Hello,
I am doing an alumina column (neutral, activity I) with ether and methanol as eluents. When doing the deposit, I dissolve my sample in DCM adding a few drops of DMF. After all, I obtain my product but I always see additional peaks in NMR which I can't attribute (side reaction?)
Can this be caused by the use of DMF? Because it is not the first time that it happens
Buncel (Chem. Comm, 1970) investigated the hydrolysis of DMF by water in presence of hydroxide ions. As nanoscale Gamma alumina (the powder used for chromatography) is an amphoteric substance, presumably not entirely dry and a wonderful catalyst I would not rule out that your DMF is hydrolyzed under formation of dimethylamine and formiate.
Cf.: D.R. Burfield, R.H. Smithers, "Desiccant efficiency in solvent drying. 3. Dipolar aprotic solvents", J. Org. Chem., 43(20) 1978, 3966–3968.
Frank Kern, Carlos Araújo Queiroz thank you very much for your answers, I will look into them
Hello,
I agree with the answer of Frank Kern concerning the catalyst effect of alumina. Can you exclude that your product will not react under these conditions with one or the other components (dimethyl amine or formiate) in this system?
Wolfgang Knoll yes it probably does react. Because when I don't use DMF, I get a cleaner product (still using some drops to solubilize my product) and I think I see the peaks corresponding to formiate in NMR which supports Frank Kern's supposition.
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