Quantum Chemical Studies of Pyrroloquinoline Quinone: PM3 Pathways for Methanol Oxidation

By means of a PM3 characterization of the global potential energy surface, a quantum chemical study of the molecular mechanism for the oxidation of methanol by pyrroloquinoline quinone has been carried out, showing that the overall process is a stepwise mechanism. The stationary points, minima and transition state, have been located and the different energy pathways have been established. The formation of the hemiketal is controlled by simultaneous protonation of quinone oxygen and nucleophilic attack on its carbon. The assumption that the initial step is the protonation of nitrogen in the pyridine ring would appear to be false.