Interactions between molecules induction

The interaction between molecules A and B is now energetically favorable as a result of the dipole moment induced in B. The susceptibility of B to this type of induction depends on... 

For tliis class of mixtures, interactions between molecules of like species are different in kind for the two species. In particular, two molecules of the polar species experience a direct-electrostatic interaction and a (usually weak) induction interaction, in addition to the usual dispersion interaction here, the attractive forces are stronger than would be observed for a nonpolar species of similar size and geometry. Interactionbetween uiihke species, on the other liand, involves only the dispersion and (weak) induction forces. One therefore expects to be positive, only more so than for otlierwise similar NPNP mixtures. Experiment bears tliis out, on average (Fig. 16.5). 

The interaction between molecules that do not form chemical bonds arises from electrostatic, induction and dispersion effects. The energy of interaction... 

For van der Waals interactions between molecules in a gas phase, the orientation interaction can yield from 0% (nonpolar molecules) up to 70% (molecules of large permanent dipole moment, like H2O) of the value of the contribution of the induction interaction in oi j is usually low, about 5 to 10% the contribution of the dispersion interaction might be between 24% (water) and 100% (nonpolar hydrocarbons) for numerical data, see Reference 34. 

There are many other examples of the dramatic effects that small groups and their positions along the main chain of an MLC can have on phase behavior. Demonstrations of both induction and destruction of liquid crystallinity have been documented when even small groups like methyl are added [148-150] they can affect packing arrangements by influencing conformations of single molecules and electrostatic interactions between molecules. Unfortunately, the manifestations of these perturbations on MLCs and PLCs are not easily related in many cases. 

The van der Waals forces represent an averaged dipole-dipole interaction, which is a superposition of three contributions (1) orientation interaction, interaction between two permanent dipoles [285] (2) induction interaction interaction between one permanent dipole and one induced dipole [286] (3) dispersion interaction interaction between two induced dipoles [287]. The energy of van der Waals interaction between molecules i and j obeys the law [288]... 

In a similar way, the dissolution of an ionic substance in a nonpolar solvent will also occur with an induction of dipoles in the solvent molecules by the solute ions. The equation makes reference to the interactions between two molecules. Because the polarization energy (of solute or solvent) is not of pairwise additive magnitude, the consideration of a third molecule should be carried out simultaneously, since it impossible to decompose the interaction of the three bodies in a sum of the interactions of two bodies. The interactions between molecules in solution are different from those which take place between isolated molecules. For this reason, the dipolar moment of a molecule may differ considerably between the gas phase and the solution, and it will depend in a complicated fashion on the interactions which may take place between the molecule of solute and its specific surroundings by solvent molecules. 

There are tliree important varieties of long-range forces electrostatic, induction and dispersion. Electrostatic forces are due to classical Coulombic interactions between the static charge distributions of the two molecules. They are strictly pairwise additive, highly anisotropic, and can be either repulsive or attractive. 

Consider the interaction of a neutral, dipolar molecule A with a neutral, S-state atom B. There are no electrostatic interactions because all the miiltipole moments of the atom are zero. However, the electric field of A distorts the charge distribution of B and induces miiltipole moments in B. The leading induction tenn is the interaction between the pennanent dipole moment of A and the dipole moment induced in B. The latter can be expressed in tenns of the polarizability of B, see equation (Al.S.g). and the dipole-mduced-dipole interaction is given by... 

Note the r dependence of these tenns the charge-indiiced-dipole interaction varies as r, the dipole-indiiced-dipole as and the quadnipole-mduced-dipole as In general, the interaction between a pennanent 2 -pole moment and an induced I -pole moment varies as + L + l) gQ enough r, only the leading tenn is important, with higher tenns increasing in importance as r decreases. The induction forces are clearly nonadditive because a third molecule will induce another set of miiltipole moments in tlie first two, and these will then interact. Induction forces are almost never dominant since dispersion is usually more important. 

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