Surface versus molecular siloxy ligands in well-defined olefin metathesis catalysts: [{(RO)3SiO}Mo(=NAr)(=CHtBu)(CH2tBu)]
Surface organometallic chemistry: Similar electronic properties of molecular and surface siloxy ligands in 1 m and 1 were revealed by a structural investigation with solid-state NMR spectroscopy and a reactivity study in olefin metathesis. Despite similar initial turnover frequencies, the silica-supported catalyst 1 is more stable than 1 m and allows it to achieve higher turnovers, thus showing the advantage of site isolation on surfaces. (Figure Presented)
Blanc, Frederic,Coperet, Christophe,Thivolle-Cazat, Jean,Basset, Jean-Marie,Lesage, Anne,Emsley, Lyndon,Sinha, Amritanshu,Schrock, Richard R.
p. 1216 - 1220
(2007/10/03)
Etudes des reactions d'oxydation du n-heptane et de l'isooctane
The oxidation mechanisms of two alkanes that have quite different octane numbers: n-heptane (0) and isooctane (100), were investigated to obtain a better understanding of the chemical mechanism of autoignition phenomena and to improve the compatibility of the available fuels with the engines.The experimental study was performed at 923 K in a setup equipped with a jet-stirred reactor.The oxidation mechanisms of n-heptane and isooctane were simplified first by a purely kinetic analysis based on the product formation and then by using a software of simulation of reaction mechanisms.The very different behaviour of these two hydrocarbons was explained by the presence, in the products of isooctane oxidation, of alkenes, which would have an antiknock effect due to the formation of resonance-stabilized radicals. - Keywords: oxidation reaction; n-heptane; isooctane; autoignition; modelling
Simon, Yves,Scacchi, Gerard,Baronnet, Francois
p. 1391 - 1402
(2007/10/03)
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