Application of the AM1 and MNDO Semiempirical Quantum Mechanical Molecular Models

摘要

Studies were conducted involving the three phases of application of the Am1 and MNDO semiempirical quantum mechanical molecular models to problems in chemistry: development, testing, and use in specific investigations. As developmental work, efforts were made to obtain parameters for phosphorus valid for both trivalent and pentavalent compounds. Both the standard AM1 and MNDO algorithms, and algorithms including a core - core repulsion function modified to take into account the change in bonding interactions with change in valency, were used in these efforts. Contributory to the testing of the AM1 model, results for proton affinities and deprotonation enthalpies were extensively studied. The validity, as well as the limitations, of using AM1 in studies of reactions involving these processes were evaluated. Finally, MNDO and AM1 were used to examine two specific problems of chemical and theoretical interest, the condensation reaction of polyketide biosynthesis and the mass spectral fragmentation of cis-1-nitropropene. Results in the former study support the suggestion that a crucial factor in enzyme reactions is the exclusion of water from the reacting system. In the latter study, AM1 results were shown to correlate well with the fragmentation of the cis-1-nitropropene molecular ion.