Substituent effect on the hydrolysis of chlorosilanes: quantum chemical and QSPR study

Abstract

The substituent effect on the hydrolysis of chlorosilanes was studied computationally. Sixteen practically important compounds with SiCl bond were considered, and the stationary points along their reaction pathway with different-sized water clusters (monomer and tetramer) were investigated using density functional theory. While in the case of a single reactant water molecule the reactions are endothermic for most of the substituents, with the larger reactant water cluster the reactions are mainly exothermic. In the case of the reactant cluster consisting of four water molecules both an inversion and a retention pathway are located. The reaction barrier for both pathways is about 50% that with a single water molecule, and the inversion pathway is somewhat more preferred over retention for most substituents except for cage-like chlorosilanes. Strong correlations were indentified between several factors of substituted chlorosilanes and their activation energy of hydrolysis. Cl-Si-O bond angle in the transition state as an indirect descriptor of steric effect, electrophilicity and partial charge at silicon of the reactant chlorosilane, and the opportunity of extra H-bond formation have influence on the reaction barrier. Quantitative structure-property relationship (QSPR) analysis showed that the hydrolysis activation energy can be well described by using these factors.