The pyrolysis mechanism of furan revisited

The biradical mechanisms of furan pyrolysis proposed by Lifshitz and Mackie were investigated by ab initio calculations. Critical structures of the proposed mechanisms were optimized by UMP2/6-31G(d,p), and energies were evaluated by the G2(MP2) method. The activation energies of the biradical channels were predicted more than 10 kcal/mol higher than both available experimental values and the activation energies of a non-biradical mechanism we studied before. The calculated activation entropies of the biradical channels are very close to the calculated activation entropies of the non-biradical channels. These results indicate that the biradical mechanism is unlikely more competitive than the non-biradical mechanism.