I have an isolated compound from my studied plant and I am asking about the interpretation of 4 single pics in NMR 1H arriving at 11-12ppm.
How can 4 protons in the same molecule arrive to more than 11 ppm on my proton spectrum of NMR?
Can you attach the entire spectrum? Many compounds isolated from plants can be large with multiple similar peaks from multiple functional groups.
4 different aldehydes? how you know, that you have pure isolated compound? do you run H-C HSQC and HMBC?
Maybe I'm not understanding the question, but it's certainly possible to have several substantially de-shielded proton environments in a single molecule. The fact that there are separate peaks indicates the absence of rapid exchange, so aldehydes seem somewhat more likely than acids if you're using a solvent with exchangeable protons/deuterons (i.e. water). But if it's a big molecule dissolved in an aprotic solvent, one could also imagine having four isolated acid groups -- this is particularly likely if the four peaks are singlets (is this what you mean by "single pics"?). Analysis of J-couplings or heteronuclear correlation experiments (also possibly NOESY) would certainly help with assignment.
Peter Sebej, this compund is pure and purified by HPLC (Acetonitrile/ Water) and I can see the correlations too in HMBC and nothing on HSQC.
John W. Blanchard, Yes 4 singlet peaks (integration 1) at 12.60, 12.15, 12.06, 11.90 ppm on the same compound with MW=670.
If you see correlations in HMBC and not in HMQC then the protons are most likely attached to O or N.Ralf mentioned before that protons involved in hydrogen bridges are often seen at these chemical shits. Do you know the molecular formula. If there are no nitrogens all these protons would be on oxygens. You should be able to find the carbons that are attached to these oxygens from their shift and the HMBC correlations.
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