Solubility of Functional Groups in acids and bases?

[screamingpumpki]

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What are the solubilities of functional groups in both acids and bases? This is what I do know:

carboxylic acids: soluble in acids and bases
amides and nitro groups: not soluble in acids and bases
amines: soluble in acids and bases

So I guess that leaves ethers, esters, and alcohols.

What determines solubilities in acids and bases? I know "like dissolves like" so polar in polar and nonpolar in nonpolar. But I ran across this in a practice MCAT test and I didn't know we had to know the solubilities of functional groups in acids/bases. And I can't find a list anywhere. Is this something I should just memorize?

Thanks.

 

[ChemTutor]

Those are odd looking solubility rules. Where did you find them?

When looking at solubility you need to look at the solvent type (e.g. H2O: polar, forms H-bonds vs hexane: non-polar, not capable of H-bonding) and the solute type to weight contributions of different factors. Often it is not clear-cut if a given molecule is more "like" this solvent or that one.

For example, phenol is slightly soluble in water due to H-bonding, but it is much more soluble in hexane.
But if we add some base (NaOH) converting phenol to PhO-, then phenol (the phenolate anion) will be very soluble in H2O, but not soluble in hexane.

 

[screamingpumpki]

The solubility "rules" that I found were the explanation to an answer from a practice AAMC MCAT test. :/

I can't even find a list on google or in my princeton review books. Is there a list?

Thank you for your explanation - it helps.

 

[JLeBling]

Found on AAMC 4. I got this one wrong too. I've looked all over the SDN forums and I cannot find an answer that makes half decent sense. So here is my take on it, though I don't know if it's correct:

We know that amides are less basic than amines, because the oxygen of the carbonyl group withdraws the lone pair of electrons away from the nitrogen, like so:

Without the free lone pair, and removed of its basicity, the amide cannot be protonated in a weak acid.

Carboxylic acid is soluble in dilute base, because when the pH>pKa, the carboxylic acid deprotonates resulting in a negative charge which increases its solubility in a polar protic solvent.

Amine is soluble in dilute acid, because when pH<pKa, the amine protonates gaining a positive charge which increases its solubility in a polar protic solvent.


That is my best guess...