I used dichloromethane:methanol:triethylamine=10:1:0.15 as eluent, but I stored it during 3 days, so it may be a little bit concentrated.
Question 1. I used toluene to dissolve sample. If I spot only toluene and run TLC, and stain the plate, then there emerges brown color near the solvent front. I waited enough time to let toluene evaporate before staining, but are there chances that spot 1 is of toluene?
Question 2. I am assuming that my desired product is basic, so I used triethylamine. When I fixed ratio of dichloromethane and methanol and changed only ratio of triethylamine, only the position of spot 7 changed and the others are unchanged. Then can I conclude that spot 7 is not part of spot 6 or tailing 2?
(sample is more concentrated than first image)
Question 3. There are some tailings. Does existence of tailing always mean the band widening when I run the column chromatography? I heard that when I do the column, I had better use as minimum solvent as possible. But to prevent tailing, should I dilute the sample more? (I think the size of spot was small enough)
Question 4. In UV, spot 6 looks like one big spot, but after staining it seems that middle is empty. Does this mean there are two or more other compounds in same position?
Question 5. Is spot 4 and tailing 1 is same compound? Is spot 6 and tailing 2 is same compound? If I can't determine in this result, what should I do?
Another TLC image. Spot 4 is more identifiable. (sample is more concentrated than first image)
- Question 6. I assume that the longer distance spot moves, the more nonpolar it is. Even in very polar solvent system (i.e. dichloromethane:methanol=10:1) many spots are close to solvent front. To separate spot 1, 2, 3, and 4, how can I change the solvent system?
- starting material : aza-crown ether, bromothiophene, Pd catalyst, P ligand.
- expected product : N-substituted thiophene.
- aza-crown ether and spot 7 is not drawn up by solvent without (aza-crown ether is detectable only by ninhydrin) So I think I should use Et3N to separate these two.
- spot 3 is assumed to be Pd catalyst. bromothiophene and P ligand is not detectable by formaldehyde/H2SO4 staining.