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Contributions of asymmetric

Contribution of Asymmetric and Symmetric CO2 Vibrational Modes into Plasma-Chemical Dissociation Process... [Pg.269]

It has been found (7,9) that Z) > 0, ie, the maximum of an asymmetrical dye, X, is shifted to the short-wavelength region with respect to the arithmetical mean of the parent dye maxima. The phenomenon has been named a deviation (7). The positive deviations in PMDs are explained by the bond order alternation within the polymethine chain caused by different contributions of both end groups to the dye energetic stabiUty (7,9,10). The deviation reaches its maximum at Tqi > 45° and Tqi < 45° if the end groups have > 45° and 4>q2 > 45°, or < 45° and 4>q2 < 45°, then the... [Pg.493]

Vibrational broadening in [162] was taken into account under the conventional assumption that contributions of vibrational dephasing and rotational relaxation to contour width are additive as in Eq. (3.49). This approximation provides the largest error at low densities, when the contour is significantly asymmetric and the perturbation theory does not work. In the frame of impact theory these relaxation processes may be separated more correctly under assumption of their statistical independence. Inclusion of dephasing causes appearance of a factor... [Pg.123]

Considerably less is known about the chemistry of palladium and platinum 1,1-dithio complexes. Of late, there has been only one report that dealt with the synthesis of a large number of palladium dithiocar-bamates 392). Twenty-five yellow palladium dithiocarbamate complexes were obtained by reaction of PdCla with NaR2dtc in methanol solution. Several other reports have appeared in which a few dithiocarbamate complexes of palladium were synthesized. Thus, the novel [Pd (OH)2dtc 2], which is soluble in water, was isolated 393). The synthesis of optically active palladium(II) complexes of AT-alkyl-a-phen-ethyldithiocarbamates, similar to (XXIV), via the reaction between the optically active amine, CS2, and PdCl2, has been described. From ORD and CD spectra, it has been established that the vicinal contribution of a remote, asymmetric carbon center could give rise to optical activity of the d—d transitions of palladium 394). Carbon disulfide has been shown to insert into the Pt-F bond of [PtF(PPh3)3]HF2, and X-ray studies indicated the structure (XXIX). [Pg.261]

The modifier in these cases seems to generate enantioselective sites at the metal surface and helps the molecule to adsorb in a preferred fashion so that the formation of only one stereo- product is possible. There are several milestones that have contributed to this state-of-the-art technology. Discovery of Wilkinson s catalyst led to the feasibility of asymmetric hydrogen transfer with the aid of an optically active Wilkinson-type catalyst for L-DOPA (Monsanto s anti-Parkinson disease drug) synthesis (Eqn. (21)). [Pg.175]

The next major contribution in asymmetric cyclopropanation was the introduction of chiral semicorrin ligands 184 by Fritschi et al.95 This ligand has been used for coordinating with copper and has been found to provide improved enantiocontrol in the cyclopropanation of monosubstituted olefins. Copper(I), coordinated by only one semicorrin ligand, is believed96 to be the catalytically active oxidation state. The copper(I) oxidation state can be reached directly... [Pg.314]

This final chapter summarizes the enzyme-catalyzed asymmetric reactions and introduces some new developments in the area of asymmetric synthesis. Among the new developments, cooperative asymmetric catalysis is an important theme because it is commonly observed in enzymatic reactions. Understanding cooperative asymmetric catalysis not only makes it possible to design more enan-tioselective asymmetric synthesis reactions but also helps us to understand how mother nature contributes to the world. [Pg.501]

We should also be familiar with the meaning of the term conformational asymmetry. We know that different conformations of the same compound have different symmetry and different statistical contribution (i.e., their percentage content is different). Therefore, the total effect on the polarization of light depends on the arrangement of atoms in different conformations and also on the statistical contribution of each conformation. This is called conformational asymmetry. The compound CH3-CH2-CH (CH3)C1 has conformational asymmetry because two identical atoms (c) are situated at the asymmetric centre. This compound has three staggered conformations. [Pg.172]

The dielectric constant is the electrostatic expression of the interaction of atoms and molecules with macroscopic electric fields rather than with the exceedingly strong fields of individual atoms and molecules. The interaction between the homogeneous outside field and electrically asymmetrical (polar) molecules results in a finite effect, since in these molecules the contributions of positive and negative charges do not cancel. [Pg.283]

The successful development of asymmetric cellulose acetate membranes by Loeb and Sourirajan in the early sixties, at the University of California, Los Angeles, has been primarily responsible for the rapid development of Reverse Osmosis (RO) technology for brack sh/sea water desalination. Reverse Osmosis approaches a reversible process when the pressure barely exceeds the osmotic pressure and hence the energy costs are quite low. Theenergy requirement to purify one litre of water by RO is only O.OO3 KW as against 0,7 KV required just to supply the vaporisation energy to change the phase of one litre of water from liquid to vapour by evaporation. Thus RO has an inherent capability to convert brackish water to potable water at economic cost and thus contribute effectively to the health and prosperity of all humanity. [Pg.294]

Several chapters deal with the synthesis of and the synthetic applications of organolithium compounds such as orthometallation, arene catalysed lithiation, addition to carbon-carbon double bonds, their reaction with oxiranes, and asymmetric deprotonation with lithium (-)-sparteine. We gratefully acknowledge the contributions of ah the authors of these chapters. [Pg.1412]


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