Tetramethylsilane , as reference

Both were recorded over 5000 Hz range in deuterated dimethylsulphoxide on FT-80 A-80 MHz NMR spectrometer using tetramethylsilane as reference standard. The carbon chemical shift value are assigned on the basis of signal multiplicity, chemical shits and the comparison with the chemical shits of model compounds. 

Spectral Measurements. Infrared spectra of Nujol mulls of the complexes were obtained with a Beckman 1R5-A spectrophotometer. Ultraviolet and visible spectra were recorded on a Beckman DK-IA spectrophotometer. A Varian A-56/60 NMR spectrometer was used to measure the proton signals of solutions of OMPA, Mg (0104)2 3 OMPA, La(Cl04)3 4 OMPA, La(C104)3 3 OMPA 2 H2O, and (0104)3 3 OMPA 2 H2O in methylene chloride. The NMR measurements were made at 35 °0. with tetramethylsilane as reference. 

The 1H-NMR and 13C-NMR spectra of sulfacetamide in D2O were determined at 400 MHz and 75.4 MHz respectively on a Bruker AM-300 NMR spectrometer using TMS (tetramethylsilane) as reference standard and are shown in Figure 3-4. The spectral assignments are listed in Table III. 

FIGURE 13.7 The200-MHz H NMR spectrum of chloroform (HCCb). Chemical shifts are measured along the x-axis in parts per million (ppm) from tetramethylsilane as the reference, which is assigned a value of zero. 

All P.M.R. spectra were measured with a Varian HA 100 spectrometer operating in the frequency-sweep mode with tetramethylsilane as the reference for the internal lock. The double and triple resonance experiments were performed using a Hewlett Packard 200 CD audio-oscillator and a modified Hewlett Packard 200 AB audio-oscillator (vide infra). Spectra were measured using whichever sweep width was required to ensure adequate resolution of the multiplets under investigation, generally 250 or 100 Hz, and sweep rates were selected as necessary. Extensive use was made of the Difference 1 and Difference 2 calibration modes of the instrument, both for the decoupling experiments and for the calibration of normal spectra. 

To define the position of an absorption, the NMR chart is calibrated and a reference point is used. In practice, a small amount of tetramethylsilane [TMS (CH )4Si] Is added to the sample so that a reference absorption peak is produced when the spectrum is run. TMS is used as reference for both l H and 13C measurements because it produces in both a single peak that occurs upfield of other absorptions normally found in organic compounds. The ]H and 13C spectra of methyl acetate in Figure 13.3 have the l MS reference peak indicated. 

All solvents and reagents were reagent grade or were purified before use. IR spectra were recorded on a Perkin-Elmer 983 NMR spectra were recorded at 200 MHz on a Varian XL-200 using tetramethylsilane as an internal reference. Inherent viscosities were determined at a concentration of 0.5g/dL using a Canon-Fenske viscometer at 30°C. Monomer and polymer synthesis has recently been described (10). 

The 100 MHz pmr spectrum of a deutei> ochloroform solution containing tetramethylsilane as an internal reference was obtained on a Varian Associates XL-100-15 spectrometer equipped with a Nicolet pulsed Fourier accessory.32 (Figure 3.)... 

The H nuclear magnetic resonance spectrum of chlorpromazine hydrochloride in CDCI3 is shown in Figure 5 [13]. The data were recorded on a Varian XL 200 MHz spectrometer using tetramethylsilane as the internal reference. Assignments for the observed resonance bands are presented in Table 3. 

NMR characterization of the tautomers has shown that the pure keto isomer just above its melting point gives a single peak. This, of course, is required if structure assignment is correct. Absorption is at —2.67 ppm with reference to tetramethylsilane as an internal standard. This tautomer is extremely reactive and polymerized to an appreciable extent even at - 78° C in a few hours or in a few seconds at room temperature. 

The NMR spectrum of the pure enol in deuterochloroform solution at — 52° C contains three proton resonances. One is at —4.93 ppm for vinylic protons, a second at — 2.8 ppm for SH, and a third at —1.95 ppm for methyl protons, all with reference to tetramethylsilane as an internal standard. The pure enol tautomer is much less reactive than the thioketo form as it does not change appreciably after one hour at room temperature. It does undergo deep seated changes, however, when kept a few days at room temperature. 

We have used the VARIAN XL 100 (100 MHz), VARIAN DA 60 IL (60MHz) and CAMECA (350 MHz) as apparatus. The spectra have been obtained In deuterated chloroform at room temperature with tetramethylsilane as an Internal reference. We cannot work at elevated temperatures to reduce the broadening of the bands because polyacrolelns are very sensitive to heat. 

Chemical shifts are expressed in p.p.m. downfield from tetramethylsilane as internal reference, with... 

Measured in ppm from tetramethylsilane as an external reference. All spectra were run in mixed D2Q—D2SO4 solutions. The NH2 groups are deuterated in D20 alone. 

All spectra were recorded in deuteriochloroform at 60 Me with tetramethylsilane as standard.1 The numbers in parentheses refer to the number of hydrogen atoms, and the letters indicate the multiplicity s, singlet d, doublet t, triplet q, quadruplet, m, multiples In DjO, with external standard. 

The PMR spectrum of camphor in CDCI3 was recorded on a Varian T-60A, 60 MHz NMR spectrometer using TMS (Tetramethylsilane) as an internal reference (Fig. b). The following structural assignments have been made... 

The H-NMR spectra of chloroquine base and phosphate are shown in Fig. 5 and 6 and were obtained on Varian T6-A NMR Spectrometer with CDCI3 and D 0 respectively as solvents and tetramethylsilane as an internal reference. The signals are assigned in Table 2. 

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). 

Fig. 19. NMR spectra of solutions of methyl methacrylate-styrene copolymers and homopolymers, 0.10 g. in 0.5 ml. of CHClj or CCl (see text) with 2% tetramethylsilane as internal reference (r = 10.00) (a) polystyrene ( )10 90 (methyl methacrylate styrene mole ratio in monomer feed) (c) 25 75 [d) 50 50 e) 75 25 (/) 90 10 ...

Proton magnetic resonance (PMR) spectra were recorded on a Varian A 60A spectrometer using ordinary chloroform as solvent and tetramethylsilane as internal reference. Melting points were not corrected. 

The NMR spectrum of pure pymvic acid consists of two resonances—one due to the carboxyl proton at 8.67 ppm and another due to methyl protons at 2.55 ppm (relative to tetramethylsilane as the reference). The separation between these two peaks is dependent on the purity of the sample— the greater the purity, the greater is the separation. Taking the spectmm of pymvic acid will allow a qualitative check on sample purity and will also provide practice with shinuning a sample for optimal resolution (narrow lines). 

Figure 13.5 The NMR chart. The downfield, deshielded side is on the left, and the upfield, shielded side is on the right. The tetramethylsilane (TMS) absorption is used as reference point.

Tetramethylsilane (Section 14. IB) An internal standard used as a reference in NMR spectroscopy. The tetramethylsilane (TMS) reference peak occurs at 0 ppm on the 5 scale. 

In a zeolite, where the framework comprises TO4 tetrahedra (T silicon or aluminium), the chemical shift of the silicon, compared to tetramethylsilane adopted as reference, varies with the number of aluminium atoms located in the second co-ordination sphere (cf. Fig. 13.6). From the NMR spectrum, it is possible to obtain the concentration of each of these configurations and, by applying Lowenstein s rule (no Al-O-AI links), calculate the atomic Si/Al ratio of the framework using the formula ... 

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