Tetramethylsilane internal reference

The zirconium and hafnium complexes of trifluoroacetyl-acetone are white crystalline solids, insoluble in water but soluble in benzene, cyclohexane, and carbon tetrachloride. The hafnium complex melts at 128 to 129° and the zirconium complex at 130 to 131°. The complexes have been subjected to gas-phase chromatography and may be sublimed at 115° at a pressure of 0.05 mm. The proton magnetic resonance spectra of the compounds dissolved in carbon tetrachloride show single peaks in the methyl and methylene regions. The peaks appear at 2.20 and 6.00 p.p.m. (5) relative to tetramethylsilane (internal reference) for the zirconium complex and at 2.20 and 5.97 p.p.m. for the hafnium complex. 

The infrared spectrum (Nujol and KBr) shows characteristic absorptions for coordinated BH3 in the region 2260-2400 cm.-1 for B—H stretch, and 1165 cm.-1 for B—H bend. The proton n.m.r. spectrum in dichloromethane gives a doublet (J = 6 Hz.) for the methyl protons at 2.50 p.p.m. down field from tetramethylsilane (internal reference). The protons attached to the boron are observed as a symmetrical quartet, as expected for BH3 adducts three peaks... 

Chemical shifts are quoted in t units (deuteriochloroform) downfield from the tetramethylsilane internal reference. All resonances are singlets unless stated otherwise. 

Figure 2. NMR Spectrum Isopropamide, SK+F standard SJB- 6-226a in deuterochloroform tetramethylsilane internal reference, Instrument JEOL C 60 H.

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.)... 

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. 

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. 

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. 

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... 

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). 

Samples for 13C NMR spectrometry are usually dissolved in CDC13, and the 13C peak of tetramethylsilane (TMS) is used as the internal reference. A list of the common deuterated solvents is given in Appendix A. 

Carbon-13 chemical-shifts are defined relative to the carbon signal of internal tetramethylsilane (Me4Si) hence, when measuring spectra in organic solvents, Me4Si should be added to the sample solution as the internal reference-standard.23 However, any homo- or hetero-nu-clear signal of the solvent, or of an added reference compound, may be used to calculate the 13C-chemical shifts, provided that its shift rela-... 

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 ...

Tetramethylsilane became the established internal reference compound for H NMR because it has a strong, sharp resonance line from its 12 protons, with a chemical shift at low resonance frequency relative to almost all other H resonances. Thus, addition of TMS usually does not interfere with other resonances. Moreover, TMS is quite volatile, hence may easily be removed if recovery of the sample is required. TMS is soluble in most organic solvents but has very low solubility in water and is not generally used as an internal reference in aqueous solutions. Other substances with references close to that of TMS have been employed, and the methyl proton resonance of 2,2-dimethylsilapentane-5-sulfonic acid (DSS) at low concentration has emerged as the reference recommended by IUPAC for aqueous solutions.55 Careful measurements of the DSS-TMS chemical shift difference when both materials are dissolved at low concentration in the same solvent have shown that for DSS 5 = + 0.0173 ppm in water, and 8 = — 0.0246 ppm in dimethyl sulfoxide. Thus, for most purposes, values of 8 measured with respect to TMS or DSS can be used interchangeably. 

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. 

Tetramethylsilane in DMSOdg and terf-butanol in water as internal references. Temperature coefficient, ppm to a higher field per degree. 

H NMR spectra were recorded on a Bruker AC 400 spectrometer with tetramethylsilane (TMS) as internal reference. Infrared spectra were obtained as KBr pellets on a Perkin-Elmer 580 B FT-IR spectrometer. Electrospray (ES) mass spectra were recorded on an LCQ Finnigan Mat spectrometer. The excitation and emission spectra were obtained on a SPEX FL-2T2 spectrofluorimeter with slit at 0.8 mm and equipped with a 450 W lamp as the excitation source. Luminescence lifetimes were measured with a SPEX 1934D phosphorimeter using a 7 W xenon lamp as the excitation source with the pulse width at 3 ps. Powder X-ray diffraction patterns were recorded on Rigaku D/Max-IIB diffractometer using Cu-Ka radiation. 

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. 

The NMR spectrum shown in Figure 2 was obtained by dissolving 49.9 mg chlordiazepoxide hydrochloride in 0.5 ml of DMSO-dg containing tetramethylsilane as internal reference. The spectral assignments are shown in Table I . NMR studies by Nuhn and Bley at 100 MHz and various temperatures indicate that the methylene protons at position three are not equivalent4. 

The nuclear magnetic resonance (NMR) spectrum (Fig. 2) was obtained by preparing a saturated solution of meperidine hydrochloride, U.S.P. (Wyeth Lot No. F-665901) in deutero chloroform containing tetramethylsilane as internal reference. The only exchangeable proton is the hydrogen associated with HC1. The NMR proton spectral assignments are given in Table II. 

The NMR spectrum of triamcinolone, dissolved in deuterodimethyIsulfoxide containing tetramethylsilane as an internal reference, shows the presence of the cross conjugated dienone, C-l proton resonance at 2.74 T (doublet, Ji 2 = 10 Hz), C-2 proton resonance at 3.80 t(quartet, J2 4 =... 

Fig.3 NMR spectrum of triamcinolone, Squibb House Standard 30197-503 in deuterodimethylsulfoxide containing tetramethylsilane as internal reference. Instrument Varian A-60...

Fig. 3 NMR Spectrum of Triamcinolone Diacetate. House Standard 30636-001 in DMSO containing tetramethylsilane as internal reference.

The n.m.r. spectra were obtained by using a Bruker WM-250 multinuclei Fourier transform spectrometer. Typical anion solutions were approximately 0.2 M, and the probe temperature was 25 °C. The chemical shifts are with reference to tetramethylsilane. For the carbon-13 measurements a small amount of cyclohexane was added to the carbanion solution as an internal reference using S(SiMe4) = S(cyclohexane) + 27.7 p.p.m. b One bond I3C— H coupling constants.c Huckei j>charges... 

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