ABSTRACT
Hückel theory is the first in tro d u c e d ,a n d the simplest,"^ form of the molecular orbital theory of conjugated molecules.^ Since its inception, Hückel theory has been rather successfully used, on a qualitative level, as a guide for chemists in planning and interpreting ex p erim en ts .A ttrac tiv e features of Hückel theory for experimental chemists are its simplicity and limited computational efforts. The last two decades have produced a number of results which indicate that the successful longevity of Hückel theory is based on the fact that this theory contains intrinsic information about the internal connec tivity in the conjugated systems, i.e ., it reflects the neighborhood of the atoms in conjugated s t r u c t u r e s . T h i s chapter will be concerned with the con nection between Hückel theory and the topology of the molecular ir-network.
