Molecular dipole moment, calculation

In the gas phase H2SO4 and D2SO4 adopt the C conformaiion with r(O-H) 97 pm. r(S-OH) 157.4 pm, r(S-O) 142.2 pm the various jnleralamjc and dihedral angles were also determined and the molecular dipole moment calculated to be 2.73... 

Rashin, A. A., L. Young, I. A. Topol, and S. K. Burt. 1994. Molecular dipole moments calculated with density functional theory. Chem. Phys. Lett. 230, 182. 

Exploiting the charge transfer information encoded by the matrix CT, the algebraic semisum charge-transfer index, denoted as p. g, was proposed as a measure of the molecular dipole moment calculated as the half-sum of the GTy elements corresponding to pairs of bonded... 

In contrast with condensed phases, intermolecular interactions in gases are negligibly small. The dipole moment found in the gas phase at low pressure is usually accepted as the correct value for a particular isolated molecule. The molecular dipole moment calculated for pure liquid using Debye s model gives values which are usually very different from those obtained from gas measurements. Intermolecular interactions in liquids produce deviations from Debye s assumptions. 

Molecular dipole moments are often used as descriptors in QPSR models. They are calculated reliably by most quantum mechanical techniques, not least because they are part of the parameterization data for semi-empirical MO techniques. Higher multipole moments are especially easily available from semi-empirical calculations using the natural atomic orbital-point charge (NAO-PC) technique [40], but can also be calculated rehably using ab-initio or DFT methods. They have been used for some QSPR models. 

The angles ot, p, and x relate to the orientation of the dipole nionient vectors. The geonieti y of interaction between two bonds is given in Fig. 4-16, where r is the distance between the centers of the bonds. It is noteworthy that only the bond moments need be read in for the calculation because all geometr ic features (angles, etc.) can be calculated from the atomic coordinates. A default value of 1.0 for dielectric constant of the medium would normally be expected for calculating str uctures of isolated molecules in a vacuum, but the actual default value has been increased 1.5 to account for some intramolecular dipole moment interaction. A dielectric constant other than the default value can be entered for calculations in which the presence of solvent molecules is assumed, but it is not a simple matter to know what the effective dipole moment of the solvent molecules actually is in the immediate vicinity of the solute molecule. It is probably wrong to assume that the effective dipole moment is the same as it is in the bulk pure solvent. The molecular dipole moment (File 4-3) is the vector sum of the individual dipole moments within the molecule. 

Essentially all experimentally measured properties can be thought of as arising through the response of the system to some externally applied perturbation or disturbance. In turn, the calculation of such properties can be formulated in terms of the response of the energy E or wavefunction P to a perturbation. For example, molecular dipole moments p are measured, via electric-field deflection, in terms of the change in energy... 

Which one of the dichlorobenzene isomers does not have a dipole moment" Which one has the largest dipole moment" Compare your answers with the dipole moments calculated using the molecular modeling software in Learning By Modeling... 

Molar absorptivity (Section 13 21) Ameasure of the intensity of a peak usually in UV VIS spectroscopy Molecular dipole moment (Section 1 11) The overall mea sured dipole moment of a molecule It can be calculated as the resultant (or vector sum) of all the individual bond di pole moments... 

The molecular dipole moment is perhaps the simplest experimental measure of charge density in a molecule. The accuracy of the overall distribution of electrons in a molecule is hard to quantify, since it involves all of the multipole moments. Experimental measures of accuracy are necessary to evaluate results. The values for the magnitudes of dipole moments from AMI calculations for a small sample of molecules (Table 4) indicate the accuracy you may... 

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. 

Jasien, P. G., and G. Fitzgerald. 1990. Molecular dipole moments and polarizabilities from local density functional calculations Applications to DNA base pairs. J. Chem. Phys. 93, 2554. 

Since the parameters used in molecular mechanics contain all of the electronic interaction information to cause a molecule to behave in the way that it does, proper parameters are important for accurate results. MM3(2000), with the included calculation for induced dipole interactions, should model more accurately the polarization of bonds in molecules. Since the polarization of a molecular bond does not abruptly stop at the end of the bond, induced polarization models the pull of electrons throughout the molecule. This changes the calculation of the molecular dipole moment, by including more polarization within the molecule and allowing the effects of polarization to take place in multiple bonds. This should increase the accuracy with which MM3(2000) can reproduce the structures and energies of large molecules where polarization plays a role in structural conformation. 

There is no simple explanation for the much more pronounced instability to pressure of CO compared to N2. Since the only structural difference arises from the heteroatomic character of CO, one could expect that the molecular dipole moment increases with pressure leading to a higher compressibility of CO. But no evidence for this is obtained from either the ab initio calculation or experimentally. In fact the equation of state of nitrogen and carbon monoxide are practically coincident in the pressure range of interest. One other point of interest is the head-to-tail disorder present in carbon monoxide because it has been observed in several high pressure experiments that defects and disorder can play an important role. 

In the case that the three components of the molecular dipole moment are to be evaluated for subsequent calculation of its direction, D becomes a 3 x 8N matrix, and the result of Eq. (7.42) is the 3 x 3 variance-covariance matrix M of the components. 

The solid-state molecular dipole moment has been evaluated in a recent HF calculation on the crystal of urea. The result of 23.5-10 30 Cm, compared with... 

Villar et al. developed an atomic hydrophobicity contribution that depends on the molecular conformation. The hydrophobicity parameters were calculated by including charge densities, atomic contributions to the total molecular surface area and the molecular dipole moment [47, 48]. This method is implemented in the SPARTAN software. 

The deformed-chair conformation of ring A in a 4,4-dimethyl-3-oxo-5or-steroid has been confirmed by an X-ray study of a 17 -benzoyloxyandrostane derivative. The results agree with those of an earlier study of the 17-iodoacetate, and with the geometry indicated by force-field calculations. Dipole moments calculated by the application of molecular mechanics to 5a-androstane-3,17-dione and its distorted 4,4-dimethyl derivative are larger than those observed the reasons for these deviations are not yet clear. 

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