What is the order of increasing acidic strength of the following compounds?

Question

Is this question supposed to be solved on the basis of s character or will I also have to check for stability of conjugate base using resonance and inductive effect? I'm quite confused. Please tell me the correct order for both the questions and also how to do it.

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Answer 1 · 2018-04-23T23:33:09

All of those factors matter!

The acidity of these protons depends on the stability of the conjugate base, having been deprotonated:

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Clearly #(1)# is least acidic; nitrogen is not very electronegative compared to oxygen in #(5)#.

However, in increasing order #(2)#, and #(3)# are more acidic, due to the hybridization of the nitrogen atom.

Lastly, #(4)# is most acidic, because that oxygen is very happy with all of that electron density.