Ab Initio Investigations of the Rearrangements of some β-Haloalkoxides to Epoxides via G3 Calculations

The conformational analysis of five β-chloro- and β-bromo-alkoxides had been done. The minima and the conformational transition states were determined. The anti conformer was found to be the most stable one. Its percentage is more than 99. α-Methylation increases the nuclophilicity of oxygen .Consequently, it enhances the rate of the ring closure. In contrast to β- methylation which retards the rate of the ring closure. This observation could be attributed to the reactivity of alkyl halides in SN2 reactions. The rearrangements of g and g-conformers to carbonyl compounds are not feasible. Therefore, the main rearrangement that takes place in β- haloalkoxides is the formation of epoxides.