Highest-energy occupied molecular orbitals

The most important molecular- orbitals are the so-called frontier molecular- orbitals. These are the highest (energy) occupied molecular- orbital (HOMO), and lowest (energy) unoccupied molecular- orbital (LUMO). The following picture shows the LUMO surface for the hydrogen molecule, H2. The LUMO consists of two separate surfaces, a red... 

The highest-energy occupied molecular orbital (HOMO) and the lowest-energy unoccupied molecular orbital (LUMO) of a particular molecular entity. The HOMO can be completely or partially filled whereas the LUMO can be completely or partially vacant. The frontier orbital method allows one to interpret reaction behavior by studying HOMO and LUMO overlaps between reacting entities. 

Lever has successfully predicted Mn"/ potentials of 24 Mn-carbonyl complexes containing halide, pseudohalide, isonitrile, and phosphine co-ligands, with additivity parameters derived from the potentials of Ru "/" couples [39]. An important consideration for heteroleptic complexes is the influence of isomerism on redox thermodynamics. For Mn(CO) (CNR)6- complexes, with n = 2 or 3, the Mn"/ potentials for cis/trans and fac/mer pairs differ by as much as 0.2 V [40]. The effect arises from the different a-donor and 7r-acceptor abilities of carbonyl (CO) and isocyanide and their influence on the energy of the highest energy occupied molecular orbital (HOMO). 

Excitation in general consists in promotion of an electron from one of the highest-energy occupied molecular orbitals (HOMOs) to achieve one of the lowest-energy unoccupied molecular orbitals (LUMOs) of the ground-state molecule. This may be expressed, for example, by the terms (n, 7i ), (n, a ), (n, tt ), or (n, a ), whereas the multiplicity is shown as a prefix, eg 1(n, if ). Population of the antibonding excited states thus usually results in bond weakening. 

HOMO highest energy occupied molecular orbital KDO 3-deoxy-D-ma o-2-octulosonic acid... 

Use SpartanView to display the two highest-energy occupied molecular orbitals of acetylene. How do they differ ... 

Suppose we remove an electron from the highest energy occupied molecular orbital in CO2. Is the dissociation energy of the resulting ion larger or smaller than that of CO2 How will the C—O bonds change Explain your answers. 

Highest Energy Occupied Molecular Orbital (HOMO)... 

To explain the pericychc reaction of 1,3,5-hexatriene by frontier molecular orbital theory, we need only consider the symmetry of 713 and 714. The HOMO is 713 it is symmetric. The LUMO is 714 it is antisymmetric. Note that this order of symmetry is opposite to that of 1,3-butadiene. The symmetry of the HOMO alternates with each additional double bond. The difference in the chemistry of polyenes noted earlier in this chapter for An 71 and 4 + 2 7t systems results from this difference in symmetry for the highest energy occupied molecular orbital involved in the reaction (Figure 25.3). 

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