Benchmark ab initio mapping of the full reaction landscape of the Cl(²P_3/2) + C₂H₅OH system

A detailed exploration of the potential energy surface (PES) of the Cl(²P_3/2) + C₂H₅OH reaction is carried out using modern quantum chemical computations, extending beyond the H-abstraction pathway to include additional channels such as OH abstraction and substitution processes involving the exchange of a single atom (H) as well as entire functional groups (OH, CH₃, and CH₂OH) considering the possibility of Walden and front-side mechanisms. Beyond the reactants, all relevant stationary points are identified along the different reaction pathways, including transition states, post-reaction complexes, and the corresponding products, along with additional conformers associated with each species. The most accurate geometries are obtained at the CCSD(T)-F12b/aug-cc-pVDZ theoretical level, followed by single-point CCSD(T)-F12b/aug-cc-pVTZ and CCSD(T)-F12b/aug-cc-pVQZ energy computations. The resulting quadruple-zeta energies are refined by including five additional contributions, namely post-CCSD(T) correlation corrections (δ[T] and δ[(Q)]), core-correlation, scalar relativistic effects, and spin-orbit coupling, yielding benchmark classical energies, from which adiabatic energies are derived by incorporating zero-point energy corrections. Comparison of our theoretical adiabatic reaction enthalpies with experimental values derived from the ATcT database for ten product channels reveals outstanding agreement, demonstrating the high accuracy of the present calculations.