A COMPARATIVE-STUDY OF SEMIEMPIRICAL BOND-DISSOCIATION ENERGY CALCULATIONS

Anderson's modified version of the extended Huckel molecular orbital method and the MNDO and AMl methods of Dewar are used to study bond cleavage in molecular fragments of interest in coal liquefaction. Geometric conformations, molecular orbital coefficients for the HOMO's and LUMO's, and bond dissociation energies are computed and compared for the three methods. Qualitative agreement with experiment for bond cleavage is observed for the three methods for the neutral molecule. However the ASED-MO method appears to best describe the bond cleavage in the presence of an electron-accepting catalyst.