[rachaelsarah97]

Hello, I am doing a paper on the extraction of alkaloids and I have a few questions.
The alkaloids I am extracting are atropine and hyoscine(scopolamine). I performed a TLC and got Rf values of 0.66 for atropine and 0.88 for hyoscine. I was curious as to why hyoscine went further in a polar eluent as from its structure (extra oxygen) it seems more polar than atropine. I understand that the oxygen is in an epoxide ring and it is strained but I am not sure as how this effects the polarity of the molecule.

Also I am having a hard time finding anything on the Vitali Morin reaction with fuming nitric acid, KOH and ethanol. So if anyone could give me any guidance in how this reaction takes place that would be great. Oh and also if the reaction colour change to purple then clear is correct and if it is for hyoscyamine, hyoscine or both.

Many thanks!

Rachael

[pgk]

a). If you try to see the molecules of atropine and hyoscine (scopolamine) in space, you will observe that scopolamine has one more oxygen in the same side with the other ones, which satisfactory explains that polarity.
b). http://www.epharmacognosy.com/2012/07/tropane-alkaloids.html
But do not confuse hyoscine (scopolamine) with hyoscyamine (daturine).
Question: There is mixture of two compounds that the one is more polar than the other and the mixture is eluted with a polar solvent. Which compound will appear first in the TLC, the more polar or the less polar one?

[rachaelsarah97]

I'm not entirely sure of what your asking.
Do you mean what substance will move further up? If that's the case it would be the less polar one.
What I don't understand is if hyoscine is more polar that atropine why did it move up more? When in the polar eluent it should technically move less?
The eluent used was acetone,water and concentrated ammonia solution so could that be more polar than the silica and thats why it moved up further than atropine?

[pgk]

Ok, then the same question is posted in another way.
In polar solvents, the more polar compound appears first. This happens in reverse phase chromatography that polar eluents are used.
In non-polar solvents, the less polar compound appears first. This happens in normal phase chromatography that usually non-polar eluents are used.
Question: with polar eluents, which compound will move up further in TLC, the more polar or the less polar one?

[rolnor]

Ok, then the same question is posted in another way.
In polar solvents, the more polar compound appears first. This happens in reverse phase chromatography that polar eluents are used.
In non-polar solvents, the less polar compound appears first. This happens in normal phase chromatography that usually non-polar eluents are used.
Question: with polar eluents, which compound will move up further in TLC, the more polar or the less polar one?

But you can use polar solvents in normalphase chromatography?

[pgk]

Sorry, bad expression.
"This happens in normal phase chromatography that usually (but not always) less polar and/or non-polar eluents are used."