(184r) Theoretical Study of Formic Acid Oxidation within a UV/H2O2 Advanced Oxidation Process

Designing a chemical reactor is a task that requires the evaluation of a large amount of data. Some of these, such as the kinetic constants for thermal reactions, can be estimated by theoretical calculations. These are particularly useful when dealing with unstable species or other conditions where experimental evaluation is prohibitive. However, there are a large number of methodologies that allow for the estimation of kinetic and thermodynamic parameters from first principles. In this work, semiempirical models (AM1 and PM3) were tested along with classical Hartree-Fock (HF) and Moller-Plesset perturbation (MP2) methods, and DFT functionals (B3PW91 and B3LYP) to evaluate the most suitable methodology available to describe the behavior of these oxygen-centered radical systems and to retrieve thermodynamic properties in good agreement with experimental values, where these are available.

As expected, DFT functionals performed better than the others. B3PW91/6-31++G(d,p) optimized geometries retrieved errors in bond lengths and angles of less than 0.5%, compared with microwave spectroscopy evaluated structures. For the enthalpy changes of reaction, B3LYP/6-31+G(d) estimation were 5% off of the experimental evaluation.