Effects of dipole interactions

Principles of Polymer Chemistry. DOI 10.1007/978-l-4614-2212-9 2, 1st and 2nd editions Kluwer Academic/Plenum Publishers 1995, 2000, 

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Rigid model compounds (71NL457 83H817) of the type 146 and 147 were employed to study the effect of dipole interactions between C=0 groups on the conformation of proteins. The lactone C=0 group in 147 confers a marked preferential orientation of the N-acyl group, whereas in 146, two conformers are observed in nearly equal amounts, although the equilibrium is solvent dependent. 

The no-bond function includes the electronic energy of the component molecules, plus terms representing the effect of dipole interactions, dispersion forces, hydrogen bonding and other intermolecular forces. The dative bond functions represent states where an electron has been transferred from the donor molecule to the acceptor, introducing electrostatic interactions and forming a weak covalent link between the resulting radical ions ... 

The results were attributed to the combined effects of dipole interaction and the formation of complexes, but the nature and site of the complexing function were not discussed. Because of the low solubility of the gas, he had to use saturated solutions. But there was no indication of the concentration of HCI in these saturated solutions the jchci values at 25°C are relatively small. 

A most comprehensive discussion of the effect of solvent on spectra has been given by Bayliss and McRae.21 They point out that polarization or dispersion forces are the most general interactions involved in solution and that all solution spectra are subject to a generalized polarization red shift, relative to vapor spectra, due to solvent polarization by the transition dipole. However, these dispersion forces are relatively weak and are easily obscured by the effect of dipole-dipole and dipole-static charge forces in polar, but not highly polarizable, solvents. By applying the Franck-Condon principle, they showed... 

The model of a dipole in a spherical cavity can only provide qualitative insights into the behaviour of real molecules moreover, it cannot explain the effect of electrostatic interactions in the case of apolar molecules. More accurate predictions require a more detailed representation of the molecular charge distribution and of the cavity shape this is enabled by the theoretical and computational tools nowadays available. In the following, the application of these tools to anisotropic liquids will be presented. First, the theoretical background will be briefly recalled, stressing those issues which are peculiar to anisotropic fluids. Since most of the developments for liquid crystals have been worked out in the classical context, explicit reference to classical methods will be made however, translation into the quantum mechanical framework can easily be performed. Then, the main results obtained for nematics will be summarized, with some illustrative... 

A general scheme, based on a rigorous statistical mechanical formulation, for obtaining the interaction between two colloidal particles in a fluid has been outlined. The implementation of the theory is in its early stages. In the DLVO theory and the theory of HLC, it is assumed that the various contributions can be added together. In the MSA, the hard core and electrostatic terms will be additive. However, it is only at low electrolyte concentration that the effect of dipole orientation and the repulsive contribution of the double layer overlap will be additive. There is no reason to believe (or disbelieve) that the van der Waals term should also be additive. 

The effect of dipole-dipole interaction between the Fe3+ heme group of myoglobin and water protons was used to study heme hydration and displacement in the pre-denaturational conformational transition of the molecule (Derzhansci et al. 1970). 

Taylor, J.C., Leigh, J.S. and Cohn, M. (1969) The effect of dipole-dipole interaction between nitroxide radical and a paramagnetic ion on the line shape of the ESR spectra of radical. Proc. Natl. Acad. Sci. USA 64, 219-206. 

With Z-substituted dipolarophiles and phenyl azide, the situation is again delicately balanced and only just dipole-HO-controlled (9.5 eV against 10.7 eV). For the dipole-HO-controlled reaction, we should expect to get adducts oriented as in Fig. 6.36a. However, a phenyl group reduces the coefficient at the neighbouring atom both for the HOMO and for the LUMO, and this will reduce the polarisation of the HOMO. Conversely, it will increase the polarisation for the LUMO and hence increase the effectiveness of the interaction of the LUMO of the dipole with the HOMO of the dipolarophile, as in Fig. 6.36b. The difference in... 

The structures of the pairs have been determined by ab initio calculations. Surprisingly, while the absorption spectrum of the solvated electron presents a single band located around 2250 nm, the absorption spectra of the pairs are blue-shifted and composed of two bands (Fig. 7)7 Those spectra were interpreted as a perturbation of the solvated electron spectrum with the use of an asymptotic model. This model describes the solvated electron as a single electron trapped in a THF solvent cavity and takes into account the effects of electrostatic interaction and polarization due to the solutes that are modeled by their charge distribution. It was shown that the p-like excited states of the solvated electron can be split in the presence of molecules presenting a dipole. So, the model accounts for the results obtained with dissociated alkali and non-dissociated alkaline earth salts in THF since ionic solutes yield absorption spectra with only one absorption band, and dipolar neutral solutes yield absorption spectra with two bands (Fig. 8). ... 

Two explanations have been advanced to account for the anomeric effect. The first involves the stabilizing effect of bonding interactions between n electrons on one oxygen atom and the a orbital of the bond connecting the other oxygen atom and the central anomeric carbon atom [58]. The second involves destabilizing dipole-dipole repulsion between the two oxygen atoms and their lone pairs [54]. The relative importance of these factors has been difficult to establish. 

Burshtein, K. Y., Serebryakov, E. P. The regioselectivity of a,P-enone photoanneiation with monosubstituted acetylenes a possible effect of dipole-dipole interactions. Tetrahedron 1978, 34, 3233-3238. 

Solid-state NMR spectra of dilute nuclei in organic molecules are broadened by chemical-shift anisotropy and dipole-dipole couplings between H and C [Vanl]. The effect of these interactions can be eliminated from the NMR spectrum by MAS in combination... 

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