Hi friends,
I have carbon -13 NMR for potassium phenylethynyltrifluoroborate (PhCCBF3K) ,using 600MHZ,the carbon-carbon triple bonded were not showing in the spectrum can any one know, or help, why it's signal disappear in the spectrum? Thanks.
Hi all ,
prof. Gordon, the signal is not buried under noise ,I did from 250 to 1000 repetition.
prof. Michael, Thank you for your suggestion. The instrument is NMR 600MHz, The spectrum was collected at 100MHZ.
Mis . Xu , The instrument is NMR 600MHz. The spectrum was collected at 100MHZ.
Thank you all for your reply .
I agree with Michael Päch and Gorden W. Driver. The carbons bounded to boron (NMR active nucleus) in alpha and beta position, both have a high coupling to the boron (1J and 2J) therefore you get a multiplett because 11B (81% abundance) has a spin of 3/2 and 10B (19% abundance). Also the fluor-atoms (2J) make a quartet-multiplet with the alpha 13C-carbon with about 20Hz. In a normal 13C-spectra with power-decoupling you don't get a NOE-enhancement from the protons and therefore the signal is weak. To see the multiplett you need much more scans.
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