Molecular interactions induction

Knowles P J and Meath W J 1986 Non-expanded dispersion and induction energies, and damping functions, for molecular interactions with application to HP.. . He Mol. Phys. 59 965... 

Absorption, metaboHsm, and biological activities of organic compounds are influenced by molecular interactions with asymmetric biomolecules. These interactions, which involve hydrophobic, electrostatic, inductive, dipole—dipole, hydrogen bonding, van der Waals forces, steric hindrance, and inclusion complex formation give rise to enantioselective differentiation (1,2). Within a series of similar stmctures, substantial differences in biological effects, molecular mechanism of action, distribution, or metaboHc events may be observed. Eor example, (R)-carvone [6485-40-1] (1) has the odor of spearrnint whereas (5)-carvone [2244-16-8] (2) has the odor of caraway (3,4). 

The selection of the solvent is based on the retention mechanism. The retention of analytes on stationary phase material is based on the physicochemical interactions. The molecular interactions in thin-layer chromatography have been extensively discussed, and are related to the solubility of solutes in the solvent. The solubility is explained as the sum of the London dispersion (van der Waals force for non-polar molecules), repulsion, Coulombic forces (compounds form a complex by ion-ion interaction, e.g. ionic crystals dissolve in solvents with a strong conductivity), dipole-dipole interactions, inductive effects, charge-transfer interactions, covalent bonding, hydrogen bonding, and ion-dipole interactions. The steric effect should be included in the above interactions in liquid chromatographic separation. 

At this pressure, the polarizability/volume of SF CO2 is a little less than that of n-hexane, which suggests that there are other molecular interactions between CO2 and phenol blue in addition to dispersion and induction. The likely possibilities include electron donor-acceptor forces and dipole-quadrupole interactions. 

The induction of chirality in liquid crystals (LCs) has a long history [100-104]. The supramolecular induction can be used to assign absolute configurations [105-108], conformations of molecules [109,110] and the interplay between inter- and intra-molecular interactions [111], and models can be developed to justify the sense of the inductions that are observed. Twisting powers of dopants—the twist per mole—can be pushed to extraordinary values [112]. Given the history and vast body of work, we will focus here on the more contemporary aspects of work in this area. 

In non-dipolar dielectrics sufiSciently dense for molecular interaction, the temperature-dependent polarization (241) is generally non-zero. Such interaction will lead to an effect consisting in the induction, in any given molecule immersed in the dense medium, of a dipole moment M by the fluctuating electric field of the permanent quadrupoles, > octu-poles, >hexadecapoles, and in general multipoles" of its nei bours. 

Equation (62) can be used to compare the relative magnitudes of ionic, dipolar, and induction contributions to a molecular interaction, and a ratio of 800 3 1 was calculated, respectively, when qx = 1 e, = fi2 = 1D, a, = a2 = (47t 0)3 x 10 30m3, and a molecular separation distance of r = 0.5 nm at T = 300 K, were selected for an indicative example. This shows the importance of the presence of an ion in a medium. Equation (62) also shows the molecular volume effect such that the efficiency of a dipolar interaction depends on (fd2lr6 (fd/V)2). rather than the absolute value of the dipole moment. 

Surface tension of polymers can be divided into two components—polar (yP) and dispersion (y )— to account for the type of attraction forces at the interfaces. The chemical constitution of the surface determines the relative contribution of each component to the surface tension. The polar component is composed of various polar molecular interactions including hydrogen bonding, dipole energy, and induction energy, while the dispersion component arises from London dispersion attractions. The attractive forces (van der Waals and London dispersion) are additive, which results in the surface tension components to be additive y = y + y. ... 

A useful alternative approach is to isolate the components of the perturbation expansion, namely the repulsion, electrostatic interaction, induction, and dispersion terms, and to calculate each of them independently by the most appropriate technique. Thus the electrostatic interaction can be calculated accurately from distributed multipole descriptions of the individual molecules, while the induction and dispersion contributions may be derived from molecular polarizabilities. This approach has the advantage that the properties of the monomers have to be calculated only once, after which the interactions may be evaluated easily and efficiently at as many dimer geometries as required. The repulsion is not so amenable, but it can be fitted by suitable analytic functions much more satisfactorily than the complete potential. The result is a model of the intermolecular potential that is capable of describing properties to a high level of accuracy. 

The expression (18) represents the induction effect of the earlier theory. If we add it to the expression estimated in (13), then we obtain the for the temperature-dependent portion of the molecular interaction... 

DPT calculations are not suitable for evaluating the inter molecular interactions of aromatic molecules, as dispersion is the major source of the attraction in the interactions of aromatic molecules, with the exception of cation/TT interactions. DPT calculations using basis sets with polarization functions provide sufficiently accurate intermolecular interaction energies for the cation/TT interactions, as DPT calculations can reproduce electrostatic and induction energies sufficiently accurately. 

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