UPDATE: I used TLC to monitor the progress of my reaction, and the reaction wasn't complete so there was starting material in there, and it had no trouble getting away from the DMF, it traveled the exact same distance as the pure starting material on the left lane.
What does your compound look like? Toss some way more polar solvent in. Like acetonitrile or something.
Heres my starting compound:
I would have expected that compound to be fairly lipophilic, but it isn't really. Polar mobile phases make it race up the plate. It exhibits purple fluorescence which surprises, the same colour that my products fluoresce at. I wanna try acetonitrile next, along with the 90:10 methanol phase. .
What does your compound look like? Toss some way more polar solvent in. Like acetonitrile or something.
Some things just don't purify well on silica. You could try a different stationary phase, or a different type of chromatography (e.g., size exclusion).
You can also try adding a little methanol to the eluent (few percent).
I'm gonna try this tomorrow. A friend is running a reaction (completely different compounds though) in DMF and he told me that hes had no trouble with sticking or streaking, hes been using 90:10 ethyl acetate:methanol. I ran some solubulity tests on my compound and couldn't find anything that its easily soluble in. Diethyl ether, n-hexane, acetone, water, ethanol, none of them dissolve it well, and oddly enough it seems least soluble in ether and hexane. I added some DMF soaked precipitate from my flask to a mL of diethyl ether and white flakes dropped to the bottom of the vial. It cleaned the yellow tint out of my product. Does this mean I might be able to use ether to crash the product out of solution?
What does your compound look like? Toss some way more polar solvent in. Like acetonitrile or something.
No, I'm saying that the starting material (the structure I posted above) moves fine, but my product won't move at all. Also when the reaction isn't complete and theres starting material left over, I can easily separate it with TLC because the starting material (the fluorinated phthalonitrile) has no trouble separating from the crude product either. I tried both analysing directly and diluting it in DCM. It doesn't dissolve so well in DCM.
I'd dont wannaoo much about the products since they're new compounds, since I haven't even started characterising them so which compounds and isomers will be formed is uncertain. Basically I'm doing nucleophilic aromatic substitutions onto the ring in order to replace some of the electron withdrawing groups with electron donating ones. Each reaction I've done so far as at least 2 isomers, but I've yet to see anything move, let alone separate on the TLC plate. I'm spotting directly from my reaction mixture, but I tried dissolving a drop of the rxn mixture in some DCM to dilute the DMF but had the exact same result, I also tried just drying the DMF off with the nitrogen pump but no luck. There usually isn't even any smearing like you would expect with DFM, however I tried a 50:50 ethyl acetate/toluene moebile phase and it smeared my product up the plate about a cm. Thats a start I suppose.
Thanks a lot for the tip! Whats the salt for, just for dissolving emulsions or will it help get the DMF into the water layer too? Either way, I'd be inclined to spot both layers to see how much product is still present in the water.
I've tried multiple reaction conditions, for example, in one of my reactions involved attaching alkoxy groups to the ring. I tested two routes, first one I just added lithium metal to the ethylene glycol, and used the glycol as my solvent. Then I added the phthalonitrile and let the alkoxide ions do their thing. Second time around I used potassium carbonate to the propylene glycol then added the phthalonitrile and let it react over night. Didn't have any effect on the TLCs. Surely an excess of lithium metal would deprotonate both -OH groups of the glycol. Then I did the rxn in less harsh conditions by simply adding the precursor, along with some K2CO3 to the propylene glycol and adding a few mL of DMF. Intrestingly, the addition of DMF instantly turned the solution from clear to light yellow. Could that be a solvation effect?