REACTION-MECHANISM OF THE RADICAL ISOMERIZATION FROM CH3O TO CH2OH IN FROZEN METHANOL - AN AB-INITIO MO AND RRKM STUDY

The reaction mechanism of the radical isomerizations of CH3O/CH2OH in frozen methanol has been investigated by the ab initio molecular orbital method and RRKM theory. We consider two reaction channels as the conversion pathway; one is an intramolecular hydrogen rearrangement in CH3O (channel I) and the other a hydrogen abstraction from a matrix methanol molecule by CH3O (channel II). Activation energies for channels I and II are 34.8 and 14.7 kcal/mol at the MP2/6-31G* level, respectively. The RRKM calculations show that the reaction rate for channel II is significantly faster than that for channel I at low energy, whereas channel I is the dominant pathway at energies above 1.7 eV. The quantum-mechanical tunnel effect plays an important role on the rate of this isomerization reaction. Solvation effects on the reaction rate are also discussed, using a continuum model.