Deuterium NMR spectra

These absorb at completely different frequencies, and since deuterium and proton chemical shifts are identical (also because deuterium is a spin-1 nucleus), deuterium NMR spectra are hardly ever measured. 

The deuterium NMR spectra of toluene-d0 in aPS solutions consists of two resonances which are resolved and assigned to the methyl and aromatic groups. In these solutions spin-spin or dipolar couplings are small and consequently are not observed. As the temperature is lowered, the aromatic resonance systematically broadens while the methyl resonance remains relatively constant in width. The linewidths of the aromatic resonances are the same as those which would be predicted from the T2 measurements reported below. The separated resonances make it possible to determine the relaxation times of each type of resonance. 

Fig. 10a. Deuterium NMR spectra of PHBA/PHNA 52/48 at the temperatures indicated, b I3CNMR spectra of PHBA (I3C)/PHNA 30/70 at the temperatures indicated...

Oth Mullen Gilles Schroder Helv. Chim. Acta 1974, 57,1415 Nakanishi Yamamoto Tetrahedron Lett. 15174, 1803 Gunther Ulmen Tetrahedron 1974, 30, 3781. For deuterium nmr spectra see Poupko Zimmermann Luz J. Am. Chem. Soc. 1904, 106, 5391. For a crystal structure study, see Luger Buschmann McMullan Ruble Matias Jeffrey J. Am. Chem. Soc. 19 6,108. 7825. 

E5-2 When 13C-labelled formaldehyde, 13CH20, is fed to live cultures of bacteria in an NMR spectrometer, the metabolism of the label can be followed by 13C NMR. Many bacterial species produce roughly equal amounts of formate (HCOO ) and methanol (CH3OH). This is reminiscent of the purely chemical Cannizzaro reaction in which a hydride ion (H ) is transferred directly from one formaldehyde molecule to another. The accompanying 61 MHz deuterium NMR spectra are of methanol that results from the metabolism of deuterium-labelled formaldehyde, CD2O, by Escherichia coli and Pseudomonas putida. What do they tell us about possible Cannizzarase enzymes in those organisms ... 

Figure 2. Deuterium NMR spectra of n-hexadecane-dg solubilized in a lamellar dispersion of C12E4/H2O as a function of oil content (the numbers are weight fraction of oil) at a fixed soap.water ratio (60 40 W/W).

Figure 7. Solid state deuterium NMR spectra of labelled poly(butylene terephthalate). Calculated spectra are for a two-site hopping model between two orientations of the C-D bond differing by 103° (Jelinski, L. W. Dumais, J. J. Engel, A. K. Macromolecules, 1983, 1 6, 492).

The samples for NMR spectroscopy were melted into glass tubes and allowed to cool from the melt. The observed deuterium NMR spectra are reproducible with temperature cycling, thus providing evidence that the thermal history induced by acquiring temperature-dependent spectra of the samples does not greatly affect the properties that we are measuring. 

Inversion-recovery deuterium NMR spectra were obtained by performing a 180°-r-90° pulse sequence, followed by the quadrupolar echo sequence (12). Spin lattice relaxation times were estimated from the null points in the inversion-recovery spectra. 

Figure 4. Solid state deuterium NMR spectra of (a) poly (butylene terephthalate) (b) segmented co-polyester containing 0.96 mole fraction of poly (butylene terephthalate) hard segments and (c) segmented copolymer containing 0.87 mole fraction hard segments. (See text for specific deuterium labeling patterns.) All spectra were obtained with the quadrupole echo pulse sequence at 20 °C and 55.26 MHz, using 30 ts at the tj quadrupole echo delay time.

It is of interest to estimate the amount of hard segment which gives the sharp line, and further, to determine if the poly (butylene terephthalate)-like broad line represents deuterons which undergo motions which are identical to those observed in the poly(butylene terephthalate) homopolymer. These points are addressed for the copolymer containing 0.87 mole fraction hard segments, by the solid state deuterium NMR spectra shown in Figure 6. 

Figure 6. Experimental (a), calculated (b), and difference (c) solid state deuterium NMR spectra for the segmented copolymer with 0.87 mole fraction of hard segments. The spectrum in (a) was obtained at 55.26 MHz and 20 C, using the quadrupole echo pulse sequence. The dashed line in (b) represents the sum calculated for the broad and narrow components in a respective 10 1 ratio. (See text for details of the calculation.) The spectrum in (c) is the difference spectrum obtained by subtracting the spectrum of poly(butylene terephthalate) (Figure 4a) from the segmented copolymer spectrum (Figure 6a).

