Kinetics of Intramolecular Hydrogen Atom Transfer in the Radicals >Si(O·)(R) (R = H, D, CH3, CD3, and C2H5)

Abstract

Methods are developed for obtaining oxy radicals by the photodecomposition and thermal decomposition of precursors (≡Si–O)2Si(N=N–O·)(R) and (≡Si–O)2Si(O–C·=O)(R). The mechanism of these processes is established. Kinetic data are obtained for the reaction of hydrogen atom transfer in oxy radicals (≡Si–O)2Si(O·)(R) (R = H, D, CH3, CD3, and C2H5). The activation energies of hydrogen atom transfer are found for three-, four-, and five-membered transition states: 13.5 ± 1, 18 ± 1, and <10 kcal/mol, respectively. For the reaction of H(D) atom transfer in the (≡Si–O)2Si(O·)(H(D)) radical, the kinetic isotope effect is found. Quantum-chemical calculations were used to determine the structures of transition states in the studied processes. Experimental studies were carried out using ESR spectroscopy.