A study of kinetic isotope effects, theoretical calculations, and dynamic trajectories of the C(2)-C(6) (Schmittel)/ene cyclization of enyne-allenes has been reported.178 For (74), the isotope effect l=h/ l=d = 1-43 is consistent with a highly asynchronous [Pg.489]

In order to carry out a priori theoretical calculations of the potential energy for systems with a large number of electrons, the semitheoretical methods use effective potentials which simulate the core electrons.19 48 Note here that the inclusion of relativistic effects may be important in the description of the effective potentials in heavy atoms.49 [Pg.270]

We present a detailed theoretical calculation, with experimental verification, of the nonlocal molecular reorientation of the nematic-liquid-crystal director axis induced by a cw Gaussian laser beam. The natures of the torque balance equations and the solutions are significantly different for normally and nonnormally incident laser beams. The nonlocal effects resulting from molecular correlation effects are particularly important for laser spot sizes that are different (smaller or larger) from the sample thickness. Experimental measurements for the transverse dependence of the molecules and the dependence of the Freedericksz threshold as a function of the laser beam sizes are in excellent agreement with theoretical results. We also comment on the effect of these nonlocal effects on transverse optical bistability. [Pg.136]

A new study has been reported of the hydrolysis of the p-tolyldiazonium cation using a combination of carbon kinetic isotope effects, theoretical calculations, and dynamics trajectories. Overall, the results are in best accord with a process at the boundary between. S N 1 and. S N2Ar mechanisms.1 There has been a kinetic study of the thermolysis of o-carboxybenzenediazonium fluoride to give o-fluorobenzoic acid in liquid hydrogen fluoride under pressure.2 [Pg.155]

We use here the Ericksen-Leslie continuum theory to describe the effect. The rotational motion of the director (i.e., molecular reorientation) is driven by the pump laser pulse, but it is also coupled with the translation motion (flow) of the fluid through viscosity. Thus, with a finite pump beam, a rigorous theoretical calculation would require the solution of a set of coupled three-dimensional nonlinear partial differential equations for the angle of [Pg.191]

These results are consistent with an Ad 2 (addition-electrophilic-bimolecular) mechanism for a first step of protonation, followed by a glycosyl transfer usually directed by the kinetic anomeric effect. Theoretical calculations [13] have shown [Pg.369]

This expression has a formal character and has to be complemented with a prescription for its evaluation. A priori, we can vary the values of the fields independently at each point in space and then we deal with uncountably many degrees of freedom in the system, in contrast with the usual statistical thermodynamics as seen above. Another difference with the standard statistical mechanics is that the effective Hamiltonian has to be created from the basic phenomena that we want to investigate. However, a description in terms of fields seems quite natural since the average of fields gives us the actual distributions of particles at the interface, which are precisely the quantities that we want to calculate. In a field-theoretical approach we are closer to the problem under consideration than in the standard approach and then we may expect that a simple Hamiltonian is sufficient to retain the main features of the charged interface. A priori, we have no insurance that it [Pg.806]

The scaled particle model (SPM) was the first essentially molecular theory of hydrophobicities (see Scaled Particle Theory), It derived from an earlier scaled particle theory, a successful theoretical calculation of the thermodynamic properties of the hard sphere liquid. Pierotti then adapted the scaled particle theory to produce a solubility model for realistic liquids by a natural replacement of the hard sphere pressure with the measured pressure of the real solvent of interest. With attractive solute-solvent interactions treated perturba-tively this scaled particle model was remarkably successful. The SPM is the molecular theory of hydrophobicities most widely considered among biomolecular modelers. However, its success is somewhat fortuitous.For example, though the SPM predicts a reasonable value for the surface tension for the water liquid-vapor interface at room temperature, the predicted temperature dependence is wrong. Since entropies and temperature dependencies are special goals of theories of hydrophobic effects, this incorrect temperature dependence is important. [Pg.1292]

The second and most important point of Table 3.16 is that the correct Hartree-Fock results are in qualitative disagreement with experiment. In the molecular orbital Hartree-Fock model, the l7r orbital is the highest occupied orbital, yet the lowest experimental ionization potential corresponds to the production of an ion with symmetry. This implies a breakdown of the simple orbital picture of ionization. The Hartree-Fock picture is an approximation. For the case of N2 this approximation is not sufficiently accurate for even a qualitative understanding of the ionization phenomena. As we shall see in Chapters 4 and 7, when the single determinant Hartree-Fock model is replaced by a multideterminantal model, with its associated inclusion of correlation effects, theoretical calculations and experiment ultimately agree on the ionization spectra of N2. [Pg.197]

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