2H spectra

Fig. 25. Observed and calculated 2H spectra for the crystalline regions of drawn (k m 9) linear polyethylene for various angles of p0 between the draw direction and the magnetic field B0...

Fig. 31. 2H spectra of a polymer model membrane, cf. Fig. 27b), methyl deuterated at the head group. The spectra are compared for the monomer as well as the polymer lamellar phases at the same temperatures, respectively... 

Figure 13 2H spectra of oriented polyethylene. Left, B0 parallel, right, B0 perpendicular to the orientation direction, respectively. Reproduced with permission from Hentschel et al. [74]. Copyright Elsevier 1981. 

Fig. 4. 45-MHz 2H spectra of CD3I on zeolites CsX, HY, and HZSM-5. On CsX the adsorbate forms a framework-bound CD3 group. Methyl iodide is much less reactive on acidic zeolites. It tumbles isotropically in HY and shows restricted motion in HZSM-5. (Courtesy of Larry W. Beck.)...

The potential of other nuclei for the study of surfaces is yet to be explored. Gottlieb and Luz (388) measured 2H spectra of a number of perdeuterated molecules adsorbed on active alumina and interpreted the results in terms of quadrupolar tensors. Yesinowski and Mobley (369) have shown that 19F MAS NMR can provide useful information about fluorinated surfaces of calcium hydroxyapatite, Cas(0H)(P04)3. In particular, l9F, 2H, and H MAS NMR may become powerful techniques for the study of interface systems in general. 

Fig. 39 Experimental and calculated 2H spectra of methyl deuterated BPA-PC at various temperatures and different evolution times, ti (from [35])...

As the 2D 2H spectra are insensitive to the 77--flip motion itself, the observed exchange intensity can only originate from the rotations around the local chain axis. Indeed, the 2D 13C NMR spectrum of 13C carboxyl (Sect. 8.1.4.1) has shown that n-flips of the ester groups are accompanied by rotations around the chain axis by about 20°. 

Hydrides. Hydrogenation of degassed activated vanadium occurs at —20 to — 60 °C and is complete in 8—10 days forming the cubic hydride VH1-93 whose lattice parameter is a = 4.26 A.362 Two quadrupole-split 2H spectra have been observed363 for the interstitial vanadium deuterides VDX 0.2 x 0.9. 

Probing mechanism of the reaction involving intramolecular competition between different isotopic species at several chemically equivalent positions, the number of equivalent sites must be taken into consideration. In the case of deuterium content at natural abundance the concentration of multiply labelled molecule is negligible and not-deuterated molecules are invisible in the 2H NMR. When reaction is taken to the completion the retained and transferred deuterium can be calculated from the 2H spectra of substrate and product. The KIE is given by ... 

Fig. 2. Calculated 2H NMR spectra for the situation illustrated in Fig. 1, where nuclei can move between potential wells and diffuse under the governing potential within wells, (a) 2H MAS spectra, (b) Static 2H spectra. The spectra are calculated as a function of D, the diffusion coefficient and Efi, the potential barrier between wells. Spectra are taken from reference 6.

Figure 15.17 shows 2H spectra of powdered hexamethyl-benzene-D g. Since we are dealing with a powder, we expect powder patterns, and the back-to-back superimposition of a pair of asymmetric powder lineshapes is clearly seen. Quad-rupolar interactions can get quite large, and in most cases they will dominate the chemical shift spectrum. For deuterium, which has a rather tiny quadrupole moment, the quadrupolar interaction varies from about 25 kHz in hexamethylbenzene-D g to about 200 kHz in carboxylate deuterons. In the heavier nuclei, such as 127I, the quadrupolar interaction can reach 2000 MHz No one is ever likely to observe a spectrum that wide. 

F and 2H Spectra.—Substituent effects are reported on the 19F n.m.r. of sterol trifluoroacetates.75 2H N.m.r. has been used to study the state of labelled cholesterol in multibilayers of egg yolk lecithin containing digitonin.76... 

Already in early NMR studies of surfactant adsorption layers, 2H investigations had been the method of choice [27-30], and a number of investigations has evolved in the meantime. The disadvantages over IH studies, i.e. lower sensitivity and the necessity of labelling, are overcompensated by the achievement of quantitative results In the case of no isotropic motional mode averaging the quadnipolar interaction, wide line 2H spectra resulted in order parameters, while for surfactants in the isotropically averaged state linewidths and relaxation rates can be evaluated. 

Fig. 9 2H spectra of single chain (left) and double chain (right) benzene sulfonates on alumina, a) at low coverage, b) at high coverage. Figure adapted from [31], Fig. 2b), 2c) with permission. 

Fig. 10 2H spectra of C12E5, selectively deuterated in the a, P or y position, respectively, and adsorbed to colloidal silica, displayed together with Lorentzian fits, demonstrating a homogeneous line broadening. 

Fig. 12 2H spectra of HDPC-y-d6 on latex particles. The outer two maxima of each spectrum form the Pake pattern, while the central two narrow lines arise from free surfactant and HEX), respectively. The quadrupolar splitting is decreasing from a cationic towards an anionic environment (A to E). Figure taken from [41] with permission. 

Fig. 20 2H spectra of surface adsorbed PMA-dj at 52°C with immobile and mobile components compared to bulk. Figure taken from [69] with permission. 

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