Molecular orbitals HOMO and LUMO

Next, examine the highest-occupied and lowest-unoccupied molecular orbitals (HOMO and LUMO) of dichlorocarbene. Were the reaction a nucleophilic addition , how would you expect CCI2 to approach propene Were the reaction an electrophilic addition , how would you expect CCI2 to approach propene Which inteqDretation is more consistent with the geometry of the transition state ... 

Examine and describe both the highest-occupied and lowest-occupied molecular orbitals (HOMO and LUMO, respectively) oiground state acetone. On which atom(s) is the HOMO primarily concentrated Is it in the o system or in the 7t system Repeat your analysis for the LUMO. 

Figure 1.8 Symmetry and energy of fixrntier molecular orbital (HOMO and LUMO)...

In view of their similarity the heterobenzenes may be treated as perturbed benzenes. Figure 4 illustrates the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of benzene. In the C2v symmetry of the heterobenzenes these orbitals split into iion-degenerate a2- and bt-orbitals. To the first approximation replacement of by a heteroatom E should leave the a2-orbitals unchanged since they have a node at this position. However, the bj-orbitals which have an antinode at the heteroatom should be strongly effected. 

The distribution of 77 electrons over the 77 MOs is regulated by the Aufbau principle and the Pauli rule. The only occupied MO of an MO diagram or the highest occupied MO thereof is called the HOMO (highest occupied molecular orbital). The only unoccupied MO of an MO diagram or the lowest unoccupied MO thereof is called the LUMO (lowest unoccupied molecular orbital). HOMOs and LUMOs are the so-called frontier orbitals since they flank the borderline between occupied and unoccupied orbitals. 

Figure 8.16 Frontier molecular orbitals (HOMO and LUMO) of a reactant molecule.

The degeneracies of the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs, respectively). 

FIGURE 4.3 The paradigmatic in silica spectra of the first three highest occupied and lowest unoccupied molecular orbitals HOMOs and LUMOs illustrating the respective, successive, ionization and affinities energies as provided by Koopmans theorem. Note KT implies ionization and affinity of one electron on successive levels and not of successive electrons on levels- see the marked occupied and virtual spin-orbitals (Putz, 2013). 

For example, the molecular orbitals (HOMO and LUMO) of a single molecule can be visualized, as shown in Figure 7.2 [21]. 

---