Solvents deuterochloroform

We have used only two different solvents, deuterochloroform (CDC13) and hexadeuterodimethylsulfoxide (DMSO-d6). The former dissolves a large majority of organic molecules, but DMSO must be used for more polar substances. The disadvantage of DMSO is that it is very hygroscopic, so that even if you try hard to keep it dry you may find small signals due to water in your spectra. Look out for these in the spectra in this book they normally he at about 3.3 ppm. 

Fig. 2 NMR Spectrum of Meperidine Hydrochloride, U.S.P., Wyeth Lot No. F-665901. Solvent deuterochloroform, internal standard tetramethyl-silane. Instrument Jelco Model C-60 HL.

Figure 2. NMR Spectrum of Propiomazine Hydrochloride (N.F. Reference Standard Material) Solvent deuterochloroform, internal standard tetramethylsilane Instrument Jeolco Model C-60 HL...

Irganox 1076 [octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,6-di-t-butyl-4-methylphenol and diisooctyl phthalate were analyzed by GPC interfaced with both electrospray mass spectrometry (ESI-MS) and NMR.1 A deuterochloroform solvent was used. It was noted that a parallel arrangement was necessary to avoid backpressure on the NMR flow-probe that can... 

However, NMR spectrometers use deuterium signals from deuterium-labelled molecules to keep them stable such substances are known as lock substances and are generally used in the form of solvents, the most common being deuterochloroform CDC13. 

Polymer Characterization. Proton NMR spectra at 300 MHz were obtained from a Varian HR-300 NMR spectrometer. Deutero-benzene and spectrograde carbon tetrachloride were used as solvents. The concentration of the polymer solutions was about 1-5%, Carbon-13 NMR spectra were obtained from a Varian CFT-20 NMR spectrometer, using deuterochloroform as the solvent for the polymers. The concentration of the solutions was about 5%. Chemical shifts in both proton and carbon-13 spectra were measured in ppm with respect to reference tetramethylsilane (TMS). All spectra were recorded at ambient temperature. 

The NMR spectrum shown in Figure 5 was obtained by dissolving hydralazine hydrochloride in deuterium oxide containing 3-(trimethylsilyl)-1-propane-sulfonic acid sodium salt (DSS). The series of peaks at 0, 0.6, 1.8, and 3 ppm are all due to the DSS. The peak at 4.8 ppm is due to HDO which forms on exchange with the solvent and the peaks at 8.01 and 8.61 ppm are due to the aromatic protons. The NMR spectrum of the base (Figure 6) was obtained in a 1 1 mixture of dimethylsulfoxide-d,- deuterochloroform. 

Because most common solvents, including water, contain protons, and most NMR analyses involve the measurement of protons, a solvent without protons is generally used in NMR spectroscopy. Commonly, solvents in which the hydrogen atoms are replaced with deuterium (i.e., solvents that have been deuterated) are used, the most common being deuterochloroform. In addition, an internal standard, most commonly tetramethylsilane (TMS), is added to the sample in the NMR sample tube (see Figure 14.3, D) and all absorption features are recorded relative to the absorption due to TMS. 

A compound for NMR spectroscopy must be a liquid or solid which can be put in a solution. The usual solvents are deuterochloroform (CDC13), deuteroacetone (CD3-CO-CD3) or deuterium oxide (D20). 

The most commonly used organic solvent is deuterochloroform, CDCI3, which is an excellent solvent and is only weakly associated with most organic substrates. CDCI3 contains no protons and has a deuterium atom. For ionic compounds or hydrophilic compounds, the most common solvent is deuterated water, D2O. 

Poly(ethyl methacrylate) (Cellomer Associates) was vacuum dried at 50 C. The molecular weight (M ) was determined to be 3.3 X 10 from its intrinsic viscosity in ethyl acetate.— Chloroform (spectral grade) and deuterochloroform (MSD Isotopes) were used as received. Prior to sample preparation the solvent was degassed using five freeze-thaw cycles. The solvent was vacuum distilled onto the polymer In a 12 nm NMR tube, and sealed. 

