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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: foxp on September 21, 2006, 03:28:45 PM

Title: Will keto-enol tautomers present different spots onTLC?
Post by: foxp on September 21, 2006, 03:28:45 PM

If the ratio of ketone to enol is great enough, and the polarity between a ketone and enol is different enough, how does it behave on silica TLC? Smear? Two spots?  No separation ever?

Title: Re: Will keto-enol tautomers present different spots onTLC?
Post by: Borek on September 21, 2006, 04:03:24 PM

Equilibrium is a dynamic thing...

Title: Re: Will keto-enol tautomers present different spots onTLC?
Post by: foxp on September 22, 2006, 08:10:57 AM

So I should see one spot and the rf is the result of the average polarity between the two tautomers.

But correct my thinking if I'm wrong, but the silica plates adsorb due to hydrogen bonding, and if the equalibrium dictates that 11% of the compound is in enol form at the instant it is spotted on the plate, then that 11% has a different interaction with the silica than the 89% that is in ketone form.

I guess the equilibrium might be pulled in the "enol" direction and the average polarity still results in a single spot.

Title: Re: Will keto-enol tautomers present different spots onTLC?
Post by: Borek on September 22, 2006, 11:20:41 AM

Quote from: foxp on September 22, 2006, 08:10:57 AM

the average polarity still results in a single spot.

That's what I will expect.