Chemical shift internal reference

Chemical shift (p.p.m.) of model compounds in H20 relative to internal 1,4-dioxane (67.86 p.p.m.). Chemical shifts for these compounds are given at pH 5.5-7.5. Estimated precision for the chemical shifts is 0.05 p.p.m.h See Refs. 82 and 83. See Ref. 20.d These assignments may have to be interchanged. See Ref. 21 numbers in the brackets below the given chemical shift values refer to those published in Ref. 86. f See Ref. 19. The chemical shift for the -anomeric carbon atom was found to be 100.6 p.p.m. and was determined from an anomeric mixture of this compound. The existence of the a-Man — Ser unit was confirmed by the l]CH value (169 Hz) obtained for this compound. See Ref. 84. 

Chemical shifts are expressed in S units ppm of applied magnetic field with internal TMS peak as reference. 

Chemical shifts expressed in p.p.m. referred to internal MeN02. 

The proton NMR spectrum of griseofulvin (Figure 2) was obtained in DMSO-d, solution (cone, w/v = 10 mg/0.40 ml) containing TMS as internal reference utilizing the Varian Associates CFT-20 Spectrometer operating at a frequency of 79.5 MHz. The chemical shifts (<5, ppm) are with reference to TMS. The experimental conditions are ... 

The carbon-13 NMR spectrum of griseofulvin (Figure 3) was obtained at ambient temperature in DMSO-d containing TMS as internal reference utilizing Varian Associates XL-100-15 spectrometer equipped with Fourier accessories The system was locked to the deuterium resonance frequency of the solvent, and operated at a frequency of 25.2 MHz for carbon-13. The chemical shifts are reported ( c, ppm.) from the Internal standard TMS. 

NMR spectra were recorded on Bruker AC200 spectrometers unless indicated otherwise deuteriated chloroform was used as solvent and tetramethylsi-lane as internal reference. Chemical shifts (8) are given in ppm. The following abbreviations were used to define the multiplicities s, singlet d, doublet t, triplet q, quartet m, multiplet br, broad coupling constants (/) are measured in Hertz (Hz). IR spectra were recorded on a Nicolet Magna-550 FTIR... 

IR spectra were taken on an Analect RFX-30 FTIR spectrophotometer neat between NaCI or KBr plates or as KBr disks. 1H NMR spectra were recorded on a Nicolet NT-360 (360 MHz) or on a Varian VXR-200 (200 MHz) spectrometer. All chemical shifts are reported in parts per million (8) downfield from internal tetramethylsilane. Fully decoupled 13C NMR spectra and DEPT experiments were recorded on a Varian VXR-200 (50 MHz) spectrometer. The center peak of CDCI3 (77.0 ppm) was used as the internal reference. 

Fig. 1. Relationship between F CF3 chemical shifts of S-, Se-, and 7e-(trifluoromethyl)-dibenzothiophenium, -selenophenium, and -tellurophenium triflates and Hammett s constants Om or (Tp for the ring substituents S, Se, and Te refer to substituted and unsubstituted S-, Se-, and Te-(trifluoromethyl)dibenzothiophenium, -selenophenium, and -tellurophenium triflates, respectively. The numbers on the lines are the compound numbers shown in the text. Substituents and their substitution positions are shown in the parentheses. The smaller the F NMR chemical shift is, the more downfield is the resonance (CFCI3 served as an internal standard in CD3CN).

The proton noise-decoupled 13c-nmr spectra were obtained on a Bruker WH-90 Fourier transform spectrometer operating at 22.63 MHz. The other spectrometer systems used were a Bruker Model HFX-90 and a Varian XL-100. Tetramethylsilane (TMS) was used as internal reference, and all chemical shifts are reported downfield from TMS. Field-frequency stabilization was maintained by deuterium lock on external or internal perdeuterated nitromethane. Quantitative spectral intensities were obtained by gated decoupling and a pulse delay of 10 seconds. Accumulation of 1000 pulses with phase alternating pulse sequence was generally used. For "relative" spectral intensities no pulse delay was used, and accumulation of 200 pulses was found to give adequate signal-to-noise ratios for quantitative data collection. 

