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Topic: Problem in compound identification  (Read 8655 times)

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Offline goldy

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Re: Problem in compound identification
« Reply #15 on: September 07, 2010, 01:49:34 AM »
Quote
Racemised during isolation

To explain discodermolide's answer a little more fully, it's not the plant that's making a racemic mixture, the racemisation occurs afterwards in the methanol mixture at elevated temperatures. This means that you could be having the same problem yourself, especially as you're running your HPLC in MeOH.

And in reply to your earlier question, you will have to analyse all four peaks separately. I also recommend a mass spectrum for each compound.
I am running HPLC in ambient temperature. These compounds are overlapping with each other. I also injected them in mass and all four peaks have same mass (lil difference in dicimal value). I want to separate these compounds but doesn't seem possible.

Offline lavoisier

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Re: Problem in compound identification
« Reply #16 on: September 07, 2010, 01:38:08 PM »
Unless you're using chiral HPLC, you won't see two enantiomers as two separate peaks.
So 4 peaks, on a non-chiral HPLC column, which have all the same mass (this should be checked by MS-search), are 4 isomers.
This doesn't imply they are stereoisomers (they could be constitutional isomers), and doesn't answer your initial question.

The NMR of your original isolated spot is what you need first of all.

You could also run the LCMS in basic conditions.

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