2H NMR spectrum

Fig. 5a-c. Theoretical 2H NMR spectra in the rapid exchange limit for the motional mechanisms depicted schematically in Fig. 4 a Kink-3-bond motion b crankshaft-S-bond motion c 180° jump of phenyl ring... 

Fig. 14.2H NMR spectra of LPE, isothermally crystallized from the melt at 396 K (Mw as 100000, Mw/Mn as 10, Merck, Darmstadt) at 55 MHz obtained from a complex FT of the solid echo for various temperatures...

Fig. 28. Room temperature 2H NMR spectra of the smectic liquid crystalline polymer (m = 6), oriented in its nematic phase by the magnetic field (8.5 T) of the NMR spectrometer with director ii parallel (left) and perpendicular (right) to the magnetic field...

Fig. 29. Observed and calculated 2H NMR spectra for the mesogenic groups of a) the nematic (m = 2), b) the smectic (m = 6) liquid crystalline polymer in the glassy state, showing the line shape changes due to the freezing of the jump motion of the labelled phenyl ring. The exchange frequency corresponds to the centre of the distribution of correlation times. Note that the order parameters are different, S = 0.65 in the frozen nematic, and S = 0.85 in the frozen smectic system, respectively...

Fig. 2.8.12 2H NMR spectra obtained at the stress is highest, a quadrupole splitting is...

Fig. 2.8.17 Director orientation 0 obtained from 2H NMR spectra from the polysiloxane backbone polymer with liquid-crystal side-chain 4-methoxyphenyl-4 -butenyloxybenzoate, as a function of the apparent extension rate, i. The...

H NMR and 2H NMR spectra of fractionated coal products from El0 and El9 were recorded and analyzed to determine and 2H composition for each structural position. In our study, y y and 2Hx,v are defined as the fraction of the JH and 2H determined from the integrals of the NMR spectra of a given soluble fraction where y equals HS, BS or BMS and x = y-alkyl, 0-alkyl, a-alkyl or aromatic structural positions. The spectral range of the NMR integrations are given in Table V. 

The new results described are from the work of graduate students S.M. Ling (a-elimination) and J.T. Burton (ring expansion). We thank NSERC (Canada) for financial support. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support. We thank Dr. J.B. Stothers for the 13C and 2H NMR spectra. 

Static 2H NMR spectra suffer from low sensitivity, as resonances are spread continuously over the 200 kHz range. In samples with multiple sites, they also lack resolution. However, both shortcomings can be remedied by using MAS. As was shown in Sect. 2.3.3, in a rigid sample MAS averages out the inhomogeneous first-order quadrupolar broadening in the same way as it eliminates the CSA in... 

It will be useful to outline the basic features of solid state 2H NMR spectra. Deuteron is a spin 7= 1 nucleus possessing an electric quadrupole moment. The EFG interacts with the electric quadrupole moment to produce a frequency shift. Frequencies of the symmetric line shape centred around the Larmor frequency >0, which depend on the relative orientation of an external magnetic field B0 and the EFG tensor, are given by1 7... 

H NMR spectra are profoundly influenced by motions.1 7 It is possible to calculate the powder spectra in the presence of any type of motion by taking into account the geometry, and amplitudes and rates of motions involved.80,81 Consider a C-2H bond which can jump between three equivalent sites,... 

Fig. 3. Calculated 2H NMR spectra for a phenyl ring (left) and a methyl group (right) as a function of jump rate.

Fig. 28. 2H NMR spectra of PBLG-d5 (a) and PBG-d5 (b) as a function of temperature. Reproduced with permission from Elsevier Science.

Simple 2H NMR spectra that can be readily interpreted are observed when the uniaxially oriented sample is aligned with its normal parallel to the spectrometer magnetic field... 

FIGURE 42. 2H NMR spectra from three different bR samples containing retinals with the individually deuterium-labeled methyl groups C18, C19 and C20. Reprinted with permission from Reference 57. Copyright (1994) American Chemical Society... 

The analysis of a full tilt series of 2H NMR spectra not only allows the determination of the unique bond angle for a deuteriated methyl group, but also provides an internal check for the consistency of the spectral interpretation. In particular, simulations provide a means for the analysis of line-broadening effects, which arise from the sample mosaic spread as well as the intrinsic line width of the nuclear transition and instrumental factors. When line shapes are fitted to a full tilt series of spectra in a concerted manner and are also compared with the powder spectrum of an unoriented sample, the different contributions can be discerned. In that way an intrinsic line width of around 2 kHz is found for the spectra shown here, together with a mosaic spread between 8° and 10° for the three samples. 

FIGURE 44. Tilt series of 2H NMR spectra from the deuteriomethyl groups Cl 8 (left column) and C20 (right column) of retinal in oriented purple membranes, at seven different sample inclination (a) in the spectrometer field. The line-shape simulations are superimposed over the experimental spectra in order to illustrate the good line fit obtained by the prediction method. Reprinted with permission from Reference 57. Copyright (1994) American Chemical Society... 

Figure 48 shows representative experimental 2H NMR spectra from the labeled retinal in bR in a dark-adapted PM sample. The line shape simulations that were generated in the data analysis are superimposed on the experimental spectra. The powder pattern [Figure 48(a)] serves as a general reference for the tilt series of spectra recorded at various sample inclinations [Figure 48(b)], because it defines the accessible frequency region over which the spectral intensity can occur. The oriented sample was measured at every 22.5° between 0° and 90°, of which three inclinations are represented in Figure 48(b) with a = 0°, 45° and 90°. 

FIGURE 48. Representative 2H NMR spectra (full lines) of dark-adapted bR (90 mg) containing deuteriated retinal, with line shape simulations (dashed lines) superimposed. Both the powder spectrum (a) from randomly oriented PM patches and the tilt series (b) over sample inclinations, a = 0, 45° and 90°, were recorded at — 60 °C (number of scans, 1.7 x 105, for a = 0°). Spectrum (c) was measured at 21 °C with a = 0° (number of scans, 3 x 105). Reprinted with permission from Reference 60. Copyright (1997) American Chemical Society... 

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