Fig. 7 Mobility-shift assay for the determination of dissociation constant of the complex between anti-DNP rat monoclonal IgG21) antibody and charged ligands that contained the A-dinitrophenyl group. Mesityl oxide (MO) served as EOF marker, bovine carbonic anhydrase (CAB) and bovine a-lactalbumin (LA) as internal references. The DNP ligands with a charge of —1 (A) und —9 (B), respectively, were used as additives to the running buffer. (Reprinted with permission from Ref. 30. Copyright 1995 American Chemical Society.)...

IH and 13C NMR spectra were recorded on a Bmcker AM-200 and 500MHz) chemical shifts are given in d values referred to internal tetramethlysilane (TMS), EIMS (MS Agilent 5973 70eV) and Infrared (IV) spectra were recorded on a Nicolet spectrophotometer with Fourier transform Model Magna-IR 760 wavelengths are expressed in reciprocal centimeter (cm ). 

For quantitative estimation, a sealed reusable capillary tube, with a known quantity of sodium salt of trimethylsilyl propionic acid (TSP) dissolved in 35 pi of D20, is inserted into the NMR tube while obtaining NMR spectra. The internal standard TSP is used as a chemical shift reference as well as a quantitative standard for the estimation of metabolites, and D20 is used as the field-frequency-lock . Spectra are acquired at room temperature. Typical spectra acquired at room temperature of human bile and standard glycine- and taurine-conjugated BAs are shown in Fig. 5.4.16. 

Figure 4. The eight-pulse line shape and the peak locations of the Th4Hi5 (LP) powder sample as a function of temperature using a Ca(OH)2 single crystal as reference. The reference is oriented such that the major principal axis of the proton chemical shift tensor is parallel to the external magnetic field. A shift to the left signifies an increase in the value of

Some other data on, 5N chemical shifts, referred to internal MeN02, are recorded in Table 25. Comparison of pyrrole with imidazole demonstrates that the deshielding of the pyrrole-type nitrogen is about 15 ppm. Increased nitrogen shielding is observed for 2,1,3-benzothiadiazole ( + 49 ppm) and the parent 1,2,5-thiadiazole ( + 34 ppm). In contrast, the corresponding oxadiazoles were deshielded, as in 2,1,3-benzooxadiazole ( — 36 ppm) and 1,2,5-oxadiazole (— 34 ppm). 

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. 

In essence, the chemical shift of a nucleus such as proton ( I I) is its resonance frequency. It is usually expressed in parts per million (ppm) relative to a standard. The most common standard is tetramethylsilane [(CH3)4Si, TMS] which defines 0 on the delta (8) scale and 10 on the older, less used t scale. A small amount of TMS is typically added to the NMR solution to be examined. The presence of an internal standard minimizes experimental variations. This is particularly important because the chemical shift is typically a change of only a few hertz per megahertz, hence the part per million (ppm) scale. The separation of peaks will be greater in hertz at higher field but spectra obtained at different field strengths are comparable on the ppm scale. Common reference standards are listed in Table 6.32. 

The broad band decoupled carbon-13 NMR spectrum of cimetidine hydrochloride (Figure 3) was obtained by using a solution of approximately 100 mg/ml in deuterated dimethylsulf oxide. The deuterium signal of dimethylsulfoxide was used as the internal reference and the spectrum was obtained on a Varian Associates Model FT-80 fourier transform NMR spectrometer. The chemical shift assignments are ... 

The C NMR spectrum of oxyphenbutazone in acetone-dg using TMS as an internal reference was obtained using a Jeol FX 100 MHz Spectrometer at an ambient temperature using 10 mm sample and is presented in Figure 4. The carbon chemical shift values are derived from the off-resonance spectrum and are listed below. The results are consistent with those reported earlier (5). 

The proton NMR spectrum was recorded in DMSO-dg containing tetramethylsilane as internal reference and with the use of a Bruker WM-300 spectrometer at frequency 300.13 MHz. The spectrum is presented in Figure 2 and the spectral assignments are summarized in Table II (11). The chemical shifts roughly agree with those reported for sulfadiazine (12). The change in chemical shifts (to high field) for silver sulfadiazine compared to sulfadiazine is 0.3 ppm (NH2) or less (11). 

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