Elucidation of structure–reactivity relationships in hindered phenols via quantum chemistry and transition state theory

Quantum chemistry and transition state theory were used to study 10 different radical reactions of peroxy radicals abstracting the phenolic hydrogen of several antioxidants. The B3LYP functional with a 6-31G(d) basis set was used to characterize transition states with as many as 20 heavy atoms. The impact of quantum tunneling was investigated for a representative reaction, and it was shown that the Wigner correction provides a good approximation to more advanced semi-classical transmission coefficients. A kinetic correlation was developed that is suitable for use in kinetic modeling, allowing antioxidant chemistry to be included in large mechanistic models of hydrocarbon oxidation.