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Modélisation moléculaire et cinétique du processus de peroxydation de composés organiques : le cas des éthers aliphatiques

Abstract : A great number of organic compounds, commonly used, could become instable if stored under poor conditions or for over-long periods in contact with air. Indeed, they can react with molecular oxygen, also at room temperature, in a process of autoxidation (peroxidation), which is self-propagating and based on free radical reactions. The products of this process are peroxidized compounds (hydroperoxide or alkyl peroxides), thermodynamically instable and well-known to be the cause of many laboratory accidents. A full characterization of such a process is very difficult at experimental level, due also to the presence of short-living radicals and many possible reaction pathways. The aim of this thesis, carried out within the RIPER (for "study of RIsk linked to the PERoxidation of chemical products") research project of INERIS, is the mechanistic study of the autoxidation of ethers, using a molecular modeling approach, in order to share some lights on the principal causes of accidental risks arising from the used of ethers, notably from storage in standard (normal) conditions. Firstly a detailed mechanistic study on diethyl ether (DEE) oxidation has been carried out, using both molecular (DFT) and kinetic modeling. The identified reaction mechanism and the developed kinetic model show that accidental risk of the process of oxidation is directly linked to the accumulation of some peroxidized compounds produced during the process (hydroperoxides in particular). The main reactions identified and characterized for the DEE oxidation process have been then studied (always at DFT level) for 13 aliphatic ethers and a common behavior in the oxidation mechanism has been found. This mechanistic generalization relieves of a detailed study of whole oxidation process for each single molecule, allowing for the energy evaluations only of the identified key steps. Finally, the inhibition mechanism of DEE oxidation has also been investigated by a DFT study considering the effect of 12 potential effective antioxidants. Preliminary results show that phenolic antioxidants are the best performing ones for the process of inhibition and, in particular, the efficacy of butylated hydroxytoluene (BHT), an additive already commonly used in DEE storage.
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Submitted on : Thursday, November 24, 2011 - 12:16:41 PM
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  • HAL Id : pastel-00644375, version 1

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Stefania Di Tommaso. Modélisation moléculaire et cinétique du processus de peroxydation de composés organiques : le cas des éthers aliphatiques. Chemo-informatique. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨pastel-00644375⟩

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