The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Samir Zard - One of the best experts on this subject based on the ideXlab platform.
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Allylic alcohols as radical allylating agents. An overall olefination of aldehydes and ketones.
Journal of the American Chemical Society, 2008Co-Authors: Nicolas Charrier, Béatrice Quiclet-sire, Samir ZardAbstract:2-Fluoropyridyl derivatives of allylic alcohols react with xanthates in the presence of Lauroyl Peroxide to give alkenes, often with high stereoselectivity. If the allylic alcohols are themselves derived from aldehydes or ketones, the overall process becomes a synthetic equivalent of the classical Wittig and related olefination reactions.
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Synthesis of substituted 3-arylpiperidines and 3-arylpyrrolidines by radical 1,4 and 1,2-aryl migrations
Tetrahedron, 2007Co-Authors: Alexandru Gheorghe, Béatrice Quiclet-sire, Xavier Vila, Samir ZardAbstract:A route to 3-arylpiperidines and 3-arylpyrrolidines involving radical 1,4- and 1,2-aryl migrations has been explored. For the piperidines, the first route requires a xanthate addition to an N-allylarylsulfonamide, followed by acetylation and treatment with Lauroyl Peroxide to give the corresponding 1,4-aryl transfer product. This compound can be converted into the desired piperidine derivative following acidic hydrolysis. For the second approach to piperidines, addition of an α-keto xanthate to olefins of type 14 causes 1,2-aryl migration leading to an α,β-unsaturated ester, which can be converted into a piperidine by the action of ammonia or a primary amine and sodium cyanoborohydride. Substituted 3-arylpyrrolidines can be obtained by simply starting with an α-amido substituted xanthate.
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Organic Syntheses - A Xanthate‐Transfer Approach to α‐Trifluoromethylamines [2‐(N‐Acetylamino)‐4,4‐Dimethoxy‐1,1,1‐Trifluorobutane]
Organic Syntheses, 2006Co-Authors: Fabien Gagosz, Samir ZardAbstract:2,2,2-Trifluoro-1-methoxyethanol Acetamide N-(2,2,2-Trifluoro-1-hudroxyethyl)acetamide Thionyl chloride N-1-(Chloro-2,2,2-trifluoroethyl)acetamide Potassium O-ethyl xanathate S-(1-Acetylamino-2,2,2-trifluoroethyl) O-ethyl dithiocarbonate Lauroyl Peroxide Vinyl acetate 3-Acetylamino-1-ethoxythiocarbonysulfanyl-4,4,4-trifluorobutyl acetate (+/−)-10-Camphorsulfonic acid N-(3,3-Dimethoxy-1-trifluoromethyl-propyl)-acetamide Keywords: xanthate transfer; trifluoromethylamines; fluorinated derivatives; biologically active compounds; radical additions; indolines; waste disposal
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A direct approach to α-hydroxy and α-chloro trifluoromethyl derivatives
Tetrahedron Letters, 2005Co-Authors: Lucie Tournier, Samir ZardAbstract:S-1-Acyloxy-2,2,2-trifluoroethyl and S-1-chloro-2,2,2-trifluoroethyl dithiocarbonates add efficiently to various functionalised olefins to give the corresponding adducts via a radical chain reaction initiated by a small amount of Lauroyl Peroxide.
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A direct approach to a-hydroxy and a-chloro trifluoromethyl derivatives
Tetrahedron Letters, 2005Co-Authors: Lucie Tournier, Samir ZardAbstract:S-1-Acyloxy-2,2,2-trifluoroethyl and S-1-chloro-2,2,2-trifluoroethyl dithiocarbonates add efficiently to various functionalised olefins to give the corresponding adducts via a radical chain reaction initiated by a small amount of Lauroyl Peroxide. S-1-Acyloxy-2,2,2-trifluoroethyl and S-1-chloro-2,2,2- trifluoroethyl dithiocarbonates add efficiently to various functionalised olefins to give the corresponding adducts via a radical chain reaction initiated by a small amount of Lauroyl Peroxide. © 2004 Elsevier Ltd. All rights reserved.
Sheng-hung Wu - One of the best experts on this subject based on the ideXlab platform.
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thermal explosion and runaway reaction simulation of Lauroyl Peroxide by dsc tests
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Sheng-hung WuAbstract:Lauroyl Peroxide (LPO) is a typical organic Peroxide that has caused many thermal runaway reactions and explosions. Differential scanning calorimetry (DSC) was employed to determine the fundamental thermokinetic parameters that involved exothermic onset temperature (T0), heat of decomposition (ΔHd), and other safety parameters for loss prevention of runaway reactions and thermal explosions. Frequency factor (A) and activation energy (Ea) were calculated by Kissinger model, Ozawa equation, and thermal safety software (TSS) series via DSC experimental data. Liquid thermal explosion (LTE) by TSS was employed to simulate the thermal explosion development for various types of storage tank. In view of loss prevention, calorimetric application and model analysis to integrate thermal hazard development were necessary and useful for inherently safer design.
