NMR Spectra of Common Deuterated Solvents

Residual Peaks Observed in the H NMR Spectra of Common Deuterated Organic Solvents... 

RESIDUAL PEAKS OBSERVED IN THE 1H NMR SPECTRA OF COMMON DEUTERATED ORGANIC SOLVENTS... 

The following table lists the residual peaks that are observed in the H NMR spectra of common deuterated organic solvents. These peaks are generally attributed to the nondeuterated parent compound that serves as an impurity and are marked with an asterisk. In addition, other less significant peaks often arise due to other impurities. 

It is very difficult to achieve H NMR spectra of anthocyanins without an intense water peak around 5 ppm, which may overlap with signals commonly representing anomeric protons. After some hours of storage in the acidified deuterated solvent, this peak tends to migrate upfield -0.4 ppm. It is therefore advised to record H NMR spectra immediately after preparation to reveal peaks which may be hidden under the water peak, and to repeat this procedure after several hours as well. 

As CDCI3 is one of the most popular deuterated solvents used in the organic laboratory, the chemical shifts in ll NMR spectra of the most common laboratory solvents as trace impurities are in Table 1.11. 

Most NMR experiments with resveratrol oligomers are performed in deuterated acetone. This solvent has proven itself ideal for this class of compounds due to the high degree of solubility of the resveratrol oligomers and the lack of overlap between the solvent and analyte peaks. The second most commonly employed solvent is deuterated methanol, with deuterated dimethyl sulfoxide and pyridine used only occasionally. In some cases the NMR spectra of some O-methyl and O-acetyl resveratrol oligomer derivatives have been collected in deuterated chloroform [51,57,93,103]. 

Solvent. For all practical purposes, NMR spectra are recorded in solution, although pure ( neat ) liquids and even gases can, in principle, also be examined. The solvents must meet certain requirements (Sec. 12.1) and a compromise must often be employed between using concentrated solutions (for high sensitivity) and dilute solutions (for measuring chemical shifts uninfluenced by solute-solute interactions). Besides the commonly used carbon tetrachloride, deuterochloroform, and D2O, a range of deuterated solvents (dimethyl sulfoxide, benzene, pyridine, acetone, dioxane) is commercially available. It must be emphasized that direct comparison of chemical shifts obtained in different solvents is invalid, as solvent-induced changes of up to... 

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