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Topic: C13 NMR - Spectroscopy  (Read 2007 times)

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Offline afila2012

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C13 NMR - Spectroscopy
« on: October 07, 2012, 06:38:40 AM »
I am trying to interpret the H1 NMR and C13 NMR spectra to work out the structure of an unknown molecule but I'm having a few problems.

 I have a peak on the C13 NMR at -0.003ppm. This then shows up a tiny bit on the DEPT spectrum. At first I thought maybe just ignore it but on further investigation I'm thinking it must be a carbon in the molecule as we have a large 3 hydrogen peak in the H1 NMR which suggests it would be a methyl group.

Just wondering if anyone knows if it's possible (and can then explain why) for the C on a CH3 group to have a peak at -0.003ppm or if it's some impurities to just be ignored.

Thanks

Offline discodermolide

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Re: C13 NMR - Spectroscopy
« Reply #1 on: October 07, 2012, 08:07:40 AM »
-0.003ppm is not very far away from 0ppm.
Surely this is within the thickness of the ink of the recorder?
Is it a -SiMe group? Remembering that SiMe4 is set at 0ppm.
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