Group orbitals and

The origin of the preference for the eclipsed conformation of propene can be explained in MO terms by focusing attention on the interaction between the double bond and the n component of the orbitals associated with the methyl group. The dominant interaction is a repulsive one between the filled methyl group orbitals and the filled n orbital of the double bond. This repulsive interaction is greater in the bisected conformation than in the eclipsed conformation. ... 

Fig. 11.18 Identification of the symmetries of ligand group orbitals and metal orbitals involved in the o bonds (represented as vectors) of an octahedral MU. complex. The characters of the reducible representation, r, are derived by counting the number of vectors that remain unmoved under each symmetry operation of the Oi, point group The irreducible components of C, are obtained by application of Eq. 3.1-...

Fig. 11.24 Identification of the symmetries of ligand group orbitals and metal orbitals capaMf of participating in ir bonds (represented na vectors) in an octahedral Ml complex. The characters and irreducible components of the reducible representation, T,. were derived by application of the same methods used for the c-only system (Fig. 11.(8).

We deal here only with the CH group orbitals and do not consider the orbitals corresponding to the two other bonds of the carbon atom. Four AOs intervene in the CH bonds, the two hybrid carbon orbitals and the two s hydrogen orbitals. To find their linear combinations requires solving an equation of the fourth degree. We can get around the problem by taking the symmetry combinations of the carbon hybrids ... 

If the molecule does not have a central atom (e.g., C6H6), we begin with the second step, first forming different group orbitals and then combining them, if possible, into MOs. Examples will be given for both cases. 

The next MO will be of B u symmetry. This irreducible representation also appears in 1, 2, and 3. Take this time the corresponding 1 and 2 group orbitals and combine them into molecular orbitals ... 

Fig. 11.24 (denllfication of the symmetnes of ligand group orbitals and metal orbitals... 

Although both molecules have threefold symmetry, the procedure for describing molecular orbitals of BF3 differs from NH3, because the fluorine atoms surrounding the central boron atom have 2p as well as 2s electrons to be considered. In this case, the Py axes of the fluorine atoms are chosen so that they are pointing toward the boron atom and the Px axes are in the plane of the molecule. The group orbitals and their symmetry in the point group are shown in Figure 5-32. The molecular orbitals are shown in... 

Figure 3.15 Projections identifying the group orbitals and their irreducible symmetries for local o -orbital decoration of the vertices of the Oi2v orbit, Table 3.15, of a molecular structure with point symmetry. The icons "A", and are applied as in Figure 3.8.

For the linear azide ion, N3, sketch the group orbitals and determine which of these orbitals can interact with the valence orbitals of the central nitrogen. Classify the possible interactions as a, n, or nonbonding. 

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