Dipole induced bonding

The raie gas atoms reveal through their deviation from ideal gas behavior that electrostatics alone cannot account for all non-bonded interactions, because all multipole moments are zero. Therefore, no dipole-dipole or dipole-induced dipole interactions are possible. Van der Waals first described the forces that give rise to such deviations from the expected behavior. This type of interaction between two atoms can be formulated by a Lennaid-Jones [12-6] function Eq. (27)). 

Nonbonded interactions are the forces be tween atoms that aren t bonded to one another they may be either attractive or repulsive It often happens that the shape of a molecule may cause two atoms to be close in space even though they are sep arated from each other by many bonds Induced dipole/induced dipole interactions make van der Waals forces in alkanes weakly attractive at most distances but when two atoms are closer to each other than the sum of their van der Waals radii nuclear-nuclear and electron-electron repulsive forces between them dominate the fvan derwaais term The resulting destabilization is called van der Waals strain... 

Forces of Adsorption. Adsorption may be classified as chemisorption or physical adsorption, depending on the nature of the surface forces. In physical adsorption the forces are relatively weak, involving mainly van der Waals (induced dipole—induced dipole) interactions, supplemented in many cases by electrostatic contributions from field gradient—dipole or —quadmpole interactions. By contrast, in chemisorption there is significant electron transfer, equivalent to the formation of a chemical bond between the sorbate and the soHd surface. Such interactions are both stronger and more specific than the forces of physical adsorption and are obviously limited to monolayer coverage. The differences in the general features of physical and chemisorption systems (Table 1) can be understood on the basis of this difference in the nature of the surface forces. 

Dipole/induced-dipole and dipole-dipole attractive forces make alcohols higher boiling than alkanes of similar molecular weight. The attractive force between —OH groups is called hydrogen bonding. 

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. 

Finally, a fourth motivation for exploring gas solubilities in ILs is that they can act as probes of the molecular interactions with the ILs. Information can be discerned on the importance of specific chemical interactions such as hydrogen bonding, as well as dipole-dipole, dipole-induced dipole, and dispersion forces. Of course, this information can be determined from the solubility of a series of carefully chosen liquids, as well. FLowever, gases tend to be of the smallest size, and therefore the simplest molecules with which to probe molecular interactions. 

Where FCl is the solute gas-liquid partition coefficient, r is the tendency of the solvent to interact through k- and n-electron pairs (Lewis basicity), s the contribution from dipole-dipole and dipole-induced dipole interactions (in molecular solvents), a is the hydrogen bond basicity of the solvent, b is its hydrogen bond acidity and I is how well the solvent will separate members of a homologous series, with contributions from solvent cavity formation and dispersion interactions. 

There are several, separate types of interaction in III both covalent bonds and dipoles. Induced dipoles involve a partial charge, which we called <5+ or S, but, by contrast, covalent bonds involve whole numbers of electrons. A normal covalent bond, such as that between a hydrogen atom and one of the carbon atoms in the backbone of III, requires two electrons. A double bond consists simply of two covalent bonds, so four electrons are shared. Six electrons are incorporated in each of the rare instances of a covalent triple bond . A few quadruple bonds occur in organometallic chemistry, but we will ignore them here. 

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. 

In this chapter, you have learned about intermolecular forces, the forces between atoms, molecules, and/or ions. The types of intermolecular forces include ion-dipole forces, hydrogen bonding, ion-induced and dipole-induced forces, and London (dispersion) forces. 

Three MM programs are reported to be able to handle metal chelates (Table 10). Those originating from Boyd s force field do not consider nonbonded interactions beyond 1.2 times the sum of the van der Waals radii (218-221). Rasmussen s version of CFF is much more sophisticated (33,222). However, none of them explicitly considers induced bond dipoles in chelate ions that contain a number of highly polar bonds. This is probably why the previous calculations of metal chelates only compare closely related isomeric structures having the same metal ion. 

Attractive or repulsive forces between molecular entities or groups within the same molecular entity (i.e., both intermolecular and intramolecular) not due to bond formation or to electrostatic interactions of ions or ionic groups with one another or with neutral molecules. The origin of van der Waals forces is in electric polarization of uncharged atoms, groups, or molecules and includes dipole-dipole interactions, dipole-induced dipole interactions, and London forces (induced dipole-induced dipole interactions). 

These interactions (dipole-dipole, dd dipole-induced dipole, di and induced dipole-induced dipole, ii) are a function of dipole moment and polarizability. It has been shown that the dipole moment cannot always be replaced entirely by the use of electrical effect substituent constants as parameters ". This is because the dipole moment has no sign. Either an overall electron donor group or an overall electron acceptor group may have the same value of fi. It has also been shown that the bond moment rather than the molecular dipole moment is the parameter of choice. The dipole moments of MeX and PhX were taken as measures of the bond moments of substituents bonded to sp and sp hybridized carbon atoms, respectively, of a skeletal group. Application to substituents bonded to sp hybridized carbon atoms should require a set of dipole moments for substituted ethynes. 

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