A Theoretical Study of the Kinetics of the Hydrogen Atom Abstraction Reactions from Cyclopropane by H, O (³P), and Cl (²P₃₂) Atoms and OH Radicals

The rate constants of the H-abstraction reactions from cyclopropane by H, O (3P), Cl (P3/2), and OH radicals have been calculated over the temperature range of 250−2500 K using two different levels of theory. Calculations of optimized geometrical parameters and vibrational frequencies are performed using the MP2 method combined with the cc-pVTZ basis set and the 6–311++G(d,p) basis set. Single-point energy calculations have been carried out with the highly correlated ab initio coupled cluster method in the space of single, double, and triple (perturbatively) electron excitations CCSD(T) using either the cc-pVTZ, aug-cc-pVTZ, and aug-cc-pVQZ basis sets or the 6–311++G(3df,3pd) basis set. The CCSD(T) calculated potential energies have been extrapolated to the complete basis limit (CBS) limit. The Full Configuration Interaction (FCI) energies have been also estimated using the continued-fraction approximation as proposed by Goodson (J. Chem. Phys., 2002, 116, 6948–6956). Canonical transitionstate theory combined with an Eckart tunneling correction has been used to predict the rate constants as a function of temperature using two kinetic models (direct abstraction or complex mechanism) at two levels of theory (CCSD(T)-cf/CBS//MP2/cc-pVTZ and CCSD(T)-cf/6– 311++G(3df,3pd)//MP2/6–311++G(d,p)). The calculated kinetic parameters are in reasonable agreement with their literature counterparts for all reactions. In the light of these trends, the use of the Pople-style basis sets for studying the reactivity of other systems such as larger cycloalkanes or halogenated cycloalkanes is recommended because the 6–311++G(3df,3pd) basis set is less time consuming than the aug-cc-pVQZ basis set. Based on our calculations Correspondence to: F. Louis; e-mail: [email protected]. Supporting Information is available in the online issue at www.wileyonlinelibrary.com. C © 2015 Wiley Periodicals, Inc. KINETICS OF THE HYDROGEN ATOM ABSTRACTION REACTIONS FROM CYCLOPROPANE 233 performed at the CCSD(T)-cf/CBS//MP2/cc-pVTZ level of theory, the standard enthalpy of formation at 298 K for the cyclopropyl radical has been reassessed and its value is (290.5 ± 1.6) kJ mol−1. C © 2015 Wiley Periodicals, Inc. Int J Chem Kinet 47: 232–245, 2015