I predicted the chemical formulation in chemdraw and predicted the HNMR. Actually, I predicted the chemcial formulation from FTIR.
But the obtained HNMR is very different from my prediction. And insead of the DMSO peal at 2.5 ppm it is showing at 40 ppm. I seek some guidance urgently.
Thanks in advance,
Nasim
Experimental NMR spectra are referenced to TMS being (arbitrarily) 0 ppm.
You need to subtract the chemical shift of TMS as would be calculated using chemdraw.
Dear Nasimul,
The 13C-chemical shift for DMSO is actually very close to 40 ppm. Please double check that you did not accidentally simulate the carbon spectrum. If you did, it makes sense that the spectra are very different.
yes sir, it was 13C. Sorry sir.
Dear sir,
Can you tell me how to guess the chemical bonds in NMR. Depending on FTIR I predicted something, but it seems to different in NMR.
I am doing trial and error, using chemdraw prediction, to find the actual molecular structure. If there are some basic knowledge in the NMR specturm, I could increase my precision.
Dear Nasimul,
I am not sure what you are trying to do here. Do you have an actual NMR spectrum of your compound and are you trying to match it with prediction? If you want to solve the molecular structure of your compound, I would suggest to run the following experiments: 1H, 13C (APT), COSY, HSQC, HMBC. There are plenty more experiments possible, but this basic set of experiments would be sufficient to solve most small-molecule structures. As for how to perform the interpretation of those spectra you would need some basic knowledge of NMR spectroscopy, which any synthetic chemist out there could help you with.
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