Document Detail


Carbon-centered radical addition and beta-scission reactions: modeling of activation energies and pre-exponential factors.
MedLine Citation:
PMID:  18175363     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A consistent set of group additive values DeltaGAV degrees for 46 groups is derived, allowing the calculation of rate coefficients for hydrocarbon radical additions and beta-scission reactions. A database of 51 rate coefficients based on CBS-QB3 calculations with corrections for hindered internal rotation was used as training set. The results of this computational method agree well with experimentally observed rate coefficients with a mean factor of deviation of 3, as benchmarked on a set of nine reactions. The temperature dependence on the resulting DeltaGAV degrees s in the broad range of 300-1300 K is limited to +/-4.5 kJ mol(-1) on activation energies and to +/-0.4 on logA (A: pre-exponential factor) for 90 % of the groups. Validation of the DeltaGAV degrees s was performed for a test set of 13 reactions. In the absence of severe steric hindrance and resonance effects in the transition state, the rate coefficients predicted by group additivity are within a factor of 3 of the CBS-QB3 ab initio rate coefficients for more than 90 % of the reactions in the test set. It can thus be expected that in most cases the GA method performs even better than standard DFT calculations for which a deviation factor of 10 is generally considered to be acceptable.
Authors:
Maarten K Sabbe; Marie-Françoise Reyniers; Veronique Van Speybroeck; Michel Waroquier; Guy B Marin
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Chemphyschem : a European journal of chemical physics and physical chemistry     Volume:  9     ISSN:  1439-7641     ISO Abbreviation:  Chemphyschem     Publication Date:  2008 Jan 
Date Detail:
Created Date:  2008-01-09     Completed Date:  2008-04-23     Revised Date:  2009-08-18    
Medline Journal Info:
Nlm Unique ID:  100954211     Medline TA:  Chemphyschem     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  124-40     Citation Subset:  IM    
Affiliation:
Laboratorium voor Chemische Technologie, Ghent University, Krijgslaan 281 S5, 9000 Gent, Belgium.
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MeSH Terms
Descriptor/Qualifier:
Carbon / chemistry*
Chemistry, Physical / methods*
Computer Simulation
Free Radicals
Kinetics
Models, Chemical
Models, Theoretical
Molecular Structure
Temperature
Thermodynamics
Chemical
Reg. No./Substance:
0/Free Radicals; 7440-44-0/Carbon
Comments/Corrections
Erratum In:
Chemphyschem. 2009 Aug 24;10(12):1951

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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