Deuterochloroform

The aim of the first example is to look for polychlorinated biphenyls (PCB) for which C-NMR spectra, measured in deuterochloroform, as well as the partition coefficients between 1-octanol and water arc known. Since it is not reliable to per-... 

Deuteroacetone, internal tetramethylsilane. Values in deuterochloroform can be found in Ref. 64,... 

In deuterochloroform, pyrazine shows a single proton resonance at S 8.59 (72CPB2204). Vo, Vm and Vp values between pyrazine ring protons obtained from a number of pyrazine derivatives are 2.5-3, 1.1-1.4 and 0 Hz respectively, and these values do not appear to be affected by the nature of the ring substituents. Some substituent shielding parameters are shown in Table 1. 

Telluradiazolines are thermally stable crystal compounds, but they are very sensitive to light. When exposed to daylight, telluradiazolines undergo rapid decomposition, even in the solid state. By heating degassed solutions of telluradiazoline 79a in deuterochloroform or benzene, telluroketone 85 and alkenes 81 and 82 are formed in almost quantitative yield (93JA7019). 

The only known representative of this type of compound, 91, was prepared by 1,3-dipolar addition of mesityl nitrile oxide to telluroketone 85 (93JA7019 94MI1). The reaction proceeds smoothly on heating equimolar amounts of the reactants at 80°C, giving rise to 91 in 70% yield. The heterocycle is a thermally unstable and light-sensitive compound. Thermolysis of a deuterochloroform solution of 91 at 60-90°C in a sealed ampule affords 1,1,3,3-tetramethylindanone and mesityl isonitrile (94MI1). 

Figure 1. Part of NMR spectrum of 5-deoxy-l, 2-O-iso-propylidene-3-O-tosyl-p-L-threo-pent-4-enofuranose (32) at 60 Mc.p.s. in deuterochloroform.

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... 

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. 

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. 

Broadband proton-decoupled pulse Fourier transform C n.m.r. were recorded in deuterochloroform at 20 MHz using a Varian CFT-20 spectrometer. 

Figure 9 1,/i-ADEQUATE spectrum of strychnine (1) optimized for 5 Hz. The data were acquired using a sample of 1.8 mg in 40 j.Lof deuterochloroform in a 1.7-mm NMR tube at 600 MHz using a 1.7-mm Micro CryoProbe. The data were acquired as IK x 160 points with 320 transients/q increment and a 3-s interpulse delay giving an acquisition time of 48 h 17 min. The data were linear predicted to IK points in the first dimension and from 160 to 512 point in the second frequency domain followed by zero-filling to give a final IK x IK data matrix. 

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. 

Determined by hexadeuterodimethyl sulfoxide unless stated otherwise. Determined in deuterochloroform. c Determined in D20. 

Figure 4 is the 100 MHz NMR Spectrum of halcinonide in deuterochloroform containing tetramethyl-silane as internal reference at 0 Hz. The instrument used is a Varlan Associates, Inc., Model XL-100 NMR spectrometer. Below is an interpretation of the various resonances. ... 

Referenced from center peak of deuterochloroform = 77.0 ppm from tetramethyl silane. Numbers in parentheses refer to alternative assignments (see text for details). 

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). 

---