molecular modeling is growing as a research tool in chemical engineering studies, as can be seen by a simple research on the latest publications in the field. molecular investigations retrieve information on properties often accessible only by expensive and time-consuming experimental techniques, such as those involved in the study of radical-based chain reactions. in this work, different quantum chemical techniques were used to study phenol oxidation by hydroxyl radicals in advanced oxidation processes used for wastewater treatment. the results obtained by applying a dft-based model showed good agreement with experimental values available, as well as qualitative insights into the mechanism of the overall reaction chain. solvation models were also tried, but were found to be limited for this reaction system within the considered theoretical level without further parameterization.