Transition-state-theory calculations for reactions of O(3P) with halogenated olefins

Olleta, A. C., Lane, S. I. and Smith, S. C. (2004) Transition-state-theory calculations for reactions of O(3P) with halogenated olefins. Physical Chemistry Chemical Physics, 6 23: 5362-5369. doi:10.1039/b409689d


Author Olleta, A. C.
Lane, S. I.
Smith, S. C.
Title Transition-state-theory calculations for reactions of O(3P) with halogenated olefins
Formatted title
Transition-state-theory calculations for reactions of O(3P) with halogenated olefins
Journal name Physical Chemistry Chemical Physics   Check publisher's open access policy
ISSN 1463-9076
Publication date 2004
Sub-type Article (original research)
DOI 10.1039/b409689d
Volume 6
Issue 23
Start page 5362
End page 5369
Total pages 8
Place of publication UK
Publisher Royal Society of Chemistry
Collection year 2004
Language eng
Subject C1
250603 Reaction Kinetics and Dynamics
780103 Chemical sciences
Abstract The potential energy surfaces for the reactions of atomic oxygen in its ground electronic state, O(P-3), with the olefins: CF2=CCl2 and CF2=CF - CF3, have been characterized using ab initio molecular orbital calculations. Geometry optimization and vibrational frequency calculations were performed for reactants, transition states and products at the MP2 and QCISD levels of theory using the 6-31G(d) basis set. This database was then used to calculate the rate constants by means of Transition-State-Theory. To obtain a better reference and to test the reliability of the activation barriers we have also carried out computations using the CCSD(T)(fc)/6-311Gdagger, MP4(SDQ)(fc)/CBSB4 and MP2(fc)/CBSB3 single point energy calculations at both of the above levels of theory, as well as with the composite CBS-RAD procedure ( P. M. Mayer, C. J. Parkinson, D. M. Smith and L. Radom, J. Chem. Phys., 1998, 108, 604) and a modi. cation of this approach, called: CBS-RAD( MP2, MP2). It was found that the kinetic parameters obtained in this work particularly with the CBS-RAD ( MP2, MP2) procedure are in reasonable agreement with the experimental values. For both reactions it is found that the channels leading to the olefin double-bond addition predominates with respect to any other reaction pathway. However, on account of the different substituents in the alkenes we have located, at all levels of theory, two transition states for each reaction. Moreover, we have found that, for the reactions studied, a correlation exists between the activation energies and the electronic structure of the transition states which can explain the influence of the substituent effect on the reactivity of the halo-olefins.
Keyword Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Free-radical Polymerizations
Oxygen-atoms
Substituted Alkenes
Reaction-mechanism
Theoretical Procedures
Addition-reactions
Carbonyl Fluoride
Rate Coefficients
Ethylene
Abinitio
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 04:28:50 EST