Hi everyone,
one of our user's sample is showing the weirdest lack of 13C peaks in the methyl region and I can’t think of a way to explain it. The solvent is DMSO and the compound has CH3, CH2 and aromatics. It is believed to be a tautomer. The 1H spectrum is clearly showing the presence of CH3 (2 peaks) as expected from the structure. However, when we run 13C, no methyl groups are showing. Same when we run HSQC or APT or DEPT. Since we have no problem seeing the quartenary carbons (or the aromatic and CH2), I don’t think it’s a problem of relaxation. The only peaks missing are the 2 CH3. This happened for several derivative of the same compound but only when run in DMSO. If the sample is run in CDCl3, the methyl groups are there…
Any suggestion?
Celine
Celine Schneider, PhD
Adjunct Professor in Chemistry
Research Laboratory Associate
NMR Facility / C-CART
CREAIT Network
Memorial University of Newfoundland
St. John's, Newfoundland, A1B 3X7
Tel: (709)-864-3134
email: cmschnei_at_mun.ca
http://www.mun.ca/creait/CCART/
Received on Fri Feb 15 2019 - 08:45:35 MST