Organic Acidic basic question

[SmileDesignersDDS]

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How do you know which organic reaction is the most acidic and the most basic?
What are the general rules?
I saw a destroyer question where a carboxylic acid had a positive charge on the OH and that was the most acidic?
Please help this topic is killing me!!!!!

 

[apollo69]

Take off the most acidic hydrogen and evaluate the stability of the deprotonated molecule.
Remember, acids are proton donors. Therefore, the most acidic molecule is the one that is most happy with losing a proton so the more stable the deprotonated molecule, the more acidic it is.

 

[SmileDesignersDDS]

Well how do you know the stability of the de-protonated molecule?

 

[apollo69]

You can assess the stability by looking at whether the deprotonated molecule has resonance structures or becomes aromatic. Both will increase stability. Also, for molecules without resonance, if there is an electronegative atom somewhere on the molecule, it will pull the electrons away from the protons, which also increases acidity.
If all else fails, try to remember this order of decreasing acidity:
Carboxylic acid>alcohols>ketones/aldehydes>esters>alkynes>alkenes>alkanes

 

[SmileDesignersDDS]

What about charge?