Theoretical study of the thermal isomerization of fulvene to benzene

✍ Scribed by L. K. Madden; A. M. Mebel; M. C. Lin; C. F. Melius

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 595 KB
• Volume: 9
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199612)9:12<801::aid-poc852>3.0.co;2-d

✦ Synopsis

The potential energy surface for the thermal isomerization of fulvene to benzene was studied by modified Gaussian-2 (G2M) and the bond additivity-corrected fourth-order perturbation Mgller-Plesset (BAC-MP4) methods. Three isomerization pathways were investigated. One involves the intermediate prefulvene by a concerted mechanism, which has a significantly higher barrier. The second, also involving prefulvene and cyclopenta-l,3-dienylcarbene intermediates, has a barrier of 84.0 kcal mol-'. The third, a multi-step pathway, includes bicyclo[3.1.0]hexa-l,3-diene and cyclohexadiene carbene intermediates. The activation energy of the multi-step pathway was calculated to be 74.3 kcalmol-', which is 7-11 kcal mol-' higher than the experimental value obtained by a brief very low-pressure pyrolysis (VLPP) study. RRKM calculations were performed on the multi-step pathway in order to determine the rate of isomerization. These theoretical results cast doubt on the validity of the VLPP data.