Potential energy Keesom

Keesom relationship phys chem An equation for the potential energy associated with the interaction of the dipole moments of two polar molecules. ka-sam ri la-sh3n,ship ... 

Dividing Equation (34) through by gives the fractional contribution made to the total attraction by the Debye (D), Keesom (K), and London (L) components of potential energy ... 

Keesom, Debye, and London contributed much to our understanding of forces between molecules [111-113]. For this reason the three dipole interactions are named after them. The van der Waals4 force is the Keesom plus the Debye plus the London dispersion interaction, thus, all the terms which consider dipole-dipole interactions Ctotai = Corient+Cind- -Cdisp. All three terms contain the same distance dependency the potential energy decreases with l/D6. Usually the London dispersion term is dominating. Please note that polar molecules not only interact via the Debye and Keesom force, but dispersion forces are also present. In Table 6.1 the contributions of the individual terms for some gases are listed. 

Table 6.1 Contributions of the Keesom, Debye, and London potential energy to the total van der Waals interaction between similar molecules as calculated with Eqs. (6.6), (6.8), and (6.9) using Ctotal = Corient + Cind + Cdisp- They are given in units of 10-79 Jm6. For comparison, the van der Waals coefficient Cexp as derived from the van der Waals equation of state for a gas (P + a/V fj (Vm — b) = RT is tabulated. From the experimentally determined constants a and b the van der Waals coefficient can be calculated with Cexp = 9ab/ (47T21V ) [109] assuming that at very short range the molecules behave like hard core particles. Dipole moments /u, polarizabilities a, and the ionization energies ho of isolated molecules are also listed.

D18.4 There are three van der Waals type interactions that depend upon distance as l/r6 they are the Keesom interaction between rotating permanent dipoles, the permanent-dipole-induced-dipole-interaction, and the induced-dipole-induced-dipole, or London dispersion, interaction. In each case, we can visualize the distance dependence of the potential energy as arising from the Mr dependence of the field (and hence the magnitude of the induced dipole) and the Mr3 dependence of the potential energy of interaction of the dipoles (either permanent or induced). 

The strongest van der Waals forces are those between molecules which have permanent dipoles. They are also known as Keesom forces. The potential energy... 

Table 6 summarizes the radial dependence and the order of magnitude of the potential energy of the most common multipolar interactions distinguishing, for the dipole-dipole case, stationary molecules at a fixed distance r (as in solids) from rotating molecules (as in liquids and gases also called Keesom interactions). 

Intermolecular forces between molecules result from interactions between their corresponding electron orbitals. The principal non-bonding interactions result from induced dipole-induced dipole (London), dipole-induced dipole (Debye) and dipole-dipole (Keesom) interactions. The intermolecular potential energy function, U, for each of these three types of interactions is of the same form. Here, r is the separation distance between bodies. 

Table 2.1 Contributions of the Keesom, Debye, and London potential energy to the total van der Waals interaction between similar molecules as calculated with Eqs. (218),(220), and (2.21) using...

The effect of the polarisability. and of the ionization potential IP may be directly related to their impact on the energy of the dispersive forces (London, Debye and Keesom) which govern physical adsorption onto activated carbon [4]. The lower positive effect of the molar mass M may be related to the influence of the molecular overcrowding which increases the surface contact with the solid, leading to more intensive interactions. 

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