Which of the following compounds is least acidic?

Question

Quizplus · Accepted Answer

The acidity of a compound depends on the stability of the conjugate base formed after losing a proton. In this case, compound I has the most electronegative atom (fluorine) bonded to the carbon adjacent to the carbonyl group. This causes the negative charge to be localized on the oxygen atom of the conjugate base, making it a stable anion. On the other hand, compound V has a positively charged nitrogen in its conjugate base, which makes it highly unstable and therefore the most acidic. The other compounds fall in between, but compound III has a resonance structure that stabilizes the negative charge on the oxygen atom, making it slightly more acidic than compounds II and IV.

Which of the Following Compounds Is Least Acidic