i have synthesized an amide compound from Amine and carboxylic combination, im facing problems in seperating amide from free amines,the problem is both amide and amines are soluble in water, if anybody have a solution for my problem kindly comment below
Many thanks
you can control amine during reaction using slightly less amine than required for the reaction.You should have to optimize the reaction condition.
Also you can go for salt preparation of amine in organic solvent as properties changes you can purify your mixture easily.
Depending on the scale of your experiment, you might resort to reverse phase chromatography/HPLC/C-18. Sometimes regular phase chromatography will also work for separating amide from amine, especially if you submit your mixture after acidifying it (amine will be converted to a salt, which is very polar and stays on top of Si-gel column). A polar solvent may have to be used to elute the amide from such column.
Instead of chromatographic methods, sometimes crystallization approaches work, especially that it sounds like your compound(s) are very polar. For this purpose I would concentrate the mixture in water to a very concentrated solution, add some acid (preferentially HCl or HBr if your compound is stable under these conditions, but other acid can alos be used, like camphorsulfonic or even tartaric) and then, with stirring, add a water-miscible solvent that precipitates the amine salt (e.g. isopropanol, ethanol, THF or the like). That way your amide might stay in solution, amine salt is precipitated - filter the solids, concentrate the solution, etc.
Good luck!
It would be good to know what the product and reaction conditions are. What solvent is used? Assuming that the product does not have other amine functionality and is soluble in the reaction solvent, the mixture (or aqueous solution) could be stirred with an acidic resin ( e.g. dowex 50) or filtered through a column of the same. If this works there would be no need to resort to less straightforward alternatives. I
Add enough acid so that the amine is fully protonated, then separate using a separatory funnel with an adequate inmiscible solvent such as ether or ethyl acetate. The protonated amine should stay in aqueous solution, altho I'd have to see the specific compounds to say if this method would work.
Tomas,
Both his compounds are soluble in water, if I understood the OP correctly.
Jacek
Thank you all for your valuable suggestions, I have seen in a article they mentioned dioxane with benzene combination could able to separate amide , ist possible???
you can use acidic, ion-exchange resin (e.g. Dovex or Ambelyst) to selectively remove amine from solution.
it depends on your product. if it is amides of amino acids, just do column to get your product because adding acid will deblock the product.
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