Theoretical study on the comparative fate of the 1-butoxy and beta-hydroxy-1-butoxy radicals

Theoretical high level ab initio BAC-MP4 and DFT calculations followed by a kinetic RRKM analysis have been performed in this work for the study of un imolecular reactions of the 1-butoxy and beta-hydroxy-1-butoxy radicals. We have shown that the substitution of H by OH on the carbon in the beta posi tion of the 1-butoxy radical (leading to the beta-hydroxy-1-butoxy radical) results in an important lowering of the decomposition barrier and a slight increase of the isomerisation barrier. Coupled to the rate constant calcul ations, this study suggests that, contrary to the fate of the 1-butoxy radi cal, the thermal decomposition is the major pathway for the beta-hydroxy-1- butoxy radical. We have also shown that, under atmospheric conditions (760 Torr and 298 K), both isomerisation and decomposition processes are still i n the fall-off range for the hydroxy radical. These behaviors have been int erpreted in terms of electronic structures and intramolecular hydrogen bond ing. This is the first theoretical study of the beta-hydroxy-1-butoxy radic al unimolecular reactions. As there are no experimental measurements on the beta-hydroxy-1-butoxy radical rate constants, this theoretical study is th e first to predict kinetic parameters for the decomposition and isomerisati on reactions of this compound.