TitleThe Problematic C2H4 + F2 Reaction Barrier
Publication TypeJournal Article
Year of Publication2010
AuthorsFeng, H, Allen, WD
JournalJournal of Chemical Physics
Volume132
Pagination094304: 1–8
Date PublishedMar 7
ISBN Number0021-9606
Accession NumberISI:000275245400015
Keywordsab initio calculations, ab-initio thermochemistry, basis-set convergence, bond angles, bond lengths, correlated calculations, coupled cluster calculations, coupled-cluster theory, electron correlations, enthalpy, ethylene fluorine reaction, fluorine, heat of formation, intramolecular energy-transfer, molecular configurations, molecular electronic states, molecular fluorine, molecule-molecule reactions, organic compounds, potential energy surfaces, reaction dynamics, reaction kinetics theory, relativistic corrections, selective vibrational-excitation, shell hartree-fock, vibrational states
Abstract

The C2H4+F-2 reaction is investigated through the most rigorous electronic structure methods currently feasible, using a focal point approach to converge toward the ab initio limit. Explicit computations were executed with basis sets as large as aug-cc-pV5Z and correlation treatments as extensive as coupled cluster through full triples with a perturbative inclusion of quadruple excitations [CCSDT(Q)]. Auxiliary core correlation, diagonal Born-Oppenheimer, and first-order relativistic corrections were included. All optimized geometries and vibrational frequencies were determined completely at the CCSD(T)/aug-cc-pVQZ level. The final C2H4+F-2 reaction barrier from theory (8.0 kcal mol(-1)) is significantly higher than the recently reported experimental barrier (5.5 +/- 0.5 kcal mol(-1)). Our computations also yield a new enthalpy of formation of the fluoroethyl radical, Delta H-f(298)degrees(C2H4F)=-13.2 +/- 0.2 kcal mol(-1), whose uncertainty is an order of magnitude less than previous experimental values.

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