Electron distribution in compounds

In principle, the empirical group parameter methods can be used to aid molecular structure determination, but their principal use to date has been in the determination of the nature of bonding and the electron distribution in compounds by interpretation of the magnitudes of the empirically evaluated parameters. 

Most organic compounds are electrically neutral they have no net charge, either positive or negative. We saw in Section 2.1, however, that certain bonds within a molecule, particularly the bonds in functional groups, are polar. Bond polarity is a consequence of an unsymmetrical electron distribution in a bond and is due to the difference in electronegativity of the bonded atoms. 

The complex contains 72 atoms with 244 valence electrons distributed in 226 valence atomic orbitals. In order to reduce the computational effort, and to assess the contribution of the ligand 7r-orbitals to the overall spectrum, we examined a "reduced" model, see Figure 2, in which the benzene rings of the ligands are replaced by -HC=CH- groups. This model compound consists of... 

Fundamental advances are offered by the knowledge of energy states and their electronic distributions in organic compounds and the relationship of these to reaction mechanisms. The development, for example, of even an empirical and approximate general scheme for the estimation of activation energies would indeed be most notable. 

Several older theoretical studies are included in the review by Knowles <1996CHEC-II(7)489>, and little has been reported since. Nagy et al. carried out quantum calculations on several [l,2,3]triazolo[4,5-t/ pyridazines to reveal electron distributions in the ground and the excited state using the semi-empirical Hiickel molecular orbital (MO) method to explain the fluorescence of such compounds (see Section 10.13.3.2) <2002JPH83>. 

In the previous chapters we discussed electron distribution in organic molecules. In this chapter we discuss the three-dimensional structure of organic compounds.1 The structure may be such that stereoisomerism2 is possible. Stereoisomers are compounds made up of the same atoms bonded by the same sequence of bonds but having different three-dimensional structures which are not interchangeable. These three-dimensional structures are called configurations. 

Electron Distribution in Heterocycles , R. D. Brown, F. R. Burden and G. R. Williams, in Proceedings of the 2nd International Symposium on Quantum Aspects of Heterocyclic Compounds in Chemistry and Biochemistry , 1969, pp. 152-159. 

NaCl The bond in solid sodium chloride is a largely ionic one between Na+ and Cl-. In spite of what we ve said previously, though, experiments show that the NaCl bond is only about 80% ionic and that the electron transferred from Na to Cl still spends some of its time near sodium. A particularly useful way of visualizing this electron transfer is to represent the compound using what is called an electrostatic potential map, which uses color to portray the calculated electron distribution in the molecule. The electron-poor sodium atom is blue, while the electron-rich chlorine is red. 

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