This question may have been raised before in AMMRL but I don't remember a definitive answer. Since I'm writing a book, I need to know if there is any source of standard chemical shift values for the 13C solvent peak. There seems to be a lot of disagreement (and some outright errors) in the charts put out by the isotope companies. Here is what I'm writing in the book:
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The chemical shifts of these deuterated solvent peaks (relative to TMS at 0 ppm) are dependent on sample concentration, and there is no agreement on exact values to be used to reference the 13C spectrum. For this reason, the reference chemical shift used should be specified in the experimental section of any publication; e.g. “13C chemical shifts in methanol-d4 are referenced to the solvent peak at 49.15 ppm”. In deuterated water (D2O) there is no solvent carbon peak, so a standard like methanol (CH3OH, 51.72 ppm) or dioxane ([-CH2-CH2O-]2, 66.5 ppm) must be added.
chloroform-d CDCl3 77.0 ppm 3 lines (1:1:1)
dichloromethane-d2 CD2Cl2 54.0 ppm 5 lines (1:2:3:2:1)
acetone-d6 CD3COCD3 29.9 ppm* 7 lines (1:3:6:7:6:3:1)
DMSO-d6 CD3SOCD3 39.5 ppm 7 lines (1:3:6:7:6:3:1)
methanol-d4 CD3OD 49.15 ppm 7 lines (1:3:6:7:6:3:1)
benzene-d6 C6D6 128.4 ppm 3 lines (1:1:1)
pyridine-d5 C5D5N 150.4, 136.0, 124.0 3 lines each (1:1:1)
*There is also an acetone-d6 carbonyl peak at 207.0 ppm (singlet)
Please comment if you have any better information. The CH3OH in D2O value seems high to me, but I measured it against TSP-d4 twice.
Neil
Neil E. Jacobsen, Ph.D.
NMR Facility Manager
Department of Chemistry and Biochemistry
University of Arizona
1306 E University Blvd.
Tucson, AZ 85721
520-621-8146
Received on Tue Oct 07 2014 - 06:42:56 MST