Density-electrostatic potential LUMO maps

This chapter introduces a number of useful graphical models, including molecular orbitals, electron densities, spin densities, electrostatic potentials and local ionization potentials, and relates these models both to molecular size and shape and molecular charge distributions. The chapter also introduces and illustrates property maps which simultaneously depict molecular size and shape in addition to a molecular property. Properties include the electrostatic potential, the value of the LUMO, the local ionization potential and the spin density. 

Although the most important, the electrostatic potential is not only the quantity which when mapped onto an electron density surface may provide useful chemical information. Maps of certain key molecular orbitals, in particular, the HOMO and LUMO, may also lead to informative models. Consider, for example, a map of the (absolute) value of the lowest-unoccupied molecular orbital (LUMO) in cyclohexanone, two views of which are shown below. 

Property Map. A representation or map of a property on top of an Isosurface, typically an Isodensity Surface. Electrostatic Potential Maps, and HOMO and LUMO Maps and Spin Density Maps are useful property maps. 

Part Three. The benzyl (and allyl) halides are a special case they have resonance. To see how the charge is delocalized in the benzyl carbocation, request two plots the electrostatic potential mapped onto a density surface and the LUMO mapped onto a density surface. Submit these for calculation at the AMI semiempirical level. On a piece of paper, draw the resonance-contributing structures for the benzyl cation. Do the computational results agree with the conclusions you draw from your resonance hybrid ... 

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See also in sourсe #XX -- [ ]

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