Induced dipole forces

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... 

Van der Waals forces (Section 2 17) Intermolecular forces that do not involve ions (dipole-dipole dipole/mduced dipole and induced dipole/induced dipole forces)... 

Neither bromine nor ethylene is a polar molecule, but both are polarizable, and an induced-dipole/induced-dipole force causes them to be mutually attracted to each other. This induced-dipole/induced-dipole attraction sets the stage for Br2 to act as an electrophile. Electrons flow from the tt system of ethylene to Bi, causing the weak bromine-bromine bond to break. By analogy to the customary mechanisms for electrophilic addition, we might represent this as the formation of a car bocation in a birnolecular- elementary step. 

Click Chemistry Interactive for the self-study module dipole-induced dipole forces. 

For ion-molecule reactions where the interaction can be attributed to ion-induced dipole forces it has been shown (11) that the rate constant should be independent of ion energy—i.e., the thermal and 10.5 volt cm.-1 rate constants should be the same. The third column in Table II shows that for most of the reactions studied the ratio k (thermal)/ (10.5 volts/ cm.) is in the range 0.7-1.1. Considering the errors involved this is not significantly different from unity, indicating that most of the reactions... 

Induced-dipole/induced-dipole forces, also called temporary dipoleAemporary dipole forces, are weak attractive forces that exist between all molecules. They arise when an instantaneous imbalance in the electron distribution in a molecule induces a corresponding imbalance in neighbouring molecules, leading to a weak electrostatic attraction. 

Induced-dipole/induced-dipole forces increase in strength as the number of electrons in the molecule increases. This phenomenon is illustrated by the increase in boiling temperatures of the halogens down group 7. 

Permanent-dipole/permanent-dipole forces are weak attractive forces between permanently polar molecules. S+ atoms in one molecule attract S atoms in another molecule. They act in addition to the induced-dipole/induced-dipole forces. 

Dipole-induced dipole forces. A molecule with a strong molecular or bond dipole can induce a dipole in a molecule nearby that is polarizable. These Keesom forces have the same inverse 6th power dependence with distance. An example could be the interaction of chlorobenzene with naphthalene. 

For each of the substances the possible answers are ionic bonding, covalent bonding, metallic bonding, hydrogen bonding, dipole-dipole force, or London force. Forces, such as ion-dipole forces and ion-induced dipole forces, are not choices because these require the presence of two or more substances. For example, sodium chloride cannot utilize either of these two forces, but sodium chloride in water can. (Sodium chloride in water exhibits ion-dipole forces.)... 

Induction of electric charge occurs when a charge on one object causes a change in the distribution of charge on a nearby object. Rubbing a balloon to make it "stick" to a wall is an example of charging by induction. There are two types of charge-induced dipole forces. 

An ion-induced dipole force results when an ion in close proximity to a non-polar molecule distorts the electron density of the non-polar molecule. The molecule then becomes momentarily polarized, and the two species are attracted to each other. This force is active during every moment of your life, in the bonding between non-polar O2 molecules and the Fe " ion in hemoglobin. Ion-induced dipole forces, therefore, are part of the process that transports vital oxygen throughout your body. 

A dipole-induced dipole force is similar to that of an ion-induced dipole force. In this case, however, the charge on a polar molecule is responsible for inducing the charge on the non-polar molecule. Non-polar gases such as oxygen and nitrogen dissolve, sparingly, in water because of dipole-induced dipole forces. 

In any of its different modes, LC behaves as a dynamic adsorption process. Analyte molecules, while moving through the porous packing bead, tend to interact with the surface adsorption sites. Depending on the LC mode, different types of adsorption forces may be included in the retention process. Hydrophobic (nonspecific) interactions are the main ones in reversed-phase separations. Polar interactions including dipole-dipole, and dipole-induced dipole forces dominate in the normal-phase mode, whereas ionic interactions are responsible for the retention... 

Figure 3.1 Illustration of the various molecular interactions arising from uneven electron distributions (a) dispersive forces, (b) dipole-induced dipole forces, (c) dipole-dipole forces, (d) electron acceptor-electron donor forces.

The greater the surface area the greater the number of induced dipole-induced dipole forces of attraction that can occur between the gecko s foot and the surface, such as the underside of a leaf or a wall or ceiling. 

The insolubility of ionic compounds in nonpolar solvents is a similar phenomenon. The solvation energies are limited to those from ion-induced dipole forces, which are considerably weaker than ion-dipole forces and not large enough to overcome the very strong ion-ion forces of the lattice. 

Even in atoms in molecules which have no permanent dipole, instantaneous dipoles will arise as a result of momentary imbalances in electron distribution. Consider the helium atom, for example. It is extremely improbable that the two electrons in the Is orbital of helium will be diametrically opposite each other at all times. Hence there will be instantaneous dipoles capable of inducing dipoles in adjacent atoms or molecules. AnothCT way of looking at this phenomenon is to consider the electrons in two or more "nonpolar" molecules as synchronizing their movements (at least partially) to minimize electron-electron repulsion and maximize electron-nucleus attraction. Such attractions are extremely short ranged and weak, as are dipole-induced dipole forces. The energy of such interactions may be expressed as... 

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