Kinetics of the Cyclopentadiene Decay and the Recombination of Cyclopentadienyl Radicals with H-Atoms: Enthalpy of formation of the Cyclopentadienyl Radical

摘要

The recombination of c-C_5-H_5 with H-atoms has been studied behind reflected shock waves. The obtained rate coefficients are almost independent of temperature and were found to be k_(kec)=2.6X10~(14) cm~3 mol~(-1)s~(-1) for pressures around 2 bar in the temperature range betwen 1150 and 1500 K. Together with rte coefficients for the dissociation, obtained in an earlier work (Roy et al., Proc Combust Inst 1998, 27, 329-336) at pressures and temperatures close to those applied in the present work, we calculated equilibrium constants K_c(T) for C_5H_6-><-c-C_5H_5+H.A "third law' analysis was performed. Data for the enthalpy of formation of cyclopentadienyl DH_(f,0)=65+-1 kcal mol~(-1) and DH_(f,298)=62.5+-1 kcal mol~(-1) were derived, respectively. the analysis was based upon new results on the entropy of cyclopentadienyl, recently calculated by Kiefer et a. (Phys Chem, in press). Finally, our measured data were subjected to a fall-off analysis. The simulation turned out very satisfactorily.