Moments and Molecular Geometry

From the point of view of the chemist, dipole moments have been most important in indicating the shapes of simple molecules. The molecules CO2, CS2, HgCl2, and HgBr2 have zero dipole moments, whereas the molecules H20, S02, and (CgHs Te have dipole moments between 1.0 and 2.0 D units, indicating that the latter three molecules are bent, whereas the first four are linear. Sometimes the presence of a dipole is represented on the structural formula of a molecule by an arrow, pointing from the more positive end of the molecule to the more negative end. Thus  

Note that although the dipole moment of (CeHs Te has been measured, there is some doubt as to which end is positive. 

The very small permanent dipoles associated with CO (0.1 Z ), NO (0.1 D), and N 0 (0.14 D) indicate that although these molecules are not symmetric, the electron density is spread over the entire molecule in such a way that polarity is almost completely destroyed. 

In a few cases, dipole moment measurements have been used to distinguish cis from trans isomers. The more symmetric trans compounds often have dipole moments equal to or close to zero. The following three pairs of isomers have been distinguished by their dipole moments  

Although a number of octahedral complexes have been isolated in both cis and trans modifications, confirmations of configurations using dipole moment data have not been carried out. A large majority of such com- 

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The semiempirical MNDO SCF-MO and AMI SCF-MO models introduced by Dewar et al. (77JA4899 85JA3902) have proved to be suitable tools for reproducing experimental data for several examples of heterocyclic betaines of general type 1, such as dipole moments and molecular geometries. Relevant results are collected in Table IX and C). 

Relationship between dipole moment and molecular geometry is given in table 1.8. 

Relating dipole moment and molecular geometry State what geometries of a molecule AX are consistent with the information that the molecule has a nonzero dipole moment. (EXAMPLE 10.3)... 

St.-Amant, A., W. D. Cornell, P. Kollman, and T. A. Halgren. 1995. Calculation of Molecular Geometries, Relative Conformation Energies, Dipole Moments, and Molecular Electrostatic Potential Fitted Charges of Small Organic Molecules of Biochemical Interest by Density Functional Theory. J. Comp. Chem. 16, 1483. 

St.-Amant A, Cornell WD, Kollman PA, Halgren TA (1995) Calculation of molecular geometries, relative conformational energies, dipole-moments, and molecular electrostatic potential fitted charges of small organic-molecules of biochemical interest by density-functional theory, J Comput Chem, 16 1483-1506... 

A simpler approach, typically employed for small symmetric molecules, is to estimate ideal point multipoles by integration over the orbitals resulting from the calculated electron density distribution. The accuracy of the calculated moments is highly dependent on the basis set, electron correlation, and molecular geometry [19]. The MP2 level of theory with the 6-3IG polarizable basis set is broadly applied in such calculations. In order to save computational effort, MP2 is often executed as a single point calculation for a geometry determined on the basis of a lower level of theory. 

Dipole Moments In a diatomic molecule the difference in the electronegativities of bonding atoms results in a polar bond and a dipole moment. The dipole moment of a molecule made up of three or more atoms depends on both the polarity of the bonds and molecular geometry. Dipole moment measurements can help us distinguish between Afferent possible geometries of a molecule. 

The parameters to be used in MNDO were obtained using experimental data on 34 compounds. The parameters were optimized to reproduce observed heats of formation, dipole moments, ionization potentials, and molecular geometries. 

Calculation of Molecular Geometries, Relative Conformational Energies, Dipole Moments, and Molecular Electrostatic Potential Fitted Charges of Small Organic Molecules of Biochemical Interest by Density Functional Theory. 

Relationship Between Molecular Geometry and Dipole Moment Formula Molecular Geometry Dipole Moment ... 

The types of reference data used should reflect the properties that the method is designed to model. Among the more important of these properties are the molecular geometry, heat of formation (A/ff), dipole moment, and ionization potential. Heats of formation and molecular geometry data provide essential information on the energetics involved. No ideal experimental resource exists that can be used in defining the electron density distribution. X-ray structures provide almost complete information on where the electrons are, but the data are not in a form suitable For use in parameterization. The only... 

DIPOLE MOMENTS Determining Charge Separation Bond Polarity and Molecular Geometry... 

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