
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

Re: Acid Strength- Acetic vs Formic Acid

Postby CNourian2H » Sun Dec 08, 2019 3:40 am

So it is involving electronegativity...Im guessing.


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