Deuterated dimethyl sulfoxide, solvent

It was shown in the same article that the decarboxylation could also be performed by conventional heating but then copper cyanide was required and a mixture of saturated and imsaturated 2-pyridones 65 and 66 was obtained in a ratio of 1 10 (Fig. 10). A tentative mechanism was suggested for the reagent-free MAOS method where the carbonyl in the 2-pyridone ring is supposed to assist in the decarboxylation yielding an yUde 67 (Fig. 11). The decarboxylated bicyclic 2-pyridone 68 is thereafter obtained after protonation by the solvent. In agreement with the mechanistic suggestion, it was shown that a selective deuteration occurred when deuterated dimethyl sulfoxide (DMSO-de) was used as solvent. 

The use of dry, deuterated dimethyl sulfoxide (DMSO-d6) or deuterated acetone has the same effect as the above treatments. In addition, the OH proton peak is moved to higher frequency by hydrogen bonding between the solute and the solvent, thus providing... 

Most deuterated solvents have residual proton impurities in an otherwise completely deuterated molecule thus, deuterated dimethyl sulfoxide, (CD,)2S=0, contains a few molecules of CD2H—(S=0)—CD3, which show a closely spaced quintet (/ 2 Hz, intensities 1 2 3 2 1) in accordance with 2nl + 1 (see Appendix G). 

Irradiation of an OH group results in nuclear Over-hauser enhancement of nearby protons. However, the usual rapid exchange rate of hydroxylic protons must be retarded either by using dry deuterated acetone or deuterated dimethyl sulfoxide as a solvent, or by simply cooling a CDC13 solution. Either process also moves the OH peak to the left this movement can be controlled to prevent overlap of absorptions, and, of course, it serves to identify the OH peak (Section 3.6.1.1). 

In contrast to the methylene hydrogens, ring hydrogens can be quite labile when substituted by deuterium atoms. Thus, in the case of ethyl (2-bromo-2-methylcyclopropane-l-(/)carboxylate (20), reaction with potassium hydride in dimethyl sulfoxide led to substantial loss of the deuterium label. However, use of deuterated dimethyl sulfoxide as the solvent led to 99% deuterium retention in the product, ethyl (2-methylenecyclopropane-l-[Pg.1441]

The structural effect is dramatically modified by the solvent the ratio kH 0 cxchangc/kraccmtzaiion is 2000 in fm-butyl alcohoW but only 10 in deuterated dimethyl sulfoxide (longer lifetime of the anion )45. If the sulfonyl group is incorporated into a planar five-membered ring the transformation yields mainly racemized product implicating the involvement of an achiral intermediate anion46. 

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]. 

The nuclear magnetic resonance (NMR) spectra were recorded on a Varian A-60 spectrometer, using deuterated dimethyl sulfoxide (DMSO) as solvent and tetramethylsilane as internal standard. IR spectra were obtained on a Perkin-Elmer 237B IR spectrophotometer. 

Figure 3.42 (a) H and (b) NMR spectra of poly(1,4-phenylene ether sulfone) in deuterated dimethyl-sulfoxide, DMSO-de. Spectrum (b) shows the NOE that occurs on proton decoupling of the 0 spectmm. The peaks for the protonated carbon atoms 2 and 3 ate enhanced by the NOE over the signals from the unprotonated carbon atoms 1 and 4. The peak in the proton spectrum at 3.3 ppm is due to water in the solvent the peak at 40 ppm in the C spectrum is due to natural C in the solvent. (From Williams, E.A. Characterization of Materials, Part I., 1992. Copyright Wiley-VCH Verlag GmbH Co. KGaA. Used with permission.)... 

Sugars are very good candidates for the measurement of VCD as the more common ECD is dependent on a chromophore, which is almost always absent in this class of natural compounds. The examination of the VCD spectra of six common sugars revealed a chirality rule for the 1150 cm band in deuterated dimethyl sulfoxide. Later the FT-VCD spectra of the carbohydrates D-fucose, D-arabinose, D-ribose, D-galactose and D-glucose [25] and their isotopomers deuterated at the hydroxyl group were examined in the same solvent. Some useful correlations between structure and spectra are found, but also some deviations. 

Ri = N3, R.2 = H), and an equilibrium is observed in the case of the deuterated compound (59 Ri = R2 = N 02). Certain secondary amino-substituted compounds (59, 60 Rj =RNH, R2 = H) show solvent dependence of their equilibria solutions in dimethyl sulfoxide contain mainly form 59, whereas alcohols as solvents favor form 60. ... 

