I spotted a commercial TLC plate, coated with silica gel, with a pure benzoin solution. After running the TLC plate in methylene chloride, the benzoin separated into two different spots. Rf values are 0.6 and 0.9. What explains this? A pure material should have only one spot that travels, should it not?

Question

I spotted a commercial TLC plate, coated with silica gel, with a pure benzoin solution.  After running the TLC plate in methylene chloride, the benzoin separated into two different spots. Rf values are 0.6 and 0.9.  What explains this?  A pure material should have only one spot that travels, should it not?

DrBob222 · Answer

Here is a link. Pay attention to the S and R enantiomers. https://en.wikipedia.org/wiki/Benzoin