# Why are amides weaker acids than water?

Based on a a recent question I asked on ChemSE, the answer to my question was that amides are weaker acids than water with a typical pKa value of ~20. Although, this answers my question, it got me wondering why amides are weaker acids than water. After deprotonation, the negative charge formed on the amide is delocalized by resonance and on two electronegative atoms (N & O). After deprotonation in water, the negative charge is localized on a single electronegative atom (O). So why are amides weaker acids than water? Is it linked to the fact that, on average , the negative charge is on a more electronegative atom in OH- than it is in the conjugate base of amide? Isn't resonance delocalization a bigger factor?

• Consider that even if amides are very weak acids, they are much stronger acids than ammonia. Jun 10 at 12:42
• How is ammonia relevant to amides? An amide is in one formal way just ammonia with 1 H substituted by acyl. $\ce{H-NH2}$ versus $\ce{H-NH-CO-R}$ Jun 10 at 12:51