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Methane activation and oxidation in sulfuric acid.
MedLine Citation:
PMID:  12203359     Owner:  NLM     Status:  PubMed-not-MEDLINE    
The H/D exchange observed when methane is contacted with D(2)SO(4) at 270-330 degrees C shows that the alkane behaves as a sigma base and undergoes rapid and reversible protonation at this temperature. DFT studies of the hydrogen exchange between a monomer and a dimer of sulfuric acid and methane show that the transition states involved in the exchange are bifunctional, that is one hydrogen atom is transferred from a hydroxy group in sulfuric acid to methane, while one hydrogen atom is abstracted from methane by a non-hydroxy oxygen atom in sulfuric acid. All the transition states include a CH(5) moiety, which shows similarities to the methanium ion CH(5) (+). The calculated potential activation energy of the hydrogen exchange for the monomer is 174 kJ mol(-1), which is close to the experimental value (176 kJ mol(-1)). Solvation of the monomer and the transition state of the monomer with an extra sulfuric acid molecule, decrease the potential activation energy by 6 kJ mol(-1). The acid-base process is in competition, however, with an oxidative process involving methane and sulfuric acid which leads to CO(2), SO(2), and water, and thus to a decrease of acidity and loss of reactivity of the medium.
Alain Goeppert; Peter Dinér; Per Ahlberg; Jean Sommer
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Chemistry (Weinheim an der Bergstrasse, Germany)     Volume:  8     ISSN:  0947-6539     ISO Abbreviation:  Chemistry     Publication Date:  2002 Jul 
Date Detail:
Created Date:  2002-08-30     Completed Date:  2003-08-08     Revised Date:  2009-08-04    
Medline Journal Info:
Nlm Unique ID:  9513783     Medline TA:  Chemistry     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  3277-83     Citation Subset:  -    
Laboratoire de Physico-Chimie des Hydrocarbures, Institut de Chimie, UMR 7513, Université Louis Pasteur 4, rue Blaise Pascal, 67070 Strasbourg Cedex, France.
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