Non-bonding molecular orbital

It is well known that Hund s rule is applicable to atoms, but hardly so to the exchange coupling between two singly occupied molecular orbitals (SOMOs) of a diradical with small overlap integrals. Several MO-based approaches were then developed. Diradicals were featured by a pair of non-bonding molecular orbitals (NBMOs), which are occupied by two electrons [65-67]. Within the framework of Hiickel MO approximation, the relationship between the number of NBMOs,... 

There is an obvious analogy in orbital energy and symmetry between D3h and C4v structures since the Cs structure also has much the same pattern, it is evident that any interconversion of PHS is a symmetry-allowed process. The high-lying non-bonding molecular orbital (see Fig. 26) has its electron density on the exterior of the molecule, making it prone to attack by Lewis acids. 

The electrostatic potential surface for trimethylamine results from a single non-bonded valence molecular orbital (the HOMO), while the electrostatic potential surfaces for dimethyl ether and methyl fluoride result from a combination of two and three high-lying non-bonded molecular orbitals, respectively, i.e. 

Lone Pair. A Non-Bonded Molecular Orbital which is typically associated with a single atom. 

Non-Bonded Molecular Orbital. A molecular orbital which does not show any significant Bonding or Antibonding characteristics. A Lone Pair is a non-bonded molecular orbital. 

This weak transition is due to the promotion of an electron from the non-bonding molecular orbital n to an anti-bonding tt orbital. This transition is usually observed in molecules that contain a heteroatom as part of an unsaturated system. The most common of these bands corresponds to the carbonyl band at around 270 to 295 nm, which can be easily observed. The molar absorption coefficient for this band is weak. The nature of the solvent influences the position of absorption bands because the polarity of the bond is modified during absorption. For example, ethanal Amax = 293 nm (e = 12 in ethanol as solvent). 

For some special classes of BSs, explicit formulae for K were given by T. F. Yen [7] (1971). Using the coefficients of the non-bonding molecular orbitals (NBMO-s), W. C. Herndon [8] (1973) found an interesting method for calculating K which,... 

The determinant of the - adjacency matrix A. It was observed that this determinant is often equal to zero and this is a necessary and sufficient condition for the presence of non-bonding molecular orbitals in Hiickel theory. The actual numerical value of det A is correlated to the thermodynamic stability of the molecule [Graovac and Gutman, 1978 Trinajstic, 1992]. 

We have previously shown that classical structural formulae can be reproduced on the basis of molecular orbital theory. The stability associated with molecular structoes obeying the octet rule results from the fact that all bonding (and non-bonding) molecular orbitals are occupied. 

Three equivalent molecular orbitals almost localized in the three N-H bonds and an approximately non-bonding molecular orbital almost localized in the N atom. Since the bond angles (107°) are very close to those for the axes of sp atomic orbitals, the non-bonding orbital can be considered approximately as an sp hybrid orbital of N. Each one of the bonding molecular orbitals is approximately the combination of a Is orbital of H with an sp orbital of N. 

There exists a third class of pol3muclear compounds, including some polynuclear carbonyls, where the rule seems simply inapplicable. Either a bonding molecular orbital is so high in energy as to be unpopu-... 

The boron hydrides are called electron-deficient compounds because they are easily reduced by hydrogen. Incorrect boron hydrides are electron-deficient because they lack the electrons required to fill the bonding and non-bonding molecular orbitals. 

Simple molecular orbitals (eigenvectors) corresponding to x > 0, x < 0, and x = 0 are called bonding, antibonding, and non-bonding, respectively. Note that the number of linearly independent non-bonding molecular orbitals (NBMOs) is equal to the multiplicity of the number zero in the graph spectrum. This fact can be related to the stability of the... 

Fig. 17.7. Left a seven-center bonding molecular orbital in Te(CH3)(, or SFg formed by combination of the valence shell orbital of the central atom with a suitable AO on each of the six ligating atoms. Center and right two degenerate, non-bonding molecular orbitals formed by linear combination of atomic orbitals on the ligating atoms.

---