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How does a methyl group affect the acidity of acetic acid?
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carboxylic acid
Alcohols may be oxidized to give aldehydes, ketones, and carboxylic acids. The oxidation of organic compounds generally increases the number of bonds from carbon to oxygen, and it may decrease the number of bonds to hydrogen.
The methyl group (βCHβ) acts as an electron-donating group, which decreases the acidity of acetic acid compared to formic acid.1
In carboxylic acids, acidity is determined by the stability of the resulting carboxylate ion. Electron-withdrawing groups increase acidity by stabilizing the negative charge on the carboxylate ion, whereas electron-donating groups like the methyl group destabilize the ion by increasing electron density. Because the methyl group donates electrons, it makes acetic acid approximately 10 times weaker as an acid than formic acid, which contains only a hydrogen atom in that position.1