Predict the proton and deuterium NMR spectra of D-CH2-O-CH3, remembering that the spin quantum number for deuterium = 1. Compare the proton spectrum to that of F-CH2-O-CH3 (Problem 22a). 

Abe, A., and Furuya, H., Orientational characteristics of main-chain polymer liquid crystals as revealed by the rotational isomeric state analysis of deuterium NMR spectra, Macro-molecules, 22, 2982-2987. (1989). 

Figure 19. Calculated deuterium NMR spectra for the aramatic deuterons in p-xylene under different conditions (a) rigid ring (b) ring executing 180 jumps about the para axis (c) ring rotating freely about the para axis (28).

Figure 7. Temperature dependence of deuterium NMR spectra of DPPH-(ortho d4).

In nematic solvents, alkanes are found to acquiesce and conform to the nematic constraints, while retaining considerable freedom. The deuterium NMR spectra of perdeuteriated alkanes were simulated quantitatively and complete agreement was found between a motional model and the experiment . ... 

Since their discovery in 1949 , n-alkane urea inclusion compounds (UIC) have fascinated chemists and spectroscopists alike . However, there is disagreement about the interpretation of the deuterium NMR spectra of UICs. Originally, it was believed that in these channel clathrates the alkanes exist in an a -trans conformation. Recently, it was shown that significant amounts ca 30%) near the end of the chains are present in a gauche conformation. An illustration of the possible alkane conformations based upon MM2 calculations is shown in Figure 4 . 

The deuterium NMR spectra of perdeuteriated n-hexane in zeolites " " indicate that the hexane molecule reptates within the zeolite and imply a significant interaction between the hydrocarbon and the zeolite cage wall. For cyclohexane the data suggest " that the chair to chair interconversion rate is damped by the zeolite. 

Solid-echo deuterium NMR spectra provided unique evidence about motions occurring in the crystals at those extreme conditions. Among other methods reported in the literature, only Raman spectroscopy could identify... 

Fig. 2 Static deuterium NMR spectra at 4900 bar of polyethylene (a) in the hexagonal phase and (b) in the orthorhombic phase, showing the mobility of the hexagonal phase, as indicated by the shrinkage of the singularities to about 50 kHz. The isotropic signal at the center of the spectrum represents the mobile amorphous phase...

Fig. 9. 23 depicts the deuterium NMR spectra of di-myristoylphosphatidylcholine labelled at the terminal methyl group (spectra (A)-(B)) or at position 6 (spectra (E)-(H)) of the 2-chain (Rice et al., 1979). Spectra (A) and (E) show the pure lipid spectra in the liquid-crystalline state, whereas spectra (D) and (H) correspond to the respective samples in the gel state (Tc = 23 °C). An increase in the order parameter upon cooling is apparent. The effect of cholesterol, at a concentration of 50 mol %, is seen in spectra (B), (C), (F) and (G). It is clear that cholesterol induces an... 

With the aim of quantitatively predicting the orientational order of rigid solutes of small dimensions dissolved in the nematic liquid crystal solvent, 4-n-pentyl-4 cyanobiphenyl (5CB), an atomistic molecular dynamics (MD) computer simulation has been applied. It is found that for the cases examined the alignment mechanism is dominated by steric and van der Waals dispersive forces. A computer simulation of the deuterium NMR spectra of molecules in a thin nematic cell has been carried out and the director distribution in the cell has been studied. An experiment for the direct estimation of an element of the order matrix from H NMR spectra of strongly dipolar coupled spins that is based on the multiple quantum spin state selected detection of single quantum transitions has been proposed. The experiment also enables obtaining nearly accurate starting dipolar... 

Abstract Monte Carlo simulations of lattice spin models are a powerful method for the investigation of confined nematic liquid crystals and allow for a study of the molecular organization and thermod3mamics of these systems. Investigations of models of polymer-dispersed liquid cr3rstals are reviewed devoting particular attention to the calculation of deuterium NMR spectra from the simulation data. 

Deuterium NMR spectra at different temperature ranging from — 75 to - -10°C were obtained from fully H20-hydrated POPC (l-palmitoyl-2-oleoylphosphatidylcholine) multilamellar vesicles (MLVs), prepared with and without cholesterol, to determine the freezing temperature of water and the effect of cholesterol on the freezing temperature of water in POPC bilayers. P NMR data suggest that lipid bilayers can be aligned at low temperatures, while N NMR experiments demonstrate that such aligned samples can be used to enhance the signal-to-noise ratio of N chem. shift spectra of a 37-residue human antimicrobial peptide, LL-37. ... 

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