Identifying Electron-Donating Groups - Organic Chemistry

Card 1 of 8

0
Didn't Know
Knew It
0
1 of 87 left
Question

Electron donation and withdrawal have important impacts on acidity. What R group would yield the species with the highest pKa?

Q5

Tap to reveal answer

Answer

This question tests your knowledge about electron donation, as well as acidity. The question asks you to identify the species with the highest pKa, which means you need to look for the R group that will be the most donating. Electron donation will destabilize the conjugate base anion, localized partially on the oxygen of the hydroxyl moiety; the result is a less acidic acid, and a higher pKa.

Of the answer choices, three are electron-withdrawing. These include the nitro (-NO2), the ketone (-CCOMe), and the carboxyl (-COOH). The only answer choices that are electron-donating are the methyl (-Me), and the ether (-OMe). As the ether can push its lone pairs into the pi system of the ring and the carboxyl group, it is the stronger electron-donating group. The methyl can only donate electrons through inductive effects, or electronic polarization of sigma bonds, which is not as strong of an electron donation effect. Thus, -OMe is the correct answer.

← Didn't Know|Knew It →