Molecular orbital analysis

A TT MOLECULAR ORBITAL ANALYSIS OF THE DIELS-ALDER REACTION... 

Huckel realized that his molecular orbital analysis of conjugated systems could be extended beyond neutral hydrocarbons He pointed out that cycloheptatrienyl cation also called tropyhum ion contained a completely conjugated closed shell six tt electron sys tern analogous to that of benzene... 

The anomeric effect is best explained by a molecular orbital analysis that is beyond the scope of this text. 

Fig. 3.26 Frontier molecular orbital analysis for the Simmons-Smith cyclopropanation. [Dargel, T.K. Koch, W.J. Chem. Soc., Perkin Trans. 1996, 2, 877. Reproduced by pemiission of The Royal Society of Chemistry]...

The ground states of P/ [26, 27] and As " [28] have D structures. Molecular orbital analysis revealed that the square planar dianion exliibits the characteristic... 

In a, P-unsaturated carbonyl compounds and related electron-deficient alkenes and alkynes, there exist two electrophilic sites and both are prone to be attacked by nucleophiles. However, the conjugated site is considerably softer compared with the unconjugated site, based on the Frontier Molecular Orbital analysis.27 Consequently, softer nucleophiles predominantly react with a, (i-unsaturated carbonyl compounds through conjugate addition (or Michael addition). Water is a hard solvent. This property of water has two significant implications for conjugate addition reactions (1) Such reactions can tolerate water since the nucleophiles and the electrophiles are softer whereas water is hard and (2) water will not compete with nucleophiles significantly in such... 

These ohservations confirm the molecular orbital analysis of the E, state... 

FIGURE 23. Molecular orbital analysis of the TS of the dimerization of hthium(alkoxy)silylenoid. Orbital correlation energy diagram ( ove) and molecular orbitals of HOMO (TS, TS(L) and TS(R)), HOMO-1 (TS) and cr -(Si2-02) (TS(R)) (below). Reprinted with permission from Reference 26. Copyright 1998 American Chemical Society... 

Scheme 17.34 Molecular orbital analysis of putative metallo-nitrene.

Molecular orbital analysis of diatomic and triatomic fragments... 

The sequence of energy levels obtained from a simple molecular orbital analysis of an octahedral complex is presented in Fig. 1-12. The central portion of this diagram, with the t2g and e levels, closely resembles that derived from the crystal field model, although some differences are now apparent. The t2g level is now seen to be non-bonding, whilst the antibonding nature of the e levels (with respect to the metal-ligand interaction) is stressed. If the calculations can be performed to a sufficiently high level that the numerical results can be believed, they provide a complete description of the molecule. Such a description does not possess the benefit of the simplicity of the valence bond model. 

The simple crystal field analysis of the effect of ligands on transition metal d-electron energies accords well with the deeper molecular orbital analysis (see e.g. [99]). In what way(s), however, is the crystal field method unrealistic ... 

---