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6C.21b

Posted: Wed Dec 04, 2019 7:06 pm
by Joanne Kang 3I
Suggest an explanation for the different strengths of (b) acetic acid and formic acid.
Can someone please explain the answer to this? Thank u!

Re: 6C.21b

Posted: Wed Dec 04, 2019 8:00 pm
by Sears 4A
"Out of acetic acid and formic acid, formic acid is considered stronger because the CH3 in acetic acid is electron donating. The CH3 actually contributes electron density towards the O-H bond, making it harder to remove the H, and making acetic acid a weaker acid than formic acid."

Re: 6C.21b

Posted: Thu Dec 05, 2019 11:27 pm
by Drake Choi_1I
How can we tell that acetic acid is electron donating?

Re: 6C.21b

Posted: Fri Dec 06, 2019 3:18 am
by Hannah Lee 2F
If you draw out the Lewis structure, the main difference between the two groups is that acetic acid has a methyl group (CH3) where formic acid only has H. Thus, CH3COOH has an e- donating group, CH3, that destabilizes the negative charge of the resulting anion by contributing e- density. This means that the negative charge is less spread out over the anion (less delocalization), making it less stable, so that the H+ is less likely to be donated --> less acidic. Formic acid, on the other hand, does not have an e- donating group so the O-H bond is a little more polar (easier for the acidic hydrogen to be donated to H2O to form H3O+), making it more acidic overall.

Here's another explanation that is probably clearer: https://www.quora.com/Which-is-the-stro ... id-and-why