Ochem questions..

[AASDDS1]

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a question from an old ADA exam..

which compound is soluble in aqueous HCL but separates when excess NaOH is added?
the answer was an amine..
i thought it would be a carboxylic acid, because likes are soluble in likes (acid in acid) and co2h is separated with Na0H. not sure if i'm not understanding the question? It's late so i may be having a huge brain fart right now :/

thanks !

 

[AlbinoPolarBear]

a question from an old ADA exam..

which compound is soluble in aqueous HCL but separates when excess NaOH is added?
the answer was an amine..
i thought it would be a carboxylic acid, because likes are soluble in likes (acid in acid) and co2h is separated with Na0H. not sure if i'm not understanding the question? It's late so i may be having a huge brain fart right now :/

thanks !

Pay attention to which phase the compounds with be in.
Remember, the formal charges will make the compound more soluble in aqueous as the polarity of the water molecules will stabilize those charges.

Let's start with carboxylic acids:
RCOO- (soluble in aqueous) <--> RCOOH (soluble in organic layer)

Amines:
RNH3+ (soluble in aqueous) <--> RNH2 (soluble in organic)

So it was soluble in Aqueous HCl, and when you add a base (take away proton), it will be soluble in organic.

From the equations above, the amines would fit. The amine would originally be soluble in aqueous HCl, but if you add a base, it will remove that proton, making it soluble in the organic layer.

If you started out with RCOO-, and you add base to the solution, it will still remain in the RCOO- form, therefore you wouldn't be able to separate it to the organic layer.

Hope this helps!