The reaction mixture is poured onto water, but it is still remained sulfur salts. Positive sulfur test for benzimidazole containing no incorporated sulfur. And SO2 and SO3 fragments appeared in the mass spectrum.
Benzimidazole is basic compound - so it may be sulfite or sulfate salt. Add suitable base (water ammonia, Na2CO3) during work-up.
If possible, a filter column chromatography is recommended. Else, crude product needs to be dried to remove the trace amount of water used in the reaction. Then dissolve the crude product into dry methanol and filter it to remove the undissolved inorganic salt. You can add a small volume of chloroform into the clear filtrate to remove the trace amount of dissolved salt by filtration.
But the Benzimidazole derivative is partially soluble in hot methanol. And i will lose large quantity of the benzimidazole.
Use Dry Flash Column methods to clear out the inorganic salts and remove the solvent in the usual way followed by recryx. A buchner funnel attached to the water pump holds silica gel and the sample is dissolved and slurried with clay. See: Dry Column Vacuum Chromatography
Dry Column Vacuum Chromatography
Daniel Sejer Pedersen,* Christoph Rosenbohm
Cureon A/S, Fruebjergvej 3, 2100 Copenhagen, Denmark
Fax +4570260097; E-mail: [email protected]
Received 5 August 2001; revised 10 September 2001
After pouring the reaction mixture onto water, extract with AcOEt (several times). Then dry the organic layer over magnesium sulfate and removed under vacuum. Purify your compounds by chromatography on silica gel eluting with chloroform and recrystallization from adequate solvent.
Please, see
--- Gabriel Navarrete-Va´zquez, Hermenegilda Moreno-Diaz, Francisco Aguirre-Crespo, Ismael Leo´n-Rivera, Rafael Villalobos-Molina, Omar Mun˜oz-Mun˜ iz and Samuel Estrada-Soto, Bioorganic & Medicinal Chemistry Letters 16 (2006) 4169–4173.
Good luck
Dear Khattab , is the product water soluble? If not, why don't you wash the crude product with water itself!
It is not water soluble. Actually, i will wash it with water and adjust the pH above 7. Maybe between 7-9. As the benzimidazole is basic in nature.
Add into suspension of product small amount of H2O2 (oxidation of S(IV) to sulfate), excess can be detect by iodide - starch test paper and add excess of Ba(OH)2 in water. After stirring add dry CO2. Evaporate water and solid recrystallize from suitable organic solvent. Inorganic residuum is mixture of very bad soluble Ba2+ carbonate and sulfate.
Easily, you can pour it on water then wash the ptroduct with ether and separate the organic layer by separating funnel then the organic layer is
evaporated in vaccu leaving the desired product.
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