Abstract: The geometries of reactant, product and transition state for the title reaction have been optimized using density functional theory (DFT) at the B3LYP/6-31G** and B3LYP/6-311＋＋G** levels. The equilibrium states and the transition state have been verified according to the number of imaginary frequency through vibrational analysis. The intrinsic reaction coordinates (IRC) have been traced, along which the changes of energies and geometric parameters have been analyzed. The computed results indicate that the present reaction is a one-step process, with the forward and reverse energy barriers being 192 and 208 kJ•mol－1 at the level of B3LYP/6-31G**, respectively, which means that the reaction might proceed at or above room temperature.

Key words: 1-ethyl-3-methyl-imidazolium, Ionic liquid, Butene, Double bond isomerization, Transition state, Density functional theory