AB-INITIO STUDY ON THE UNIMOLECULAR DECOMPOSITION MECHANISMS AND SPECTROSCOPIC PROPERTIES OF CH3OF

High-level ab initio calculations of the structure, vibrational freque ncies, and NMR spectra of the recently isolated methyl hypofluorite, C H3OF, have been carried out. When electron correlation is included in the calculations (but not at the HF level), there is a very good agree ment between the experimental and the theoretical IR and NMR spectra. Four different unimolecular decomposition pathways, all leading to CH2 O and HF were studied. Of these, two mechanisms, the synchronous singl e-step HF elimination and a two-step mechanism via the CH3O. and F-. r adicals, are predicted to be the most favorable, both having activatio n free energies of ca. 38 kcal mol(-1) at GAUSSIAN 2. A theoretical an alysis of the expected kinetic isotope effects between the competing p athways leads to a clear differentiation which can be used in experime ntal studies.