Ab initio study on the mechanism of rhodium-complex-catalyzed carbonylation of methanol to acetic acid

The whole catalytic cycle of the carbonylation of methanol to acetic acid c atalyzed by Rh complex is theoretically studied. All structural geometries of reactant, intermediates, transition states and product are optimized at HF/LANL2DZ level under the ECP approximation. The potential energy profiles for elementary reactions of carbonylation are calculated respectively. The transition states are further confirmed by having one and only one imagina ry vibrational frequency. The results indicate that the activation energy, values of CH3I oxidative addition, carbonyl insertion and CH3COI reductive elimination fundamental, steps are 216.03, 128.10 and 126.55 kJ/mol, respec tively; and that the CH3I oxidative addition step is predicted to be the ra te-determining one.