Lowest-energy molecular orbitals

The lowest energy molecular orbital of singlet methylene looks like a Is atomic orbital on carbon. The electrons occupying this orbital restrict their motion to the immediate region of the carbon nucleus and do not significantly affect bonding. Because of this restriction, and because the orbital s energy is very low (-11 au), this orbital is referred to as a core orbital and its electrons are referred to as core electrons. 

In Chapter 3,1 discussed the construction of simple LCAO-MOs for the hydrogen fflolecule-ion, starting from 1 s atomic orbitals on the hydrogen centres. Thus, we constructed LCAO-MO approximations to the two lowest energy molecular orbitals as... 

Electrons are accommodated in the lowest-energy molecular orbital, then in orbitals of increasingly higher energy. 

Figure 2.26 Lowest energy molecular orbital for benzene...

The complete calculation gives the result shown in Figure 21-9. Here the lowest-energy molecular orbital has a higher proportion of the p orbital of... 

The lowest-energy molecular orbital is entirely bonding, with constructive overlap between all pairs of adjacent p orbitals. There are no vertical nodes in this lowest-lying MO. 

The simplest compound that can have two conjugated Jt bonds is butadiene. As we would now expect, this is a planar compound that can adopt two different conformations by rotating about the single bond. Rotation is somewhat restricted (around 30 kj mol-1) but nowhere near as much as in an amide (typically 60-90 kj mol-1). What do the molecular orbitals for the butadiene Jt system look like The lowest-energy molecular orbital will have all the p orbitals combining in-phase. The next lowest will have one node, and then two, and the highest-energy molecular orbital will have three nodes (that is, all the p orbitals will be out-of-phase). 

The larger the number of bonding interactions, the lower in energy the MO. The lowest energy molecular orbital ( j/i) has all bonding interactions between the p orbitals. 

The four lowest energy molecular orbitals in this diagram result from bonding interactions between the a-donor orbitals of the ligands and the dj2-y2, d, p, and orbitals... 

The lowest energy molecular orbital (m.o.), named lsless than the value for the Is orbital of the... 

In this ion, the single pair of electrons occupies the lowest-energy molecular orbital, a bonding orbital distributed over all three atoms. This implies a bond... 

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