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Pseudo-isotropic

Figures 12a and 12b illustrate the ESR spectra at —180°C and 25°C, respectively, of Nb(7r-allyl)4 after reaction with Manosil VN3 previously dried at 200°C. Figure 12b is complex and shows a mixture of at least two species present in the system. The major peaks are present in the system. The major peaks are also present in the frozen solution spectrum (Figure 10a) indicating that they arise from a rigidly held surface species. This species arises from the reaction of Nb(7r-allyl)4 with two adjacent hydroxyl groups and is therefore the double oxide bridge configuration (Reaction 3). Upon further addition of Nb(7r-allyl)4 to the silica, the pseudo isotropic spectrum (Figure lib) becomes more evident. This suggests that Nb(7r-allyl)4 reacts preferentially with the paired hydroxyl groups, an observation in accord with the literature (63). Figures 12a and 12b illustrate the ESR spectra at —180°C and 25°C, respectively, of Nb(7r-allyl)4 after reaction with Manosil VN3 previously dried at 200°C. Figure 12b is complex and shows a mixture of at least two species present in the system. The major peaks are present in the system. The major peaks are also present in the frozen solution spectrum (Figure 10a) indicating that they arise from a rigidly held surface species. This species arises from the reaction of Nb(7r-allyl)4 with two adjacent hydroxyl groups and is therefore the double oxide bridge configuration (Reaction 3). Upon further addition of Nb(7r-allyl)4 to the silica, the pseudo isotropic spectrum (Figure lib) becomes more evident. This suggests that Nb(7r-allyl)4 reacts preferentially with the paired hydroxyl groups, an observation in accord with the literature (63).
Other models, for instance with the angle 3 weighted according to an appropriate scheme, might be equally satisfactory. However, one of the main conclusions remains that the molecular motion of non-spherical guests in non-spherical cages cannot be regarded as isotropic, or even pseudo-isotropic. [Pg.246]

Fig. 17 NMR lineshapes of Cd(CN)2.2QDj2 as a function of temperature, indicating reorientation of the cyclohexane about the molecular 3-fold axis at 77K and rapid pseudo-isotropic motion by 148K [49]. Contrast these lineshapes with those shown in Figure 15. Fig. 17 NMR lineshapes of Cd(CN)2.2QDj2 as a function of temperature, indicating reorientation of the cyclohexane about the molecular 3-fold axis at 77K and rapid pseudo-isotropic motion by 148K [49]. Contrast these lineshapes with those shown in Figure 15.
For those liquid crystals having dielectric anisotropies As > 0, an applied field of the order of a few volts d.c. over a film thickness of 23/im led to homeotropic alignment as schematically indicated in Fig. 2(b), i.e. a Freedericksz transition. In all cases the thickness of the cell was maintained with Mylar spacers. The long carbazole axis was also found to lie perpendicular to the nematic director in the case of homeotropic alignment above the critical field, since the order parameter approached zero and the system appeared to be pseudo-isotropic. All absorption measurements are made normal to the plane of the quartz plates. For K-0327 for which As < 0, and < 2) parallel alignment, there is no change in order... [Pg.316]

Figure 9. Charge and discharge characteristics of (a) MCMB700 (itegion Q hi 1M UCKVEC + DEC (l l by volume). From reference 16 reproduced by permission of The Bectrochemical Society, Inc and (b) petroleum-pitdvbased pseudo-isotropic caitxxi (nc. Region D) in l M UCKVEC-t-cftriettioxyediane (DME) (1 1 by volume) [data from 29]. Figure 9. Charge and discharge characteristics of (a) MCMB700 (itegion Q hi 1M UCKVEC + DEC (l l by volume). From reference 16 reproduced by permission of The Bectrochemical Society, Inc and (b) petroleum-pitdvbased pseudo-isotropic caitxxi (nc. Region D) in l M UCKVEC-t-cftriettioxyediane (DME) (1 1 by volume) [data from 29].

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