Anharmonic Effect of the Unimolecular Isomerization/Decomposition of Benzyne

Abstract

The anharmonic and harmonic rate constants were calculated for the unimolecular decomposition of o-benzyne, the isomerization of o-benzyne to m-benzyne, the isomerization of m-benzyne to p-benzyne and unimolecular decomposition of p-benzyne by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory respectively, in the canonical and microcanonical systems. The geometry and the vibrational frequencies were calculated by MP2 and B3LYPmethods with 6-311G(d,p) basis set and the barrier energies were corrected using CBS-QB3 theory. The anharmonic effect on the reactions was also examined. Comparison of results for the decompositions of benzyne indicate that both in microcanonical and canonical cases, the anharmonic effect on the decomposition of the o-C6H4 and p-C6H4 are significant, while the anharmonic effect on the two isomerizations are not pronounced.