Primary Amide - Acidity Question

[drechie]

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A really simple question that I havent found a clear answer to: why isnt the Hydrogen bonded to the Nitrogen in this example acidic? And why would the H of a carboxylic acid be acidic? They both have resonance structures....

 

[Cawolf]

The N is sp2 hybridized, and protons in sp2 orbitals are held closer to the central atom, increasing the BDE, and making them less acidic.

The O in an acid is sp3 hybridized, and protons in sp3 orbitals can be acidic. In particular when they are bound to a heteroatom.

 

[rtmsf95]

You can also look at electronegativity. The more electronegative an atom, the better it will be able to capture/hold and stabilize that excess negative charge that is present in the conjugate base. 2 oxygens would be extremely acidic. Nitrogen isn't as electeonegative, and so an amide won't be as acidic as a carboxylic acid.

 

[OrdinaryDO]

You can also look at electronegativity. The more electronegative an atom, the better it will be able to capture/hold and stabilize that excess negative charge that is present in the conjugate base. 2 oxygens would be extremely acidic. Nitrogen isn't as electeonegative, and so an amide won't be as acidic as a carboxylic acid.

Nailed it. The two oxygen atoms in the functional group of CA would form a much more stable resonance structure than an Amide functional group.