Dipole moments of the bonds and the unshared electron pair in sulfites and sulfoxides

1969 ◽  
Vol 18 (3) ◽  
pp. 495-498
Author(s):  
L. K. Yuldasheva ◽  
R. P. Arshinova ◽  
S. G. Vul'fson
Keyword(s):  
Electron Pair ◽  
Dipole Moments ◽  
Unshared Electron Pair

A quantum-mechanical study of the water molecule

1960 ◽  
Vol 255 (1282) ◽  
pp. 367-381 ◽  
Keyword(s):  
Water Molecule ◽  
Electron Pair ◽  
Dipole Moments ◽  
Electron System ◽  
Effective Field ◽  
Orbital Function ◽  
Self Consistent Field ◽  
Quantum Mechanical Study ◽  
The One ◽  
Pair Function

Non-empirical calculations of the electronic structure of the water molecule (treated as a full ten-electron system) are carried out for various types of wave function. These include a ‘bond orbital’ function, a ‘modified electron-pair’ function, and various Roothaan-type self-consistent field (s. c. f.) functions. These approximations are refined by admitting interaction with up to twelve configurational functions of ground-state symmetry. Three bond angles are considered. The results show that the modified electron pair function, which has not hitherto been used in non-empirical calculations, provides the most satisfactory first approximation. This function is constructed from orthonormalized hybrid orbitals in order to overcome non-orthogonality difficulties; and the inclusion of configuration interaction in this particular basis is found to be simple, effective and physically meaningful. The concept of a ‘core’, comprising the oxygen inner shell and lone pairs and providing an effective field for the bond pairs, is found to be remarkably satisfactory. Provided the effective field is properly defined, it is then possible to treat the molecule formally as a four-electron system and to obtain, nevertheless, a total energy 0⋅3 eV better than that given by the best of the s. c. f. calculations. This suggests that the ‘core approximation’ is not a real obstacle to progress. The one-electron density matrices are calculated from the various wave functions and the corresponding dipole moments are evaluated.

Molecular Geometries, Hybridizations and Polarities

2013 ◽  
pp. 48-57
Keyword(s):  
Molecular Modeling ◽  
Molecular Species ◽  
Electron Pair ◽  
Dipole Moments ◽  
Three Dimensions ◽  
Semiempirical Methods ◽  
Valence Shell ◽  
Trigonal Bipyramidal ◽  
Shell Electron ◽  
Square Planar

In this exercise, the basics of Valence Shell Electron Pair Repulsion (VSEPR) will be reviewed and the structures constructed using this approach will be visualized in three dimensions. Students will build molecules with geometries such as linear, trigonal planar, tetrahedral, trigonal bipyramidal, square planar, and octahedral. Students will identify the hybridizations of the various molecules constructed in the molecular modeling program. Students will utilize semiempirical methods to calculate the dipole moments of the molecular species constructed.

The gauche effect on conformation. α-Substituted sulfones and N-substituted sulfonamides

1979 ◽  
Vol 44 (11) ◽  
pp. 3378-3384 ◽  
Author(s):  
Otto Exner ◽  
Jan B. F. N. Engberts
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Benzene Solution ◽  
Dipole Moments ◽  
Conformational Preference ◽  
Electron Pairs ◽  
Gauche Effect

The dipole moments of α-halogenosulfones IIa-f in benzene solution revealed the conformation C, those of N-methyl-N-nitrosulfonamides IIIa-c the conformation F. In either case the conformational preference is governed by the gauche rule which may be worded in a modified version that symmetrical positions of polar bonds and/or of lone electron pairs are disfavoured. A lone electron pair appears to be more significant than a polar bond.

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