AL CHEM acid base extraction

1.
ethyl ethanoate is relatively insoluble in water.
hexan-1-amine neither; but it's converted to an ionic salt (alkyl-ammonium cation) after protonation, which is becomes soluble.

now, with an aqueous layer and a less polar solvent layer, the protonated amine remains in the aqueous layer while ethyl ethanoate is extracted into the ether layer.

in other words, ether is NOT to extract the amine; it's to extract (remove) the ethyl ethanoate.


2.
amine could be soluble but look at the number of carbon. Six. it couldn't be very soluble; it behaves as a polar organic compound, like what ethyl ethanoate does.

therefore, before adding acid, both amine and ethyl ethanoate behave similarly, could not be extracted at ease.

to solve this, one can utilize the difference in chemical properties: by some means, make one of them to behave differently, like solubility in another solvent. the process is preferrably reversible, such that you can recover the extracted compound.

(e.g. you can alkylate the amine with iodoalkane to give tetraalkylammonium ion, which should also be more soluble in polar solvent;
yet you cannot recover the amine after extraction.)


2011-12-05 18:37:32 補充：
3.
after the ethanoate is removed by ether, the amine exists in form of protonated ammonium salt.
WHAT we want is amine, not the salt; so we've to convert the ion back into un-protonated amine.

2011-12-05 18:37:55 補充：
even the amine isn't very soluble, extracting with ether can concentrate the amine as well as easier recovery (ether is more volatile).

2011-12-08 19:03:44 補充：
no, amine should turn into free base after addition of NaOH.
the free amine should be slightly soluble -- dissolves in some extent, not too much.