The most frequently used NMR solvents for flavonoid analyses are hexadeuterodimethylsulf-oxide (DMSO-J6) and tetradeuteromethanol (CD3OD). Anthocyanins require the addition of an acid to ensure conversion to the flavylium form. For the analysis of relatively nonpolar flavonoids, solvents such as hexadeuteroacetone (acetone-J6), deuterochloroform (CDCI3), carbontetrachloride (CCI4), and pentadeuteropyridine have found some application. The choice of NMR solvent may depend on the solubility of the analyte, the temperature of the NMR experiments, solvent viscosity, and how easily the flavonoid can be recovered from the solvent after analysis. In recent years, the problem of overlap of solvent signals with key portions of the NMR spectrum has been reduced by solvent suppression and the application of improved 2D and 3D NMR techniques. 

Prototropic tautomerism of 2-alkylated tetrahydro species 21 is solvent dependent, tautomers 21a and 21b being identified as the major species present in DMSO-dimethyl sulfoxide) and deuterochloroform, respectively <2000HCA1693> by NOE experiments. Acetylated analogue 22 appears to behave similarly, although in this case the spectrum is complicated by the presence of amide rotamers. As judged from the N-H signals observed in H NMR spectrum, the major species in deuterochloroform is 22a, whereas, in DMSO-i4> the tautomeric equilibrium constant approaches unity, and both tautomers are present. 

The proton NMR spectrum of 1,10-phenanthroline has been obtained and analyzed by several authors in nonaqueous solvents 04-109 and in water at various pH values.28,110 Examples of studies of the NMR spectra of substituted 1,10-phenanthrolines that have been investigated in some detail are also worthy of mention.47,104,106,11° The NMR spectra of all ten phenanthrolines have been determined in deuterochloroform, and the spectra were interpreted12 (Table IV). The spectra of the 1,7-, 1,10-, and 4,7-isomers have also been compared with that of phenanthrene.111 Shifts in the NMR spectrum of 1,10-phenanthroline induced by a europium shift reagent have been discussed,112 and 13C chemical shifts of free and protonated 1,10-phenanthroline were measured.113... 

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]... 

Procedures. Spectra were obtained on a Varian A-60 NMR spectrometer. Lignin samples and model compounds were analyzed as 16% solutions in deuterochloroform solvent using a tetramethylsilane internal standard. 

The 119Sn chemical shift of dimethyltin dichloride in carbon tetrachloride and other non-polar solvents remains practically invariant to large changes in concentration. It has a value of ca. +140 ppm. This indicates the ease with which the molecules are able to dissociate into discrete tetrahedral species in solution as a result of the very weak inter-molecular Sn... Cl bonds which exist in crystalline dimethyltin dichloride. (55) On the other hand, a chemical shift-concentration study of trimethyltin formate in deuterochloroform solution (56) has revealed a dramatic change in chemical shift from +2-5 ppm for a 3 M solution to + 152 ppm on dilution to 0-05 m in the same solvent. This has been attributed to self-association of monomeric tetrahedral trimethyltin formate molecules, [3]. As the concentration is increased, five-coordinate oligomeric or polymeric species, [4], could be formed. These are known to exist in the solid state. (57)... 

Proton NMR spectra are generally recorded in solution in deuterochloroform (CDCI3)-—that is, chloroform with the H replaced by 2H. The proportionality of the size of the peak to the number of protons tells you why if you ran a spectrum in CHCl3) you would see a vast peak for all the solvent Hs because there would be much more solvent than the compound you wanted to look at. Using CDCI3 cuts out all extraneous protons. 

Deuterochloroform solutions seem to yield slightly higher (ca. 0.5 kcal/mole) barriers than solutions in hydrocarbon solvents (see for instance 111, 139 83)). 

Deuterochloroform (CDCI3) is one of the most widely used nmr solvents. Although more expensive than nondeuterated solvents, it will dissolve a wider range of samples than carbon disulfide or carbon tetrachloride. Residual protons in the CDCI3 will always give a peak at 7.27 ppm. Chemical shifts of protons are measured relative to the sharp peak of the protons in tetramethylsilane (taken-as 0,0 ppm). Stock solutions of 3-5% tetramethylsilane in carbon disulfide and in deuterochloroform are useful for preparing routine samples. 

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