All NMR spectra were recorded on a Varian A-60 spectrometer at room temperature by Nuclear Magnetic Resonance Specialties, Inc., New Kensington, Pa. Benzene soluble fractions were recorded in deuterated chloroform solution (CDCls) while dimethyl sulfoxide-dc (DMSO-dr.) was the solvent employed for other fractions. (Deuterated chloroform with enrichment of 99.8% was purchased from Bio-Rad Laboratories and dimethyl sulfoxide-dr, with enrichment of 99.6% from Merck, Sharp, and Dohme of Canada.) The internal standard used with the CDCla solutions was tetramethvlsilane and hexamethyl-disiloxane (chemical shift 7 c.p.s.) with DMSO-d . Prior to preparation for NMR recording, the samples were thoroughly dried in a vacuum at 110°C. The NMR tubes were sealed to minimize the absorption of atmospheric moisture. The chemical shifts given in c.p.s. are referred to tetramethylsilane. 

Fifolt [ 130] reported this chemical shift additivity method for fluorobenzenes in two deuterated solvents d6 acetone and d6 dimethyl sulfoxide (DMSO) Close correlations between experimental and calculated fluorine chemical shifts were seen for 50 compounds Data presented in Table 18 result from measurements in deuterochloroform as (he solvent [56] Fluorine chemical shifts calculated by this additivity method can be used to predict approximate values for any substituted benzene with one or more fluorines and any combination of the substituents, to differentiate structural isomers of multisubstituted fluorobenzenes [fluoromtrotoluenes (6, 7, and 8) in example 1, Table 19], and to assign chemical shifts of multiple fluorines in the same compound [2,5 difluoroamline (9) in example 2, Table 19] Calculated chemical shifts can be in error by more than 5 ppm (upfield) in some highly fluonnated systems, especially when one fluonne is ortho to two other fluorines Still, the calculated values can be informative even in these cases [2,3,4,6-tetrafluorobromobenzene (10) in example 3, Table 19]... 

For samples of low polarity, carbon tetrachloride, deuterated chloroform, CDClj and deuterated benzene C D, are often used. On the other hand if the sample is soluble only in polar solvents, deuterium oxide (D O), acetone -(CDjCOCDj), or dimethyl sulfoxide - [(003)280] are often employed. 

Exchanges of proton/deuterium in activated olefins like a-unsaturated arylsulfones and sulfoxides can be achieved either in deuterated solvent (acetonitrile or dimethyl sulfoxide d ) or in aprotic solvents in the presence of deuterated water [202,203]. The substitution process was found to be catalytic in electrons, and the reaction (fully regio-and stereoselective) could be elegantly followed [203] by H-NMR. In the following example (Scheme 36), the standard potential of the deutrated from is slightly more negative (40-50 mV) than the one of the starting sulfoxide, and radical anions could be involved in the chain process. 

Dimethyl Sulfoxide is well known as a solvent, with its deuterated form a commonly used material in NMR. All of the unsubstituted sulfoxides are readily... 

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... 

Several barley and wheat kernels and flour samples were used in the work presented in this chapter. The details concerning the plant material can be found in the relevant papers. The samples were prepared for NMR analysis by placing the kernel part (25-40 mg) or flour (app. 14 mg) in a 50 pi zirconia rotor (4.0 mm o.d.) followed by adding deuterated solvent (D2O or dimethyl sulfoxide (DMSO)) directly into the rotor. 5.8 mM 3-(trimethylsilyl)propionic acid-d4 sodium salt (TSP-d4) was added as chemical shift reference. 

It is popular to use non-deuterated solvents. In general, absorption lines are so broad that locking and shimming is of no siginifant value. It is more important to make sure that the sample can be heated up to 50-100 °C for line width reduction (see above). However, there may be a significant solvent dependence of the chemical shifts. For example, 5 values of H2O in various media are as follows [94Mae] +26.7 in HCl (11.3 M), +19.1 in pentane, -0.5 in dimethyl sulfoxide, -7.5 in pyridine, -11.7 in chloroform, -13.3... 

All modern NMR spectrometers operate in the pulsed Fourier transform (FT) mode for technical reasons, this means that deuterated solvents must be used. Deuterochloroform, CDCI3, is the most common such solvent, although a number of other, albeit generally more expensive, solvents such as acetone-d, (CDj)2CO, dimethyl sulfoxide-d, CD3SOCD3, and benzene-d, C D are also available. Deuterium oxide, D2O, may be used if the sample is water-soluble. 

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