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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: ae86 on February 02, 2021, 04:00:34 PM

Title: Assigning carbon-13 NMR for ethyl 2-oxo-3,4-dihydrochromene-3-carboxylate.
Post by: ae86 on February 02, 2021, 04:00:34 PM
Hi,

I have a molecule and an NMR spectrum, and I need to assign the NMR peaks to each of the carbons to the molecule.

I know that the 14.19 ppm and the 61.94 ppm correspond respectively to the carbon 12 and 11. However, I struggle for the other peaks especially between 116.76 and 148.51 ppm. I just know that it corresponds to the aromatic ring. Finally, I think that the 156.65 ppm and 155.15 ppm are respectively the carbon 9 and 10.

Thank you for your help.
Title: Re: Assigning carbon-13 NMR for ethyl 2-oxo-3,4-dihydrochromene-3-carboxylate.
Post by: Babcock_Hall on February 02, 2021, 07:53:34 PM
I would use calculations of chemical shifts as well as the number of attached hydrogen atoms.
Title: Re: Assigning carbon-13 NMR for ethyl 2-oxo-3,4-dihydrochromene-3-carboxylate.
Post by: kriggy on February 17, 2021, 06:08:49 AM
Exactly assigning all those signals is going to be impossible withtout further data comming from 2D experiments.