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thermal explosion and runaway reaction simulation of Lauroyl Peroxide by dsc tests
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: Sheng-hung WuAbstract:Lauroyl Peroxide (LPO) is a typical organic Peroxide that has caused many thermal runaway reactions and explosions. Differential scanning calorimetry (DSC) was employed to determine the fundamental thermokinetic parameters that involved exothermic onset temperature (T0), heat of decomposition (ΔHd), and other safety parameters for loss prevention of runaway reactions and thermal explosions. Frequency factor (A) and activation energy (Ea) were calculated by Kissinger model, Ozawa equation, and thermal safety software (TSS) series via DSC experimental data. Liquid thermal explosion (LTE) by TSS was employed to simulate the thermal explosion development for various types of storage tank. In view of loss prevention, calorimetric application and model analysis to integrate thermal hazard development were necessary and useful for inherently safer design.
Chi-min Shu - One of the best experts on this subject based on the ideXlab platform.
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Thermal stability of Lauroyl Peroxide by isoconversional kinetics evaluation and finite element analysis
Journal of The Taiwan Institute of Chemical Engineers, 2014Co-Authors: Na Zang, Xin-ming Qian, Jia-yu Liao, Chi-min ShuAbstract:Abstract Lauroyl Peroxide (LPO) is a commonly used organic Peroxide that has caused many thermal runaway reactions and explosions worldwide. Differential scanning calorimetry (DSC) was used to investigate the thermal decomposition of LPO and its exothermic onset temperature, reaction heat, and other safety parameters for prevention of runaway reactions and thermal explosions. Pre-exponential factor and apparent activation energy were determined by Friedman isoconversional method, which demonstrates that the decomposition of LPO shows a multi-step nature. The kinetic parameters and heat balance were analyzed and used for simulation of the adiabatic behavior time to maximum rate under adiabatic conditions (TMRad) and self-accelerating decomposition temperature (SADT). When the initial temperature is 32.7 °C, TMRad equals 24 h and calculated SADT of LPO is 45 °C. Application of finite element analysis (FEA) and accurate kinetic description allows determining the effect of scale, geometry, heat transfer, thermal conductivity, and ambient temperature on the heat accumulation. The reaction progress (α) and temperature distribution can be determined quantitatively at every point in time and space. This information is essential for the design of containers of LPO, cooling systems, and the measures to be taken in the event of a cooling failure.
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Evaluation of thermal hazard for Lauroyl Peroxide by VSP2 and TAM III
Journal of Thermal Analysis and Calorimetry, 2012Co-Authors: Jian-ming Wei, Mei-li You, Yung-chuan Chu, Chi-min ShuAbstract:When above certain temperature limits, Lauroyl Peroxide is an unstable material. If the thermal source cannot be properly governed during any stage in the preparation, manufacturing process, storage or transport, runaway reactions may inevitably be induced immediately. In this study, the influence of runaway reactions on its basic thermal characteristic was assessed by evaluating thermokinetic parameters, such as activation energy ( E _a) and frequency factor ( A ) by thermal activity monitor III (TAM III). This was achieved under five isothermal conditions of 50, 60, 70, 80, and 90 °C. Vent sizing package 2 (VSP2) was employed to determine the maximum pressure ( P _max), maximum temperature ( T _ma x ), maximum self-heating rate ((d T d t ^−1)_max), maximum pressure rise rate ((d P d t ^−1)_max), and isothermal time to maximum rate (( TMR )_iso) under the worst case. Results of this study will be provided to relevant plants for adopting best practices in emergency response or accident control.
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Thermal Hazard Evaluation of Lauroyl Peroxide Mixed with Nitric Acid
Molecules, 2012Co-Authors: Lung-chang Tsai, Mei-li You, Mei-fang Ding, Chi-min ShuAbstract:Many thermal runaway incidents have been caused by organic Peroxides due to the peroxy group, -O-O-, which is essentially unstable and active. Lauroyl Peroxide (LPO) is also sensitive to thermal sources and is incompatible with many materials, such as acids, bases, metals, and ions. From the thermal decomposition reaction of various concentrations of nitric acid (HNO3) (from lower to higher concentrations) with LPO, experimental data were obtained as to its exothermic onset temperature (T0), heat of decomposition (ΔHd), isothermal time to maximum rate (TMRiso), and other safety parameters exclusively for loss prevention of runaway reactions and thermal explosions. As a novel finding, LPO mixed with HNO3 can produce the detonation product of 1-nitrododecane. We used differential scanning calorimetry (DSC), thermal activity monitor III (TAM III), and gas chromatography/mass spectrometer (GC/MS) analyses of the reactivity for LPO and itself mixed with HNO3 to corroborate the decomposition reactions and reaction mechanisms in these investigations.
