Hi researchers,
I am currently synthesizing sulfonamide compounds by reacting aminoacetophenone with cinnamaldehyde using 6M NaOH (catalyst) and aqueous ethanol (solvent) at room temperature under the Claisen Schmidt Condensation reaction. After the reaction was completed, I found some impurities in my sample, therefore I ran column chromatography at a solvent ratio of 8:2. (Hexane: Ethyl acetate). After the column, still, my product was impure. still, there were one or two impurities. so, I'm doing recrystallization after column chromatography.
But, the problem is some of my sulfonamide compounds were found to be oily after column chromatography.
Questions:-
1. Can I proceed crystallisation technique with an oily sample after column chromatography? any suggestion or advice on how to purify my compounds after column chromatography?
2. how to recrystallise an oily sample?
3. my sample was also found to be very lesser after column chromatography. Any suggestion on how I can recover the maximum sample amount during column chromatography, please? ex before column (crude amount): 2 g after column (purified sample amount): 20 mg
thanks
An oil or oily substance is no problem. Heat a suitable solvent to boiling and use minimum solvent to dissolve your sample. Cool it down slowly, if you see it oiling out, try use abit excess on solvent or simply decant the solution to another dish.
Your elution solvent is incorrect. Your sample will elute best at a solvent system that gives it a 0.5 Rf value. Try different ratios with TLC until you get roughly 0.5 Rf, run column with this ratio and +-10% of hexane
Dear Priya,
first of all: is the synthetized substance solid at room temperature? Or is its "nature" oily? Did you use silica for chromatography? Silica often hydrolize amides, and this may be the reason of the product lost
Dear Priya,
If you still did not get the solid by Richard Pavlov's method, just warm the oil around 40C if its stable enough then added equal volume of PE:MeOH, stirr you will probably get some of your product precipitation.
Dear Priya,
Acid or alkali compounds can be added to make the product salt, and then recrystallize. If you want to improve the yield, you can use lower mesh silica gel column and then recrystallize.
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