Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: Maxim_ on May 23, 2020, 03:53:19 PM
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Hi,
For our exam we need to be able to identify a molecular structure given certain spectra. Doing this when only a single Hnmr spectra is given is usually doable as the structures are not overly complex, but I find that generally the more information the professor gives, the more complicated the structure is.
I have attached the spectra for this particular problem as .png files.
Some of the questions I have that prevent me from puzzling this together are:
- Is the signal in the HNMR at 1.5 ppm a doublet of multiplets? when looking at the hnmr i would say no but the cosy spectrum shows it as a single signal?
- There are significantly more C signals (11) compared to H signals (4/5) and i struggle to find a way to connect these together. Am I supposed to just add a bunch of Cl or something instead of H on carbons?
- When looking at the C Spectrum the 5 signals at 70-90 ppm make me suspect i have a ringstructute substiture (cyclopentane/cyclobutane?) but i dont have a reason why the shift is so far downfield.
thank you very much for taking your time to respond,
kind regards,
Maxim
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Any carbon bonded to four other carbons or any carbonyl (C=O) carbon (with the exception of an aldehyde) will not have a directly attached proton. Is the NMR solvent CDCl3? If so, you will see evidence of the solvent in both the H-1 and C-13 spectrum, and you may recall that deuterium is a spin-1 nucleus. Not all compounds will follow first-order rules of coupling, and you may have a compound that does not.
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The three closely spaced lines in the vicinity 77-78 ppm in the C-13 spectrum are from the solvent and may be ignored.