An ab Initio Study on [1,2] Rearrangement Reactions of Silylmethanol H3SiCH2OH

Abstract

The [1,2] rearrangement reactions of silylmethanol H 3 SiCH 2 OH were studied by ab initio calculations at the G2(MP2) levels. The reaction mechanisms were revealed through ab initio molecular orbital theory. The structuresof reactants, transition states, and products were located and fully optimized at the MP2(full)/ 6-31G(d) levels, and the G2(MP2) energies were obtained. On the basis of the MP2(full)/6-31G(d) optimized geometries, harmonic vibrational frequencies of various stationary points were calculated. The reaction paths were investigated and confirmed by intrinsic reaction coordinate calculations. The results show that the [1,2] rearrangements of silylmethanol H 3 SiCH 2 OH happen in two ways. One is via the Brook rearrangement reactions (reaction A), and the silyl group migrates from carbon atom to oxygen atom passing through a double three-membered ring transition state, forming methoxysilane. The other is that the hydroxyl group migrates from carbon atom to silicon atom, forming methylsilanol (reaction B). The barriers for the reactions A and B were computed to be 348.2 and 240.9 kJ/mol at the G2(MP2) levels, respectively. Changes (ΔS, ΔH, and AG) in thermodynamic functions, equilibrium constant K(T), and preexponential factor A(7) and reaction rate constant k(T) in Eyring transition state theory were calculated over a temperature range of 300-1300 K, and then thermodynamic and kinetic properties of the reactions were analyzed.