We have been trying to prepare ms-tetra (4-dimethylaminophenyl) porphyrin. In the reaction vessel we added freshly distilled pyrrole, 4-dimethylaminobenzaldehye, nitrobenze, propanoic acid and acetic acid. The crude product was purified using column chromatography. The major product was wine coloured but it uv spectrum was not that of porphyrin molecules. We did have an eluent that had the porphyrin spectrum but it yield was low.
Any help please on how to improve our yields of the product we want
Hi Reama,
I used to prepare cationic porphyrins. Your major product may be a reduced form of porphyrins. So you should bubble the reaction mixture with air compressors during and/or after reaction. Or you can oxidize it by, for instance, DDQ.
Yoshinobu Ishikawa
Thank you for your response. We nitrobenze to oxidize the reaction. Would try bubbling compressed air.
Thank you
I would suggest you to avoid using nitrobenzene and acetic acid. Instead, you can try refluxing (90 min to 2 h) in propanoic acid alone, followed by distillation of the solvent and recovering the product through column. Its a two component porphyrin synthesis and hence should not be that complex.
Alternative you can attempt the synthesis through dipyrromethanes. Reama George
Hie. First make sure your aldehyde is pure. Now dissolve your aldehyde in propionic acid and reflux. When aldehyde solution is refluxing, add your pyrrole as a dilute solution in propionic acid slowly (drop wise) and allow to reflux for 2 hours. For work-up, dilute with large amounts of water followed by slow addition of saturated solution of sodium bicarbonate until product precipitates. You can then filter off the product and further purify with column chromatography.
Thank you. It seems simple enough. No need adding an oxidizing agent then?
No need. Further purification can then be done by chromatography.
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