How can I calculate a carbon-proton coupling constant for a molecule?

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I'm trying to explain a missing HMBC peak, and having a coupling constant less than 10 Hz would do that nicely. It's a formamidine derivative with a 3 bond correlation N=CHNC The C is a quaternary carbon in a benzene ring. Any help would be appreciated.

asked Feb 04 '11 at 08:23

Toth
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You may be able to compute the required coupling constant using Gaussian.

I do not have any experience with the type of molecules that you have mentioned. However, it is probably worth repeating your experiment with a different set of experimental parameters, such as varying the delays and to use a different magnetic field strength, preferably higher, before attempting a QMech. calculation. Signals from quaternary carbons are sometimes suppressed due to inadequate relaxation delays. In addition, tuning the delays used to produce the coherence may alter the set of observable couplings.

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answered Mar 05 '11 at 07:01

sekhar Talluri
621

updated Mar 05 '11 at 09:58

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Asked: Feb 04 '11 at 08:23

Seen: 8,501 times

Last updated: Mar 05 '11 at 09:58

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