The pyrolysis mechanism of furan revisited

The biradical mechanisms of furan pyrolysis proposed by Lifshitz and Mackle were investigated by ab initio calculations. Critical structures of the pr oposed mechanisms were optimized by UMP2/6-31G(d,p), and energies were eval uated by the G2(MP2) method. The activation energies of the biradical chann els were predicted more than 10 kcal/mol higher than both available experim ental values acid the activation energies of a non-biradical mechanism we s tudied before. The calculated activation entropies of the biradical channel s are very close to the calculated activation entropies of the non-biradica l channels. These results indicate that the biradical mechanism is unlikely more competitive than the non-biradical mechanism. (C) 2000 Elsevier Scien ce B.V. All rights reserved.