Partial charge dipole moment

Total positive partial charge Dipole moment from partial charges Kier and Hall molecular shape indices Solvent-accessible surface area... 

Arises from instantaneous partial charges instantaneous dipole moment) in one molecule inducing partial charges (dipole moment) in a neighboring one Exists between atoms and rotating molecules as well Strength depends on polarizability and shape of molecule. 

Electronics/charge (formal charge, partial atom charges, dipole moment and vectors, HOMO and LUMO energy, F and R snbstitnent constants, etc.)... 

A dipole moment is a vector quantity that measures the separation of electrical charge. Dipole moments have units of electrical charge (a fuU plus or minus charge corresponding to 4.80 x 10 ° esu) times distance, and they are usually expressed in units of debye (D), with 1 D = 10 esu cm. ° Thus, a system consisting of two atoms, one with a partial charge of + 0.1 and the other a partial charge of —0.1, located 1.5 A apart would have a dipole moment of... 

Carbon-oxygen and carbon-halogen bonds are polar covalent bonds and carbon bears a partial positive charge in alcohols ( " C—0 ) and in alkyl halides ( " C—X ) Alcohols and alkyl halides are polar molecules The dipole moments of methanol and chloromethane are very similar to each other and to water... 

Electronegativity is a measure of the pulling power of an atom on the electrons in a bond. A polar covalent bond is a bond between two atoms with partial electric charges arising from their difference in electronegativity. The presence of partial charges gives rise to an electric dipole moment. 

Figure 12-5 illustrates the solvation of Na and Cl" ions as NaCl dissolves in water. A cluster of water molecules surrounds each ion in solution. Notice how the water molecules are oriented so that their dipole moments align with charges of the ions. The partially negative oxygen atoms of water molecules point toward Na cations, whereas the partially positive hydrogen atoms of water molecules point toward Cl" anions. 

In the present work, we shall investigate the problem of the amount of correlation accounted for in the DF formalism by comparing the molecular electrostatic potentials (MEPs) and dipole moments of CO and N2O calculated by DF and ab initio methods. It is indeed well known that the calculated dipole moment rf these compounds is critically dependent on the level of theory implemented and, in particular, that introduction of correlation is essential for an accurate prediction [13,14]. As the MEP property reflects reliably the partial charges distribution on the atoms of the molecule, it is expected that the MEP will exhibit a similar dependence and that its gross features correlate with the changes in the value of dipole moment when switching from one level of theory to the other. Such a behavior has indeed been reported recently by Luque et al. [15], but their study is limited to the ab initio method and we found it worthwhile to extend it to the DF formalism. Finally, the proton affinity and the site of protonation of N2O, as calculated by both DF and ab initio methods, will be reported. 

Values for the partial charges of atoms can be derived from quantum mechanical calculations, from the molecular dipole moments and from rotation-vibration spectra. However, often they are not well known. If the contribution of the Coulomb energy cannot be calculated precisely, no reliable lattice energy calculations are possible. 

The dipole moment of a molecule can be obtained from a measurement of the variation with temperature of the dielectric constant of a pure liquid or gaseous substance. In an electric field, as between the electrostatically charged plates of a capacitor, polar molecules tend to orient themselves, each one pointing its positive end toward the negative plate and its negative end toward the positive plate. This orientation of the molecules partially neutralizes the applied field and thus increases the capacity of the capacitor, an effect described by saying that the substance has a dielectric constant greater than unity (80 for liquid water at 20°C). The dipole moments of some simple molecules can also be determined very accurately by microwave spectroscopy. 

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