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.