I have a question about compounds that oil out of solvents after drying.
How would I analyze this? Could I make a KBr pellet, or would I just be able to analyze it in UV spec?
I assume that the solvents used to dissolve the compound, would be used as a blank, right?
I tried to dry off the solvent used to dissolve the compound and it wouldn't completely dry off, and this is why I think it was oiling out of solution. I was originally planning on trying extraction after drying off the compound. I had no choice but to try to go and re-dissolve the compound in a solvent (CH2Cl2). It looked like it dissolved, but I'm not sure since the pasteur pipette looked as if it had an oily residue after I pipetted the solution over to another container....
Not sure what to do now,
Thank you
I have no idea what "oiling out of solution" means. Sure you can make a KBr pellet. AND you can run the sample on a UV. Can it be that part of the unknown dissolved in CH2Cl2 and the "oil part" was another compound? If I thought some had dissolved in CH2Cl2, I would attempt to recover the part that dissolved. That could be a pure component.
I dried a solution of solvent + unknown compound dissolved in it, and it would not fully evaporate off and leave a residue. What was left over no matter how much I heated the watchglass was stagnant droplets as if I was using dirty glass and I had poured a solution over it. (i.e. diry volumetric flask after pouring solution out, has stagnant droplets of water)
I'm not sure if the oily substance was another compound. Hopefully it is not. I ran a plate and it showed 1 strong spot and 1 weak weak spot and my prof. said that it looks like it is one compound. This is the reason I tried to evaporate off the solvent and see if I could just see one compound or 2 after using this to spot another plate, therefore elminating the chance that it is solvent interaction that is causing the second spot.
I will try to analyze the CH2Cl2 with the unknown in it and see what happens.
Thank you Dr.Bob
Analyzing compounds that oil out of solvents after drying can be a challenging task. Here are some steps you can follow to analyze such compounds:
1. KBr Pellet: You can try making a KBr pellet for Fourier Transform Infrared (FTIR) spectroscopy. This technique allows you to analyze the functional groups present in the compound. To do this, mix a small amount of your dried compound with dry KBr powder and press it into a pellet. Then, perform an FTIR analysis of the pellet to obtain the infrared spectrum of your compound.
2. UV Spectroscopy: UV spectroscopy can provide information about the absorption properties of a compound in the UV wavelength range. However, it might not be the most reliable technique for analyzing compounds that oil out of solvents after drying. UV spectroscopy is more commonly used for compounds that exhibit strong chromophores or have conjugated systems.
3. Blank Analysis: Using the solvent you used to dissolve the compound as a blank is generally a good practice. It helps to account for any absorbance or interference from the solvent itself. If you are using a spectrophotometer, measure the absorbance of the solvent alone and subtract it from the absorbance of the compound solution.
4. Drying of Solvent: If your solvent is not completely drying off, it suggests that the compound might not be fully soluble in the solvent or that it has a high boiling point. In such cases, it is possible that the compound is oiling out of solution. One approach would be to try evaporating the solvent using a rotary evaporator or a gentle stream of nitrogen to see if the compound remains behind.
5. Re-dissolution and Observation: If the drying process does not work, you can try re-dissolving the compound in a different solvent, like CH2Cl2, as you mentioned. After pipetting the solution into another container, observe if there is any oily residue left on the pipette tip or inside the container. This observation can give you an indication of whether the compound has dissolved completely or if it is oiling out again.
If you are unsure about the next steps or if the analysis becomes complicated, it would be helpful to consult with a lab supervisor or an experienced chemist who can provide further guidance and expertise.