Wastewater decontamination methods are not sufficiently effective in the elimination of compounds derived from the pharmaceutical industry, being necessary to determine the thermodynamic and kinetic parameters in their decomposition reactions to develop more efficient methods of degradation. Through the study of the thermodynamic parameters, Enthalpy and Gibbs Free Energy using Density Functional Theory DFT, a semi-detailed degradation mechanism of acetaminophen was proposed in a OH• rich media. The results showed that the degradation starts with a nucleophilic attack of the radical OH• to the carbonyl group of acetaminophen, triggering a chain of decomposition reactions. The total degradation of the molecule requires a huge concentration of OH• radicals, a condition that is common in photoelectrocatalytic systems. The intermediate structures were characterized by DFT, and kinetic parameters such as activation energy and preexponential factors were estimated over the more relevant steps. With them, a first-order rate constant of the reaction was estimated.