Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Urbanium on April 22, 2015, 09:44:40 AM
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Is anyone aware of a TLC dip which does not oxidise the "oxidisable" spots on the plate (KMnO4, Goofy etc.), but instead acts as a reducing agent?
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Goofy
I had to google that. Where does the name come from? I've always known it as CAM...
I found a recipe for 0.1% morin (http://en.wikipedia.org/wiki/Morin_%28flavonol%29) in MeOH (source (http://www.chemistry.mcmaster.ca/adronov/resources/Stains_for_Developing_TLC_Plates.pdf)). Presumably morin is an antioxidant, so the mechanism would be reductive... I've never used it.
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What compound or class of compounds are you trying to visualize?
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The compound has two alkyls and few of sulfurs and oxygens between, like an alternating ether-thioether system. For some reason I can't oxidise it, but since the whole compound is a dimer with an S-S bond in the middle, I was thinking of reductive cleavage on the TLC plate.
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Once reduced, you can use a TLC spray based on Ellman's reagent. Thioethers? IIRC we once tried a method that we found referenced in a paper coauthored by Isaac Asimov. I think it used azide, but I don't believe that we had great success with it.
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The compound has two alkyls and few of sulfurs and oxygens between, like an alternating ether-thioether system. For some reason I can't oxidise it, but since the whole compound is a dimer with an S-S bond in the middle, I was thinking of reductive cleavage on the TLC plate.
Maybe hydrogen peroxide? we learned that thioethers can be easily oxidized to sulfoxides or sulfones
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G. E. Howard and J. Baldry, Analyst 94 July 1969, pp. 589-593
These authors use chloramine T for thioethers and perhaps disulfides. I don't recall having tried this myself. The azide method I mentioned used iodine, and it came from Chargaff's lab in 1948. We did not have much luck with it, but we did not try very hard.
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Acta Chemica Scandinavica 1960 14:1980-1984. Stig Akerfeldt used 1% CuCl2 in 50% ethanol containing 5% ammonia as a spray reagent to produce black spots for cysteamine S-phosphate on paper. It also reacts with thiophosphate, but I am not sure how other compounds would behave.
Erratum
In regards to my previous message, I had a look at the 1969 paper by Howard and Baldry. They did not use chloramine T for TLC detection; it was a reagent.
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A test thioether stained nicely with basic permanganate.