High-resolution proton NMR spectra

Figure 3. High resolution proton NMR spectra of cheese, obtained by application of a Hahn spin echo pulse sequence with and without field gradient pulses. Measurements were performed on a Bruker MSL-300 spectrometer, operating at 300 MHz. The field gradient unit used with this spectrometer was home-built and the strength was calibrated to 0.25 T/m, using a 1-octanol sample for which the diffusion coefficient is known at several temperatures.

High Resolution Proton NMR Spectra of Blood-Group Active Glycosphingolipids in DMSO-dl... 

The solute molecule is dissolved in the liquid crystal solvent at low concentration. A variety of nematic solvents are available, some of which are nematic at room temperature. Representative high-resolution proton NMR spectra are given in Figure 1. Because the solvent order depends on composition and temperature, it is important that temperature and composition gradients at the NMR probe be minimized if the narrow line widths of a few hertz are to be obtained. The spectra of Figure 1 show the rapid increase of spectral complexity with the number of nuclei. The spectra become almost continuous and uninterpretable at about 10 spins. Simplified proton NMR spectra can be obtained by partial deuterium substitution and decoupling.6 This has been described for cyclohexane, but has not been used extensively. Proton double resonance is also a useful experimental technique for the identification of spectral lines.6... 

The infrared spectra of the coal and the various extracts were recorded on a Baird, Model GY-1 (Ireland Mine vitrain concentrate) and on a Perkin Elmer Model 337 spectrophotometer (Bruceton coal). The samples were prepared by the potassium bromide pellet technique. The high resolution proton NMR spectrum of the benzene soluble extract from Ireland Mine vitrain concentrate was recorded on a Varian A-60 spectrometer in 10% deuterated chloroform (CDCh) solution, using tetrametnylsilane internal standard. 

Lyerla et al. measured Tic over a wide temperature range from room temperature down to 105 K [94], and concluded that Tic s of not only CH3 but also CH resonances depend on CH3 rotational motion, and that the broadening of the CH3 resonance below -100 °C is also due to modulation of CH3 rotational motion at the frequency of proton nutation in the presence of the decoupling field. Gomez et al. have also reported solid-state high-resolution 13C NMR spectra of isotactic polypropylenes [95]. They used samples characterized by X-ray crystallography and reconfirmed the results obtained by Bunn et al. 

Fig. 6.1.9. 200 MHz spectra of H pertaining to spin diffusion experiments on a nylon 6,6 PBZT blend (VanderHart [46]). Left, magnetization gradient created by dipolar echo sequence with spacing 30 [xs, thus, initially favoring the PBZT portion of the blend. Right, results of spin diffusion observed using CRAMPS to obtain high resolution proton NMR of the blend, and observation of magnetization transfer between the phenyl protons of the PBZT, and the methylene protons of the nylon 6,6.

A Varian XLFT-100 Fourier Transform nmr Spectrometer interfaced with a Varian 620-L minicomputer with magnetic tape storage provided high-resolution, proton-decoupled spectra of natural abundance carbon-13 at 25.2 MHz. For identification of carbon peaks, chloroform-d solutions of surfactant (solubility about 20 wt%) were prepared. Chloroform-d also served for a deuterium field lock. Samples of surfactant in water or decane were placed... 

As mentioned earlier, the high-resolution H NMR spectra recorded here for static samples are linked to mobile water molecules but the dc relaxation (TSDC) is caused by mobile protons and other ions when condition of throughout percolation of ions (between two electrodes in a TSDC cell) is achieved on heating of a frozen system. Both dynamic phenomena are temperature dependent (Figure 1.210). 

Figure 24.5 The High-Resolution Proton NMR Spectrum of 2-Propanol Dissolved in Deuterated Chloroform. From Charles J. Pouchert and John R. Campbell, The Aldrich Library of NMR Spectra, The A dr ch Chemical Co., 1974, Vol. I, p. 85.

High-resolution proton NMR spectroscopy can be used to obtain an overview on the phase behavior. The hnewidth and the presence or absence of peaks provides information on the dynamic state of the chain molecules. As an example, the proton spectra of the different samples of SDS/CA/D2O obtained at 30 and 70 °C, which are shown in Fig. 4, are discussed [19]. The signal of D2O, which has a temperature dependent resonance frequency, was used as lock signal and chemical shift reference. Therefore the other signals have temperature-dependent chemical shifts. The signal intensities of all spectra are scaled to obtain equal heights of the large CH2 peaks, which occur at about 1.3 and 1.7 ppm in the spectra at 30 and 70 °C, respectively. 

Fig. 6 H NMR spectra obtained with a prototype of a rheo-NMR probe for proton measurements. Top and center. Spectra of samples J9 (micellar solution) and J1 (gel) in comparison with high resolution H NMR spectra. Bottom Spectra of sample J1 at 40 and 70 °C. Despite the poor resolution of the rheo-probe and a background signal from the coil support made of Teflon the difference between rigid and fluid alkyl chains can be clearly recognized...

High-resolution proton NMR spectroscopy can furnish valuable information about the chemical structure, regiochemistry, stereochemistry, and conformation of a polymer. Model compounds are helpful for assigning peaks in the NMR spectra of polymers. Although data from the monomer and dimer models can be presumed to be transferable to the polymers, some unique features in the proton spectra of the polymers can give insight into the polymer structure. 

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