Dipole-polarization forces

Polar interactions arise from electrical forces between localized charges such as permanent or induced dipoles. Polar forces are always accompanied by dispersive interactions and may also be combined with ionic interac-... 

FIGURE 4 3 Adipole-dipole attractive force Two molecules of a polar sub stance associate so that the positively polarized region of one and the negatively polarized region of the other attract each other... 

Induced dipole/induced dipole forces are the only intermolecular attractive forces available to nonpolar molecules such as alkanes In addition to these forces polar molecules engage m dipole-dipole and dipole/mduced dipole attractions The dipole-dipole attractive force is easiest to visualize and is illustrated m Figure 4 3 Two molecules of a polar substance experience a mutual attraction between the positively polarized region of one molecule and the negatively polarized region of the other As its name implies the dipole/induced dipole force combines features of both the induced dipole/mduced dipole and dipole-dipole attractive forces A polar region of one mole cule alters the electron distribution m a nonpolar region of another m a direction that produces an attractive force between them... 

Both polar compounds ethanol and fluoroethane have higher boiling points than the nonpolar propane We attribute this to a combination of dipole/mduced dipole and dipole-dipole attractive forces that are present m the liquid states of ethanol and fluo roethane but absent m propane... 

In general aldehydes and ketones have higher boiling points than alkenes because they are more polar and the dipole-dipole attractive forces between molecules are stronger But they have lower boiling points than alcohols because unlike alcohols two carbonyl groups can t form hydrogen bonds to each other... 

Two Molecules Interacting and Held Together by Dispersive Forces and Polar Forces from Permanent Dipoles... 

Polar molecules attract other polar molecules through dipole-dipole intermolecular forces. Polar solutes tend to have higher solubilities in polar solvents than in nonpolar solvents. Which of the following pairs of compounds would be expected to have the higher solubility in hexafluorobenzene, Cf,I... 

The main difference between a molecule-molecule (M-M) collision and an ion-molecule (M+-M) collision is the presence of a polarization force in the latter system owing to the attraction between the static charge on M+ and the dipole moment induced on M. For a large inter molecular separation, the polarization energy is known as... 

Polar forces also arise from electrical charges on the molecule but in this case from permanent or induced dipoles. It must be emphasized... 

The basic principles are described in many textbooks [24, 26]. They are thus only sketchily presented here. In a conventional classical molecular dynamics calculation, a system of particles is placed within a cell of fixed volume, most frequently cubic in size. A set of velocities is also assigned, usually drawn from a Maxwell-Boltzmann distribution appropriate to the temperature of interest and selected in a way so as to make the net linear momentum zero. The subsequent trajectories of the particles are then calculated using the Newton equations of motion. Employing the finite difference method, this set of differential equations is transformed into a set of algebraic equations, which are solved by computer. The particles are assumed to interact through some prescribed force law. The dispersion, dipole-dipole, and polarization forces are typically included whenever possible, they are taken from the literature. 

The ion-dipole intermolecular force is different in that two different species must be present an ion from one species and a polar molecule from a different species. 

Although the behavior of the base perfume, and thus the odor value (OV) of each component, can be known, the OV in the new mixture will change because the OV depends largely on the solvent and the remaining aromatic components present in the perfume mixture. This is due to molecular size and in great extent to physical interactions at the molecular level, such as polarity forces (i.e. ion-dipole, dipole-dipole, hydrogen bonding forces, and others), in other words to the structure. 

Ion-dipole intermolecular forces occur between ions and polar molecules. 

Many different types of forces arise from molecule-molecule interaction. They may be electrostatic forces between permanent dipoles, induction forces between a permanent dipole and induced dipoles, or dispersion forces between non-polar molecules, etc. (Prausnitz, U2)). Forces involved in molecule-molecule interaction are known to be short-range in nature. 

While the solubility parameter can be used to conduct solubility studies, it is more informative, in dealing with charged polymers such as SPSF, to employ the three dimensional solubility parameter (A7,A8). The solubility parameter of a liquid is related to the total cohesive energy (E) by the equation 6 = (E/V) 2, where V is the molar volume. The total cohesive energy can be broken down into three additive components E = E j + Ep + Ejj, where the three components represent the contributions to E due to dispersion or London forces, permanent dipole-dipole or polar forces, and hydrogen bonding forces, respectively. This relationship is used... 

As the temperature of a gas system is lowered, the speed of the molecules decreases. When these lower-speed molecules collide with one another, attractive forces between the molecules become more significant, and a temperature will be reached where condensation occurs - the vapor state converts to liquid. Di-pole-dipole attractive forces are most important in causing condensation, and molecules with substantial partial charges, resulting from polar covalent bonds, t3q3ically have high condensation temperatures. (Condensation temperature will be the same as the boiling point of a liquid, approached from the opposite direction. )... 

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