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MO, Delocalized

The calculations showed that the C=C w-MO ionization in cyclopropene (9.86 eV) correlates most closely with the second ionization level in cyclopropenone and not with the first band. It is stressed that the noticably high dipole moment of cyclopropenone represents a manifestation of the extreme MO delocalization. [Pg.46]

The MO delocalization energy (DE) calculated using a simple LCAO approach indicated that pyran-4-one (DE, 2.868/8) possesses greater aromaticity than benzene (DE 2/8) (62CCC1242). Subsequent more refined calculations gave substantially lower values, but still indicated considerable aromaticity for pyran-4-one. Values of DE, DEsp and aromaticity indices for pyran-4-one and chromone which were obtained using various MO methods are presented in Table 9. [Pg.637]

There may be a relatively large charge separation, e.g. in MoSj- and almost equal net charges on the metal and sulfur atoms, e.g. in [Mo2S(CN),2]6-. 78a MO calculations on the latter ion show that there are k MOs delocalized over three centers. Resonance Raman studies further indicate that the delocalization extends over the whole linear N—C—Mo—S—Mo—C—N system. The tt(S) -> t/(Mo) donation induces a decrease of electron density on the sulfur and is, therefore, responsible for an unusual charge transfer transition Mo-+S (band at 27100cm-1), quite the reverse assignment to that in examples with terminal sulfide where a considerable p contribution also has to be anticipated (see Table l).3,4... [Pg.524]

MOs delocalized (occupied) over the metal centers M and M occur particularly clearly in complexes with M S2MS2M units (e.g. with M = Fe, and notably also when M = Cu1 with a closed d-shell cf. the results of the resonance Raman spectra mentioned below). [Pg.574]

For benzo[. ]thiophene, there is a it-MO delocalization between the two aromatic rings. For benzo[r]thiophene, the orbitals of the five-membered rings are localized on the heteroatom, C-1 and C-3, and there is no it-MO delocalization on the heterocyclic five-membered rings. These results are in agreement with the theoretical aromaticity of these molecules as are theoretical results from the reactivity indexes. [Pg.696]

The aromatic hydrocarbons are conjugated cyclic structures in which the 77 bonding is described by delocalized MOs. Each carbon atom has sp hybrid orbitals that overlap to form C —C cr bonds that define the molecular framework. The remaining nonhybridized p orbitals combine to give 77 MOs delocalized over the entire molecule. [Pg.307]

The resulting MOs are symmetry MOs, delocalized over the entire molecule. As it will be shown for H20, a description more adherent to the chemical picture of four localized C—H bonds can be obtained in terms of the orthogonal transformation16 connecting occupied MOs, the first relation being ... [Pg.64]

Wheland45 demonstrated the relationship between MO delocalization energy of hydrocarbons and their acidity, and on this basis Streitwieser46... [Pg.268]

The concept of localized MOs is not as widely applicable as that of delocalized canonical MOs. Delocalized MOs are valid for any molecule. However (as noted in Section 11.5), the Hartree-Fock wave functions of nonclosed-shell electronic states are, in most cases, linear combinations of several Slater determinants [for example, see (10.44) and (10.45)], and the above localization procedure does not apply to the open-shell orbitals in these wave functions. Thus, in a molecule in an excited electronic state with an open-shell configuration, the electrons in the incompletely filled MOs are delocalized over much of the molecule. [Pg.517]

By balancing calculated values of angle strain against MO delocalization energy as a function of configuration, it has been possible to predict the relative stability and geometry of some interesting postulated reaction intermediates. [Pg.87]

The concept of localized MOs is not as widely applicable as that of delocalized canonical MOs. Delocalized MOs are valid for any molecule. However (as noted in Section 11.5),... [Pg.469]

Molecular orbital (MO) theory treats a molecule as a collection of nuclei with MOs delocalized over the entire structure. [Pg.345]


See other pages where MO, Delocalized is mentioned: [Pg.633]    [Pg.720]    [Pg.633]    [Pg.288]    [Pg.141]    [Pg.91]    [Pg.1170]    [Pg.116]    [Pg.58]    [Pg.69]    [Pg.72]    [Pg.712]    [Pg.274]    [Pg.68]    [Pg.32]    [Pg.236]    [Pg.69]    [Pg.141]    [Pg.361]    [Pg.361]    [Pg.275]   
See also in sourсe #XX -- [ Pg.32 , Pg.34 , Pg.36 ]




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Orbital (MO) Theory and Electron Delocalization

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