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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

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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.

link

answered Mar 05 '11 at 07:01

sekhar%20Talluri's gravatar image

sekhar Talluri
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updated Mar 05 '11 at 09:58

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