I have searched through Dictionary of Natural Products and found a reported compound. The structure of my compound was found to be identical with the reported one. However, there are some slight difference in signals for proton NMR which might be due to the use of different solvent. I am using deuterated chloroform while the reported compound was measured using DMSO-d6. Three NH-functional groups were observed with my compound exhibiting signals at 6.39, 8.15, and 10.14 ppm as opposed to the reported signals at 8.14, 10.55 and 10.79 ppm in 1H NMR spectrum. Thus, I would like to figure out the novelty of my compound. Is the use of different solvent for NMR analysis the cause of such difference in signals?
I would greatly appreciate any opinion or suggestions about my question from any professionals and researchers in the field. Thanks in advance
Dear Chung,
The slights differences could be explained by the kind of solvent. Have you noticed differences in other signals ? If not, it's well known that echangeable protons, bearing to OH, NH and SH- functional groups, are very sensitive to electronic interaction and pH. That why you should compare other kind of protons than echangeable ones. Furthermore, try to acertain the stereochemistry of your compound (alphaD, CD), it may be a diastereoisomer.
I hope that my advices will help you
Best regards
Mehdi BENIDDIR
Get all the NMR (1D and 2D) and mass spectrum of the compound. 1H NMR will not alone be helpful to identify the compound's novelty
Dear Mehdi Beniddir,
Thanks for your answer. I have measured all 1D and 2D NMR for this compound. The differences in other signals are relatively small. With your explanation, I am quite sure that my isolated compound could actually be the known compound reported previously.
Thank you for your clear explanation which certainly helped me to clear my doubts.
Dear Lim
Its fine. 1D and 2D NMR you have done so please study them
Regards
VS Rana
IARI, New Delhi
I am agreed with other researcher. Like if you change nmr solvents, there will be definitely some shift in peaks in HNMR. Why don't you try the same solvent then? It will be easier for you to compare the results.
Thank you for all the suggestions and comments. I am greatly appreciate for that. Now, I have made it clear that the difference in chemical shifts might be due to the different solvent used for NMR analysis.
Anyhow, I will take this opportunity to study this compound this time and use for future reference.
The chemical shift differences for the NH protons are entirely consistent with the solvent change. DMSO is a much stronger H-bonding solvent than chloroform, causing significant shifts to higher frequency for NH and OH protons. The one NH shift of 10.14 ppm in CDCl3 suggests a possible intramolecular H-bond involving that proton. You could check to see if your structure is consistent with a bond like that.
just do melting point to confirm if you have the same compound. It is an old, simple and time-tested technique.
just as a complement to the previous answers, 13C NMR chemical shifts are much less influenced by solvent changes than are 1H NMR chemical shifts
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