Performance of simplified G2 model chemistry approaches in the study of unimolecular mechanisms: thermal decomposition of acetic acid in gas phase

摘要

Ab initio calculations of equilibrium structures and transition states for decarboxylation and dehydration mechanisms of gas phase pyrolysis of acetic acid are put forward. The accuracy and efficiency of different G2-based methods are compared, namely G2(MP2), G2(MP2, SVP)/B3-LYP and G2/CASSCF10-in-10 of Duan and Page. The theoretical activation energies obtained using these three methods are very close to the experimental ones and the optimized equilibrium structures at B3-LYP, MP2 and CASSCF/6-31G(d) levels are very similar. However, the computational effort is reduced for the G2 (MP2, SVP)/B3LYP calculation without any accuracy loss.