  Cyclopentadiene (CPD) is an important intermediate in the combustion of fuel
and the formation of aromatics. In the present study, the kinetics and
thermodynamic properties for hydrogen abstraction and addition with CPD, and
the related reactions including the isomerization and decomposition on the C5H7
potential energy surface were systematically investigated by theoretical
calculations. High-level ab initio calculations were adopted to obtain the
stationary points on the potential energy surfaces of CPD + H. Phenomenological
rate coefficients for temperature- and pressure-dependent reactions in the full
potential energy surface were calculated by solving the time-dependent
multiple-well RRKM/master equation, and the hydrogen abstraction reactions were
based on the conventional transition state theory. In terms of the hydrogen
abstraction reactions, the hydrogen abstraction from the saturated carbon atom
in CPD is found to be the dominant channel. For the hydrogen addition and the
associated reactions on the C5H7 PES, the allylic and vinylic cyclopentenyl
radicals and C2H2 + C3H5 were found to be the most important channels and
reactivity-promoting products, respectively. The previously neglected role of
open-chain intermediates in the evaluation of the reaction kinetics has been
suggested and the corresponding rate constants have been recommended for
inclusion in the modeling of the H+ c-C5H6 reaction. Results indicate that the
transformation from to straight-chain C5H7 is kinetically unfavorable due to
the high strain energy of the 3-membered ring structure of the isomerization
transition state. Moreover, the thermodynamic data and the calculated rate
coefficients for both H atom abstraction and addition were incorporated into
the kinetics model to examine the impact of the computed pressure-dependent
kinetics of C5H6 + H reactions on model predictions.
