Most Acidic Proton

[justin7w2011]

I always get these questions wrong. Is there a list or a good approach to these questions?

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[tuffnuts]

CARDIO
Charge- more negatively charged= more basic
Atom- the larger and more electronegative = more stable
Resonance
DI dipole induction
O orbitals. closer to nucleus = more stable. sp>sp3 for example

 

[justin7w2011]

I use that for ranking the acidity of an entire molecule but I am talking about finding which proton is most acidic when you are comparing multiple protons on the same molecule. Does cardio still work for that?

 

[matty675]

CARDIO can get a bit confusing when you are dealing with a very large organic molecule that contains multiple similar functional groups. I would recommend that you memorize the relative pKa's of all of the important functional groups, so that you are able to quickly answer those types of questions.

 

[tuffnuts]

yeah totally. for those kinds of problems you're going to usually be looking at dipole induction. like you'll have a molecule with an alcohol on one side, an oxo group and then a carboxylic acid and its asks you which H is the most acidic. in that case it would be the carboxylic acid proton because of the dipole induction/resonance of the two oxygens right there which is much more acidic than either an alpha proton or an alcohol proton.
Matty is right! you could learn the pka of those protons and that will for sure help you understand the concept. try to learn the pkas in the context of cardio and see the pattern

 

[bishbish777]

I typically try to just see which atom will be best able to stabilize a negative charge. In this context, you would see that a carboxylic acid F.G. is more acidic than, say, a phenol because the carboxylic acid can spread the negative charge between two electronegative oxygens.

 

[Daneosaurus]

I typically try to just see which atom will be best able to stabilize a negative charge. In this context, you would see that a carboxylic acid F.G. is more acidic than, say, a phenol because the carboxylic acid can spread the negative charge between two electronegative oxygens.

This is what I do too.