[Serenagreene]

I have a mixture of 3 unknown compounds.  The mixture is liquid, but I know that I have 2 liquids and 1 solid.

1st - dissolved mixture in Hexane:EtoAc and extracted with water
        Aqueous Layer - 1 compound (mini-polor and multi-polar compound)  I have   
        this compound almost pure it is one of my liquids.
        Organic Layer - 2 compounds
2nd - to the Organic Layer extracted with diute HCl
        Aqueous Layer - 1 compound (Non-water soluble amine, green liquid, BP ~86,
                               UV Active)
        Organic Layer - 1 compound - can't distill as it elutes of with the solvent.
3rd - to the Organic Layer added aqueous NaHCO3
        Organic Layer - nothing
        Aqueous Layer - 1 compound THIS IS WHERE I START HAVING PROBLEMS
        Added HCl - expected a precipitant to form (There was a lot of bubbles released). Nope.... so I thought I would try to get it into an ether layer.  Well some of it went into the ether layer, but most remained in the aqueous layer (TLC dot was a lot darker for the aqueous layer compared to the the ether layer.)  I'm confused as to why it won't leave the aqueous layer especially since it was non-water soluble to begin with.  Any suggestions?


-Serena

[agrobert]

Did you check the pH of your aqueous layer? Do you know what the bubbles that were produced are?

[Serenagreene]

No didn't think to check the pH. I will do that Monday.  But I have a really bad feeling that the bubbles were CO2 from my carboxylic acid. 

I've been doing a little more research and I came across something that mententioned the Alkylamine and non-water soluble caboxylicacids are incompatible?  Why is that?

-Serena

[Serenagreene]

On second thought the CO2 didn't come from my Carboxylic acid, but from

NaHCO3 + HCl -->  NaCl + H20 + CO2

I feel a little better now.

-Serena

[ARGOS++]

Dear Serenagreene,


Before you fear!, think about what HCl will do with NaHCO3 that may be in excess.
It’s nothing to worry about.

I’m pretty sure all other you will find out.

Good Luck!
                   ARGOS⁺⁺

[agrobert]

Good.  Now you understand where the bubbles are from.
It is always important to check your pH when doing an extraction to make sure you have completely reprotonated all of your carboxylic acid.  Don't worry.

[barcrphd]

"Organic Layer - 1 compound - can't distill as it elutes of with the solvent.
3rd - to the Organic Layer added aqueous NaHCO3
        Organic Layer - nothing
        Aqueous Layer - 1 compound THIS IS WHERE I START HAVING PROBLEMS
        Added HCl - expected a precipitant to form (There was a lot of bubbles released). Nope.... so I thought I would try to get it into an ether layer.  Well some of it went into the ether layer, but most remained in the aqueous layer (TLC dot was a lot darker for the aqueous layer compared to the the ether layer.)  I'm confused as to why it won't leave the aqueous layer especially since it was non-water soluble to begin with.  Any suggestions?"

Your said u have two liquids and one solid. so in the third and final step you should have a solid right? and what do you mean by "you cannot distill as it elutes off with the solvent"? you mean distills off? what do you get after evaporating the ether layer? a solid? if your third compound is really a solid then you can removed water under vaccuum and then recrystalize to get pure compound.

[gaiety]

You must make sure you have acidified the fianl aqueous layer to pH 5-1 with a cold bath gradually. Then if the pricipitant don't form and you can't extract it with organic solvents either, I think you do step 3 just because you wanna purify the carboxylic acid via transforming acid and base. If you'd like to convert the crude carboxylic acid obtained after step 2 into corresponding ester and then purify the ester! Then you can hydrolyze the pure ester to target acid. Maybe that is a long shot, but it is worth to try.