Hydrogen frontier 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... 

It appears that supported metal catalysts can be used to promote synthetically useful organometallic reactions. The utilization of such reactions can be of practical, economic, and environmental importance to the fine chemical industry. Frontier Molecular Orbital and mechanistic considerations indicate that these reactions, along with hydrogenations and, presumably, oxygenations, take place on the coordinately unsaturated comer atoms present on the surface of these dispersed metal catalysts. 

The effects of hydrogen bonding were described in Section 3-4. In this section, the molecular orbital basis for hydrogen bonding is described as an introduction to the frontier molecular orbital approach to acid-base behavior. 

The frontier molecular orbital model for donor-acceptor complexes provides a convenient framework for a discussion of hydrogen bonding and receptor-guest interactions. 

Intermediate 5 is not isolated. It is transformed into the more stable dihydronaphthalene 2 by means of a thermal [1,5] sigmatropic hydrogen shift. This type of sigmatropic rearrangement can be understood in terms of the frontier molecular orbital theory considering the interaction between the H(ls) orbital and the LUMO ( l/3 ) of the diene component in the transition state (Fig. 14.2). A positive overlap between the orbitals where bond breaking and bond making takes place is produced when the H atom slides across the top face of the planar transition state. This kind of shift is called suprafacial. 

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