I synthesized the pyrimidine carboxylic acid in acetic acid as solvent and catalyst but after putting the reaction mixture into ice it does not solidify then I used the solvent extraction with ethyl acetate to separate my product. I removed all the water but still even at rotary evaporator it still not solidify due to trapping of acetic acid. I tried solvent extraction again and again but did not work.
Предварительно уксусную кислоту отгоняйте. Пиримидин-2-карбоновая кислота (т.пл.182-185 градус по цельсию) ) хорошо растворим в этаноле, поэтому экстрагируйте этим растворителем и затем кристаллизуйте!
Reflux your pyramiding-2-carboxylic acid in strictly anhydrous methanol (freshly distilled from magnesium or freshly opened bottle). Monitor by TLC to be sure methyl pyrimidine-2-carboxylate is not forming. It may take an hour or more of reflux. Test for completion by removing approx. one mL per hour and evaporating. If evaporation gives crystals, evaporate the whole reaction mixture. Acetic acid readily forms methyl acetate. When you evaporate the methanol, methyl acetate will evaporate also. Pure pyrimidine-2-carboxylic acid should be left behind. If what’s left behind is methyl ester of product, find a procedure for lithium hydroxide hydrolysis of methyl esters to recover the free acid. LiOH monohydrate in an aqueous ethereal solvent is so mild your product should survive. Other hydroxides may cause the pyrimidine ring to open. Best wishes.
Irfan:
Remove the acetic acid by high vacuum or/and co-evaporated with water multi-times.
If you are just working on a small scale, you could concentrate your reaction mixture and then blow nitrogen accords the isolated oil. Acetic acid has an interesting property - if you can smell it, it is still in your sample. Drying under a nitrogen stream is a way to purge it from your isolate. Maybe (if you are lucky) the remaining pyridine acid will crystallize when you get the acetic acid out of it.
For a large quantity of product, the nitrogen purge is not practical. As a variant that can Abe run in a chem lab, pilot plant or even a manufacturing plant would be to take your reaction product concentrate and get it into a high boiling inert solvent. Toluene is probably not high enough. I would try using xylene. I would set it up to distill at atmospheric pressure and distill and replace the distillate with fresh xylene. You can then distill the xylene (you should be able to do it in a plant with pressurized steam heating). Maybe, your pyridine acid would crystallize out of the xylene when you are done. I have done this in a plant using xylene or mestylene or even Dowtherm A (the commercial eutectic mixture of diphenyl and diphenyl ether).
Remove aceric acid by forming azeotrope with heptane i.e. add small portions of heptane and remove it in the rotary, repeat it several times till you do not smell acetic acid any longer.
Heptane may lead to phase separation; if so, toluene might perform better. You can distill out the toluene-acetic acid azeotrope, then add water and distill out the toluene-water azeotrope. That should leave you with just water as the solvent.
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