Extended Hueckel

Perhaps the first semiempirical method worth exploring is the extended Hueckel, the generalisation of the Hueckel method for systems as well. The original Hueckel method was employed to find wavefunctions and study some properties of systems. It was with the help of the extended Hueckel method that Woodward and Hoffmann determined their famous set of rules for justifying pericyclic reactions in organic chemistry (Woodward, R. B.; Hoffmann R.; Angew. Chem., 81, 797, 1969; Woodward, R. B.; Hoffmann R.; Angew. Chem. Int. Ed. Engl., 8, 781, 1969; Woodward, R. B.; Hoffmann R.; J. Am. Chem. Soc., 87(2), 395, 1965).

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