[spirochete]

Which is the more basic molecule: EtNH2 or MeCN?

My attempt: EtNH2 is more basic as the nitrogen is sp3 hybridised whereas the Nitrogen atom in MeCN is sp hydbirdized. This makes MeCN more acidic as the negative charge can be held closer to the nucleus.

Is this correct? is there any other reasons or logic?

Wow lots of replies with no answer! Yes, you're logic is correct. The increased s orbital character of the lone pair means that the nitrogen in MeCN is much less basic than the lone pair in an amine. Similar to comparing the basicity of HCC^- vs. the H₃CCH₂^-.

Also, the alpha hydrogen of MeCN is indeed somewhat acidic, similar to how the alpha hydrogen of carbonyl compounds are acidic. MeCN has a pKa of 25, compared to roughly 20 for acetone and 50+ for ethane.