Two isomers of the aldehydes have the same polarity and could not be purified by column chromatography (by using any cosolvent system); re-crystallization was also not possible, as it is viscous-oil and soluble in all solvents (hexane to methanol). There are 3 possible attempts, 1. reduce them to alcohol or 2. convert them to vinyl (by PPh3CH2Br) 3. Alternatively convert them to Schiff base followed by hydrolysis........which one of the method can give the separable product?
But, how to separate bisulfate adducts of these two isomers? Is it possible by any method?
is there any difference in the structure? (one have nitrogen or phenolic OH while the other have not )
This will enable you to make use of amonia or acetic acid in the sepration.
Both have same structure only in the difference of the position of -CHO; basically it have two N-alkyl groups.
I suggest also dinitro phenyl hidrazone derivatization, to separate them
Because recyrstallization was not possible as it is a liquid, I would oxidize them to acids and then use this purification technique to separate the isomers..
You can try NaBH4 reduction method. You can use 0.25 NaBH4 and perform the reaction at low temperature. Two isomer having different chemical reactivity so one isomer reduced fast .
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