Hypervalent molecules dipole moments

Examine the charge on the methylidene group, as well as the magnitude and direction of the molecule s dipole moment. Are they consistent with representation of the ylide as a hypervalent molecule or as a zwitterion ... 

This chapter assesses the performance of quantum chemical models with regard to the calculation of the magnitudes of dipole moments. (Too little experimental information is available about the sign and/ or direction of dipole moments or about higher moments to make comparisons of these quantities with the results of calculations of value.) Coverage is divided according to type of molecule diatomics and small polyatomics, hydrocarbons, molecules with heteroatoms and hypervalent molecules. Models examined include Hartree-Fock... 

Table 10-6 Mean Absolute Errors in Dipole Moments for Hypervalent Molecules... 

Dipole moments for hypervalent molecules calculated from semi-empirical models are generally larger than experimental values (sometimes by a factor of two or more), suggesting descriptions which are too ionic. Figure 10-11 provides an overview for the PM3 model. Semi-empirical models should not be used. 

Table AlO-17 Dipole Moments in Hypervalent Molecules. Hartree-Fock Models ... 

Table AlO-20 Dipole Moments in Functional Models Hypervalent Molecules. BLYP Density ...

Clare, B.W. and Supuran, C.T. (1998) Semi-empirical atomic charges and dipole moments in hypervalent sulfonamide molecules descriptors in QSAR studies./. Mol. Struct. (Theochem), 428, 109—121. 

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