Molecular pathways of SOCl2 hydrolysis within mono- and diaqua complexes. A quantum chemical study

Abstract

Quantum chemistry methods (DFT, MP2, G4, and CCSD(T)) were used to calculate the energies, thermodynamic and kinetic parameters of elementary reactions of thionyl chloride (SOCl2) hydrolysis in the gas phase involving bi- and termolecular complexes. Optimization of molecular geometry and search for all the intermediates and transition states were performed at the B3LYP/6-311++G(2d,2p) and MP2/6-311++G(3df,3pd) levels. For the key stationary points, the CCSD(T)/cc-pVDZ and CCSD(T)/aug-cc-pVTZ optimizations were carried out. For both bi- and termolecular reactions, overall minimum energy reaction paths were constructed to connect all the discovered stationary points. The results show that water dimers involvement leads to a significant decrease in activation energy but not in the Gibbs free energy of activation. It was discovered that the termolecular hydrolysis of first SCl bond consists of two steps and runs through the intermediate in which the coordinated SOCl2 molecule has a flat structure.