Hello everyone, I am currently performing Schiff base synthesis to obtain imine with 3-methoxybenzaldehyde and a variety of amines (p-aminobenzoic acid and p-toluidine). Based on my TLC tests, products can be found in the reaction mixture but it is not able to be precipitated out. My current reaction conditions involve the addition of aldehyde and amine together in ethanol and left stir overnight under RT. What are other procedures that I can carry out in order to induce precipitation or purify out the imine?
Dear Mason Jarius Tangau thank you for your interesting technical question. Did you follow a literature procedure? First of all you should make sure that the reaction is complete according to the TLC. Perhaps this will require some heating of the reaction mixture. Often the Schiff base product then precipitates upon cooling. If it doesn't, you can evaporate the reaction mixture to dryness using a rotary evaporator. Then you can recrystallize the crude product from methanol.
For a typical example please have a look at the following useful article:
Synthesis of Some Salicylaldehyde-Based Schiff Bases in Aqueous Media
Article Synthesis of Some Salicylaldehyde-Based Schiff Bases in Aqueous Media
This article is freely available as public full text on ResearchGate.
Frank T. Edelmann should I attempt to heat it at the end of the reaction or throughout the reaction? Moreover, the solvent for my reaction medium is ethanol. Would that interfere with precipitation?
You can find an easy method to get Shiff bases here: 10.1021/ja0034388 . Without solvent just mixing the two reagents and heat them up in some cases.
Dear Mason Jarius Tangau I think it's a safe bet to stir the reaction mixture over night at room temperature. In case that no precipitate forms, you can then heat it to reflux for a few hours and see what happens. Good luck! At some stage it would be interesting to learn if you have been successful with your experiment.
If your product dont affect by water you can percipitate it by water. If your product affect by water you can percipitate it by removing solvent molecule unde vacuum.
Frank T. Edelmann Thank you for the insight! I was able to synthesize out several of my compounds just by mixing the starting materials together. It was pointed out to me that my crude product could be in a liquid form (the reaction mixture was concentrated via rota vap to yield a yellow oil). Now, i am attempting to purify it by dissolving it in hot ethanol and cooling it.
Mason Jarius Tangau Could you please provide an answer if your attempt of purification succeded. I am currently dealing with the same problem, in the case of isolation for N-salicylidene methionine Schiff base which turned out as an oily product. Thanks in advance
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