Usually aldehyde peak in NMR appeared around 9.3-9.7 in our study we isolate many compounds with aldehyde peak around 11 so i would like to know why ?
Usually aldehyde is between 9.5 and 10.5 ppm.The chemical shifts of these proton vary in different solvents, and with temperature and concentration.
Maybe you have some hydrogen bonding or tautomerie.
If your compound is an aromatic one with some substitution at orthoposition with respect to aldehyde group. Then there is a chance of hydrogen bond. Then chemical shifts may change from normal values.
Aldehydes are easily oxidized to carboxylic acids, even by atmospheric oxygen. Be sure your product is really an aldehyde and not the corresponding acid. Carboxylic acid protons are more variable than many other types, but could easily come at 11 ppm.
Aldehyde siganals usually appear at 9-10 ppm when isolated. Conjugation usually shields a bit the aldehyde signal upfield. I have seen aldehyde signals at about 8.5 for certain substituted benzaldehydes.
Give us more information on the structure, if you want more on the subject.
1992 I have published a paper with prof, David Brown UCD regarding NMR technique n5C5H5Fe(CO)2CHO at temp. -80 degree the beak was 14.15 ppm which at -50 degree the peak has shifted down field and we got the hydride n5C5H5Fe(CO)H at 11.25 ppm
I think you should do IR and C13 to be sure it's aldehyde, as Mark mention oxidation of aldehyde is easy and the Carboxylic acid peak appear at around 11.
also I recommended a D2O H1 NMR to make sure it's not an acidic proton that you have.
Best
2D NMR experements namely HETCOR
sutible in this case where the correlation between C an proton of aldehyde group
Thanks for all who replied, in fact we checked everything H-NMR, C-NMR , HSQC, HMBC, Mass and we confirmed its and aldehyde group so the theory of Preethanuj Preethalayam @ its the most reasonable i think. Please anyone else have informations similare share it with us .
Aldehyde proton RC(=O)-H, 9-10. Carboxylic Acid RCO2H, 9.5 and above (broad). 10+
Aldehyde hydrogens are highly deshielded and appear far downfield as 9-10 ppm.
HSQC is filtered to include a certain coupling constant JC-H which is selected by the user running the experiment. Perhaps that of aldehydes was left outside just because of this.
Probably there may be anisotropic environment in your compounds. That is effecting the chemical shift in NMR spectra.
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