Tuesday, November 15, 2011
Reverse Phase Silica - Sort of!
I'm sure that all the synthetic organic chemists will agree that column chromatography is something we simply couldn't live without. At our Department we use it in all its forms: Automated flash chromatography, Chromatotron, Prep. HPLC (Chiral and RP), Prep. TLC, old skool manual flash and DCVC columns etc. However, in spite of all this we all too frequently end up with stuff that is a major pain to separate. Just last week a colleague of mine, lets call him Bernard, told me he had used deactivated silica for purifying his compound - the only thing that had worked for him! So now you are probably thinking deactivated silica??? Normal lab terminology translates this to treating your silica with some amine base prior to use but this is not what Bernard was talking about. He found this paper (Procedure in the Supp. Info.) where they derivatise silica gel with ethyltrichlorosilane. Cheap reagents and a simple method. I guess the "deactivated" silica ends up being something between regular and reverse phase silica. Bernard simply packed a column with this stuff and put on our automated columning system to get a great result eluting with normal phase solvent mixtures. Excellent news for me and my people. We often end up with very polar compounds that will not come off a regular column or elute in fractions 1-5 on a reverse phase column.
Does anyone have any experience with this type of silica or something similar? Please let us all know by posting a comment. D!