Theoretical studies for reaction mechanism of the gas phase elimination of 2-petnanone were carried out at B3LYP/6-31+g(d) level of theory. The mechanism for elemination is Norrish type II. The elimination reaction proceeds via a six-membered cyclic transition state with the formation of ethelene and propen-2-ol (acetone enol), which rearranges to the ketone. The calculated kinetic and thermodynamic parameters are in reasonable agreement with the reported experimental values. Analysis of the progress along the reaction coordinate, in terms of geometrical parameters suggest these reactions are dominated by the abstraction of a hydrogen atom from the g - carbon by the carbonyl oxygen to give the diradical, and together with an important cleavage of Ca-Cb bond in the transition state through concerted reaction mechanism.
