BOND-DISTORTED ORBITALS AND EFFECTS OF HYBRIDIZATION AND RESONANCE ONC-C BOND LENGTHS

A localized one-electron orbital base, called bond-distorted orbital, is introduced to study hypothetically localized structures in the fram ework of valence bond theory. The use of valence bond method with bond -distorted orbitals allows us to evaluate the effects of hybridization and resonance on carbon-carbon bond lengths at the nb initio level. V alence bond self-consistent field studies on the delocalized and hypot hetically localized structures of 1,3-butadiene and 1,3-butadiyne show that the theoretical C(sp(2))-C(sp(2)) and C(sp)-C(sp) single bond le ngths are 1.508 and 1.446 Angstrom, respectively, and that the theoret ical resonance energies of 1,3-butadiene and 1,3-butadiyne are -7.9 an d -15.8 kcal/mol, respectively.