Solubility help!

[Homoochan]

one of the solution from AAMC question says:

amine and carboxylic acid are soluble in dilute acid and base while amide and nitro-compounds are not.

Why are amine and carboxylic acid soluble in dilute acid and base?
If amine is a weak base, it should have low tendency to gain H, and dilute acid should have low tendency to donate H. How can amine soluble then?

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[macmini]

Ok here is what I am thinking I am open to any other ideas. Solubility just has to do with intermolecular forces like h-bonding, Vander waals, dipole, and momentary dipole. So here goes......Any acid or base is obviously charged and can form h-bond with other compounds. That is why a carboxylic acid is more soluble in aqueous solutions than it corresponding alkane or the less oxidized aldehyde. So a carboxylic is soluble in a week acid or base as it can h-bond. So can an amine for h-bonds with the nitrogen in mostly primary and secondary amines.
Now we can go on to amides they act like tertiary amine and can not donate any h-bonds and can only accept them. The polar carbonyl is less polar due to resonance with the nitrogen and forms a partial shared double bond with the nitrogen and carbonyl. Again both of these groups can only accept h-bonds and cannot donate such. Making amines more soluble than its corresponding alkane but much less soluble than the corresponding acid or alcohol.

 

[GCT]

one of the solution from AAMC question says:

amine and carboxylic acid are soluble in dilute acid and base while amide and nitro-compounds are not.

Why are amine and carboxylic acid soluble in dilute acid and base?
If amine is a weak base, it should have low tendency to gain H, and dilute acid should have low tendency to donate H. How can amine soluble then?

Consider amino acids - dilute base solution deprotonates the carboxylic acid and and dilute acid solution can protonate the amine - whenever you have a relative base and acid the acid is going to protonate the base.