I am performing a reaction in which I am adding ammonia in a solution containing acetyl chloride and my starting material. I get my final product with ammonium chloride. The final product is water soluble so it is not possible to isolate the product as a solid precipitate by adding water. Also the product is basic, but it is not precipitated in basic conditions. Can anyone suggest how to get the pure product?
Have you already tried to extract your compound with an organic solvent (DCM, ethyl acetate, etc.) from the basic water phase?
yes this is the best method, you'll try separation of compound with other organic solvent like ethyl acetate, chloroform, etc.
Sir, dont add water during reaction because it leads to acidity of the solution. Thats why u cant get your product. Ammonium chloride is weakly acidic so first of you should try to neutralize it by weak base. Concentration of base is responsible for formation of your prodct.
Ammonium Chloride can sublimate, so you can try separate your product from it by using sublimation in vacuum at slightly elevated temperature.
If the compound binds on reverse phase (C18 or CHP20), try loading it on a column (one can use loose material in a Buchner funnel), washing out the salt with water, and eluting the compound with methanol or acetonitrile. If you use loose reverse-phase media, note that it probably needs "activated" by washing with organic solvent (methanol or acetonitrile) followed by a water wash.
Dear Bernhard
I tried to extract my compound in ethyl acetate but it hardly go to the organic phase, because it is too water soluble. Please suggest something else.
Thanks
Dear Conrad,
Thanks for suggestion, my compound is soluble in Ethanol, I will try to check it in isopropanol actually it is a benzamidine so it may not go in isopropanol. And if it is soluble in ethanol, can I perform the swame thing as you mentioned earlier.
Please let me know
Thanks
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Dear Omprakash,
First distill off as many as acetyl chloride as u can under reduced pressure. this will considerably minimize the formation of ammonium chloride or acetamide in your reaction. Then you can neutralize with ammonia. You can even add some methanol before distillation as it will generate methyl acetate and HCl.
See what conditions work.
Regards,
Rajesh
For extraction you might add a small amount of methanol to the ethyl acetate to enhance the polarity.
If your compound possesses any functional groups another possibility would be the modification of your compound with suitable protecting groups which increase the hydrophobicity of your compound = simpler purification, and can be removed again easily giving your pure compound.
1.Check the boiling point of compound if possible distill it. Or 2. u can saturated water with NH4Cl and extract several times by MDC. 3.Can u avoid acetyl chloride? 4. Other inorganic base u can try.
In that case you can use methanolic ammonia instead of liquor ammonia for the reaction. Also let me know the way of water enter into the reaction mass.
Ammonium chloride has a high vapour pressure, maybe you product has less. Then you may use high vacuum for sublimation: http://pubs.acs.org/doi/abs/10.1021/ja01378a013
Dear Omprakash,
Try to perform the reaction in THF using Triethyl amine as a base. TEAHCl salt is insoluble in THF and it can be filtered. If at all your product is soluble in THF then no problem in recovering.
If not, try this purification method, dissolve your crude product in minimum amount of water and then add excess of acetone. may be you get a viscous liquid at the bottom.
Hope anyone process can help you.
Another option would be to sublime NH4Cl, if your compound is thermally stable
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