BOND LENGTHS AND BOND ORDERS IN BENZENOID HYDROCARBONS AND RELATED SYSTEMS - A COMPARISON OF VALENCE-BOND AND MOLECULAR-ORBITAL TREATMENTS

Bond length-bond order relationships for carbon-carbon, carbon-nitroge n and carbon-oxygen bonds in benzenoid hydrocarbons, azabenzenoids and picrate-like systems are reinvestigated and discussed. The novel rela tionships between bond lengths and bond orders, computed by valence bo nd (VB) and molecular orbital (MO) methods were established using regr ession analyses. The applicability of both methods to predict the bond lengths in conjugated systems is compared. The theoretical curves bas ed on harmonic potentials and the results of repression analyses revea l no preference for VB or MO. (C) 1998 Elsevier Science B.V.