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Runaway reaction of Lauroyl Peroxide with nitric acid by DSC
Journal of Thermal Analysis and Calorimetry, 2010Co-Authors: Mei-li You, Jo-ming Tseng, Ming-yang Liu, Chi-min ShuAbstract:Pooling Lauroyl Peroxide (LPO) with nitric acid, we used differential scanning calorimetry (DSC) to assess the thermokinetic parameters, such as exothermic onset temperature ( T _0), heat of decomposition (Δ H _d), frequency factor ( A ), and the other safety parameters. When LPO was contaminated with nitric acid (HNO_3), we found the exploder 1-nitrododecane. Obvious products were sensitive and hazardous chemicals. Concentration reaching 1–12 N HNO_3 emitted a large amount of heat. This study combined with curve-fitting method to elucidate its unsafe characteristics and thermally sensitive structure to help prevent runaway reactions, fires and explosions in the process environment. According to the findings and the concept of inherently safer design, LPO runaway reactions could be adequately prevented in the relevant plants.
Lucian Mihut - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and optical properties of water-soluble poly(vinylpyrrolidone) - modified fullerene C_60
Polymer Bulletin, 2008Co-Authors: Edina Rusen, Bogdan Marculescu, Nicoleta Preda, Cristina Bucur, Lucian MihutAbstract:The effect of fullerene on the radical polymerization of N-vinylpyrrolidone with Lauroyl Peroxide in toluene was investigated kinetically. C_60 was found to act both as inhibitor and as retarder because the polymerization rate and the molecular weight of resulting poly(vinylpyrrolidone) is decreasing with the increase of the fullerene concentration (0-6.94 x 10^-4 mol l^-1). The water-soluble poly(vinylpyrrolidone)-modified fullerene C_60 compound was characterized by differential scanning calorimetric, Infrared and Raman spectroscopy, UV absorption and photoluminescence. Based on the results obtained by optical measurements, it is argued that by the covalent attachment of the polymeric radicals to fullerene cage the extended electronic conjugation system of the C_60 is broken leading to the appearance of a polyene structure.
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Synthesis and optical properties of water-soluble poly(vinylpyrrolidone) - modified fullerene C60
Polymer Bulletin, 2008Co-Authors: Edina Rusen, Bogdan Marculescu, Nicoleta Preda, Cristina Bucur, Lucian MihutAbstract:The effect of fullerene on the radical polymerization of N-vinylpyrrolidone with Lauroyl Peroxide in toluene was investigated kinetically. C60 was found to act both as inhibitor and as retarder because the polymerization rate and the molecular weight of resulting poly(vinylpyrrolidone) is decreasing with the increase of the fullerene concentration (0-6.94 x 10-4 mol l-1). The water-soluble poly(vinylpyrrolidone)-modified fullerene C60 compound was characterized by differential scanning calorimetric, Infrared and Raman spectroscopy, UV absorption and photoluminescence. Based on the results obtained by optical measurements, it is argued that by the covalent attachment of the polymeric radicals to fullerene cage the extended electronic conjugation system of the C60 is broken leading to the appearance of a polyene structure.
Samir Zard - One of the best experts on this subject based on the ideXlab platform.
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ß-nitro xanthates as olefin precursors
Organic Letters, 2003Co-Authors: Gilles Ouvry, Béatrice Quiclet-sire, Samir ZardAbstract:(Matrix presented) Potassium O-ethyl xanthate readily adds to a,ß-unsaturated nitro compounds to give stable ß-nitro xanthates, which undergo tin-free elimination to form olefins in good yield and good E selectivity upon simple heating with Lauroyl Peroxide in refluxing 1,2-dichloroethane.
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A direct approach to a-trifluoromethylamines
Organic Letters, 2003Co-Authors: Fabien Gagosz, Samir ZardAbstract:(Matrix presented) S-[1-(N-Acetylamino)-2,2,2-trifluoroethyl]-O-ethyl dithiocarbonate (6), a readily available xanthate, adds efficiently to various functionalized olefins to give the corresponding adducts 8 via a radical chain reaction initiated by a small amount of Lauroyl Peroxide.
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A new tin-free source of amidyl radicals
Organic Letters, 2002Co-Authors: Fabien Gagosz, Cecile Moutrille, Samir ZardAbstract:(Matrix presented) The readily available N-(O-ethyl thiocarbonylsulfanyl)amides are powerful amidyl radical precursors that undergo 5-exo cyclization to give pyrrolidinone derivatives via a radical-chain reaction initiated by a small amount of Lauroyl Peroxide.