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Unformatted text preview: Chem 120A Huckel theory, band theory of solids (extra) 05/07/07 Spring 2007 Lecture 42 READING: Ratner and Schatz, Ch. 12 Atkins and Friedman, Ch. 8.12 Huckel Theory, continued Last time we introduced Huckel theory and applied it to benzene, showing that we get extra binding energy from constructing delocalized orbitals from all six p z atomic orbitals. Note that both and are negative. The ground state configuration of benzene is ( 1 a ) 2 ( 1 e ) 4 and the energy levels and orbitals are reproduced at the end of this lecture again, for easy reference. This construction of delocalized molecular orbitals can be carried out for any conjugated electron system, i.e., one which can be written with alternating double and single bonds. In reality, this is a notational approximation to the delocalized systems. For monocyclic conjugated molecules it is possible to determine the energy levels without doing any calcu- lations by using a graphical method. The energy levels for this type of molecules can be determined bylations by using a graphical method....
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