THEORETICAL INVESTIGATION OF UNIMOLECULAR DECOMPOSITION CHANNELS OF FURAN4

Density functional theory and high-level ab initio calculations were c arried out to investigate three unimolecular decomposition channels of furan. All equilibrium and transition state structures along the prop osed decomposition channels are fully optimized by B3LYP/6-31G(*) and characterized at the same level of theory by vibrational and intrinsi c reaction coordinate analyses. Relative energies of the optimized str uctures were evaluated at theoretical levels up to QCISD(T)/6-311++G( ). The theoretical results suggest that the unimolecular decompositio n channel of isoxazole, proposed in an experimental study and implied to be the main decomposition channel of furan, is responsible only for the formation of HC drop CH and H2O double bond C double bond O, mino r products of furan thermal decomposition. A new decomposition mechani sm, proposed in the present study, is shown to be more likely responsi ble for the formation of CH3C drop CH and CO, major products of furan thermal decomposition. (C) 1998 John Wiley & Sons, Inc.