Hi Seok,
Check through the article attached if you can find your chemical shifts.
The chemical shift is alright. but the doublet instead of septet could be due to shimming problems, check other solvents to confirm there is no shimming issue.
if you resolve the issue, share with us too
Chemical shift is ok, but septet is expected. It might be due to the shimming problems as previously mentioned by Adil S. Aslam. This type of shimming problems mainly occur in solid state 13C NMR of some polymeric samples. Thank you
Dear all, thanks a lot for all the comments. Attached as the 11 signals that i got from the sample. Could it be consider as 11 carbons?
The spectrum is a typical carbon spectrum of a long chain fatty acid. With the resolution you show it is not clear how many carbons are in this region where the CH2 groups appear. You should see about 5 more signals at ca 15, 23, 25, 32 and 34 ppm. These correspond to the carbons at the methyl end (15 - -25) and the carboxyl end (32 and 34) respectively. Then the carboxyl will show at ca 175 ppm. Unless you see signals in the 110 - 120 ppm region you are dealing with a saturated fatty acid.
Based on the attached results, could it be a diester compound as it has 2 signals at 176 ppm and 4 signals at 62 - 69 ppm? There are 18 signals at 13 - 29 ppm, 5 signals at 31 - 39 ppm, 7 signals at 124 - 129 ppm. Total signals are 36. Can we confirm the structure by this C-NMR or it is compulsory to conduct H-NMR?
Dear Seok Fang,
I do not think your interpretation is correct. In each of the regions you have multiple peaks of greatly differing intensities. If we just look at the peaks with the largest intensities then we find a C=O some potential C=C and the expected signals between 30 and 10 ppm for a long chain fatty acid. Then we have a larger number if signals with lower intensity. Those appear in all regions expected for saturated or unsaturated fatty acids. But the signals for glycerol between 70 and 60 ppm appear only with lower intensity. This indicates that a gylycerol ester is only a minor component in this sample. The glycerol region seems to show more than 3 signals so again indicating that you are not looking a a single product. My guess is the sample consists mostly of a fatty acid with some other compounds.By the way the signals around 29 ppm are not R3CH but R2CH2 with the ones closest together in a ...CH2-CH2-CH2.. chain. .
Thank you for the answer. I would like to confirm the structure using MestReNova software. However, I can't find carbon nmr analysis in that software. Do you have any ideas to confirm the structure of this compound?
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