How to evaluate the basicity of molecules? (Ethanamide and Ethanamine, Example) [closed]








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Hi there i recently came in a position where was asked to evaluate the basicity of molecules, and managed to understand the heirachy of most molecules, however i couldn't figure out who was more basic between ethanamide and ethanamine, i thought if i look at which ever was more acidic it would mean it would be less basic. So i came to the conclusion that Ethanamide would be more acidic since it has ressonance and the negative charge would be distributed through the Nitrogen and Oxygen, so by definition ethanamine would be the most basic, if we look at the Lewis perpective of things since it has no ressonance it would donate a a pair of electrons more willingly.


However when i googled the pKa of both compounds i found that in reality Ethamine was more acidic, and I was mad, since it was more acidic it couldn't be the most basic out of the two. I found the pKa of Ethanamine to be 10,8 and Ethanamide to be 16,75.


How do i correctly evaluate the basicity of molecules, what are the variables to look out for? and what am i missing?


I further apologize for any errors, english is not my native language.
I also apologize for the long post. I get mad when i can't understand the logic behind something and I can't do anything else before I understand it :)




So, there are many factors that affect acidity or basicity of a compound, the main factors being bond electronegativities and resonance structures. However, I believe you are correct in assuming that those pKa values seem a bit off. Upon further investigation, I found that 10.8 is the pKa of the *conjugate acid* of ethanamine, so the pKa of the actual compound is much higher, making it the more basic of the two.


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