Hello all, I have one question; why I should do MPLC for my reaction and on TLC it showed only one major product?
synthesis of iminosugar
Based on what i read, about the only reason to do MPLC is if there are any minor impurities that you want to remove. When I run a TLC on a reaction, I run the reaction mixture and also the starting materials so I can confirm the reaction is complete, and I could resolve the starting materials from the product if needed. Since you can see your product on the TLC plate, compounds from potential side reactions would also be visible (ie spots under UV light, or visible with the spray reagent you are using). I didn't read how the spots are being visualized, but a sulfuric acid char is fairly universal (silica or alumina TLC plates), so you can see almost every spot.
About the only other thing I might do is try a TLC in a different solvent system that causes the spot to move, just in case a side product elutes the same time as your compound with the TLC solvents you used already. For example, if the compound ran with hexane/ethyl acetate, I would try hexane/dichloromethane (DCM) since the DCM may cause the peaks to elute differently than the ethyl acetate.
If you have access to LC-MS, run it there to verify the correct compound was made. I once synthesized a compound which oxidized; but I found our with the mass spectrometer.
What was the indicator you used on the TLC plate? Some materials like inorganic salts may be in your product and not show up on the TLC plate. This all depends on the process used for visualizing the compounds on the TLC plate. MPLC will remove many of these impurities especially those that run in the solvent front (like waxes and hydrocarbons) and those that remain at the origin like insoluble salts. Sulfuric acid charring may not show some hydrocarbons and inorganic salts which may (or may not) show up with an alternative stain like iodine. The MPLC can also remove water from your product which does not show up on TLC. Having run many microanalyses and coming up with either deficit CHN values due to inorganic salts (like sodium sulfate used for drying), or high hydrogen values from water; it is definitely worth the time and effort to run an MPLC or short column purification.
- Badges
- Science method