The Experts below are selected from a list of 108 Experts worldwide ranked by ideXlab platform
C. Mas - One of the best experts on this subject based on the ideXlab platform.
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Ionic Reactions and pyrolysis of glycerol as competing Reaction pathways in near- and supercritical water
The Journal of Supercritical Fluids, 2002Co-Authors: W. Bühler, Eckhard Dinjus, Hanns J. Ederer, Andrea Kruse, C. MasAbstract:Abstract Experimental results of the decomposition of glycerol in near- and supercritical water are presented considering measurements in the temperature range of 622–748 K, at pressures of 25, 35, or 45 MPa, Reaction times from 32 to 165 s, and different initial concentrations. The Reaction was carried out in a tubular reactor and a conversion between 0.4 and 31% was observed. The main products of the glycerol degradation are methanol, acetaldehyde, propionaldehyde, acrolein, allyl alcohol, ethanol, formaldehyde, carbon monoxide, carbon dioxide, and hydrogen. The results are compared with the studies of other working groups. The non-Arrhenius behavior of the overall degradation, as well as the pressure dependence of the Reaction rate, and furthermore, the product distribution indicates the occurrence of two competing Reaction pathways. One pathway consists of Ionic Reaction steps, which are preferred at higher pressures and/or lower temperatures. The second Reaction pathway is a free radical degradation and dominates at lower pressures and/or higher temperatures. For Reaction modeling, both mechanisms, the Ionic and the free radical Reaction network are compiled into one Reaction model. The computer software package chemkin was used for the model calculations. The Reaction model and the kinetic parameters were optimized in order to describe the experimental results for glycerol and the main products at 450 bar and all temperatures. This Reaction model, consisting of the Ionic and the free radical sub-mechanism satisfactorily describes the complex Reaction at 450 bar.
Jens Spanget-larsen - One of the best experts on this subject based on the ideXlab platform.
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Ionic Reaction products of iodine with pyridine, 4-methylpyridine, and 4-tert-butylpyridine in a polyethylene matrix. A FTIR polarization spectroscopic investigation
Chemical Physics Letters, 2019Co-Authors: Huong Thu Nguyen, Duy Duc Nguyen, Jens Spanget-larsenAbstract:Abstract The Ionic Reaction products of the title pyridines with iodine in low-density polyethylene are identified by comparison of their IR spectra with literature data. The bis(pyridine)iodine(I), bis(4-methylpyridine)iodine(I), and bis(tert-butylpyridine)iodine(I) cations are spontaneously formed in the polymer medium. At elevated temperature, the 4-methylpyridinium cation is identified as a product of the Reaction between 4-methylpyridine and iodine. In spite of their elongated molecular shape, the bis(pyridine)iodine(I) and bis(4-methylpyridine)iodine(I) cations are randomly aligned in stretched polyethylene; they probably form micro-crystalline polyiodide aggregates in the amorphous regions of the polymer. In contrast, the bis(tert-butylpyridine)iodine(I) cation is efficiently aligned in stretched polyethylene.
Marsel V. Zagidullin - One of the best experts on this subject based on the ideXlab platform.
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Gas phase synthesis of [4]-helicene.
Nature Communications, 2019Co-Authors: Long Zhao, Ralf I. Kaiser, Utuq Ablikim, Musahid Ahmed, Mikhail M. Evseev, Eugene K. Bashkirov, Valeriy N. Azyazov, Marsel V. ZagidullinAbstract:A synthetic route to racemic helicenes via a vinylacetylene mediated gas phase chemistry involving elementary Reactions with aryl radicals is presented. In contrast to traditional synthetic routes involving solution chemistry and Ionic Reaction intermediates, the gas phase synthesis involves a targeted ring annulation involving free radical intermediates. Exploiting the simplest helicene as a benchmark, we show that the gas phase Reaction of the 4-phenanthrenyl radical ([C14H9]•) with vinylacetylene (C4H4) yields [4]-helicene (C18H12) along with atomic hydrogen via a low-barrier mechanism through a resonance-stabilized free radical intermediate (C18H13). This pathway may represent a versatile mechanism to build up even more complex polycyclic aromatic hydrocarbons such as [5]- and [6]-helicene via stepwise ring annulation through bimolecular gas phase Reactions in circumstellar envelopes of carbon-rich stars, whereas secondary Reactions involving hydrogen atom assisted isomerization of thermodynamically less stable isomers of [4]-helicene might be important in combustion flames as well.
K. A. Woerpel - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Studies of the Allylic Rearrangements of α-Silyloxy Allylic Silanes to Silyloxy Vinylic Silanes
The Journal of organic chemistry, 2007Co-Authors: Angie I. Kim, Kyle L. Kimmel, Antonio Romero, Jacqueline H. Smitrovich, K. A. WoerpelAbstract:Mechanistic evidence suggests that the Lewis acid-promoted allylic rearrangement of alpha-silyloxy allylic silanes proceeds along an Ionic Reaction pathway involving a contact ion pair. The driving force for this transformation is alleviation of steric congestion at the allylic position of the alpha-silyloxy allylic silane and stabilization of pi cc by hyperconjugation.
W. Bühler - One of the best experts on this subject based on the ideXlab platform.
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Ionic Reactions and pyrolysis of glycerol as competing Reaction pathways in near- and supercritical water
The Journal of Supercritical Fluids, 2002Co-Authors: W. Bühler, Eckhard Dinjus, Hanns J. Ederer, Andrea Kruse, C. MasAbstract:Abstract Experimental results of the decomposition of glycerol in near- and supercritical water are presented considering measurements in the temperature range of 622–748 K, at pressures of 25, 35, or 45 MPa, Reaction times from 32 to 165 s, and different initial concentrations. The Reaction was carried out in a tubular reactor and a conversion between 0.4 and 31% was observed. The main products of the glycerol degradation are methanol, acetaldehyde, propionaldehyde, acrolein, allyl alcohol, ethanol, formaldehyde, carbon monoxide, carbon dioxide, and hydrogen. The results are compared with the studies of other working groups. The non-Arrhenius behavior of the overall degradation, as well as the pressure dependence of the Reaction rate, and furthermore, the product distribution indicates the occurrence of two competing Reaction pathways. One pathway consists of Ionic Reaction steps, which are preferred at higher pressures and/or lower temperatures. The second Reaction pathway is a free radical degradation and dominates at lower pressures and/or higher temperatures. For Reaction modeling, both mechanisms, the Ionic and the free radical Reaction network are compiled into one Reaction model. The computer software package chemkin was used for the model calculations. The Reaction model and the kinetic parameters were optimized in order to describe the experimental results for glycerol and the main products at 450 bar and all temperatures. This Reaction model, consisting of the Ionic and the free radical sub-mechanism satisfactorily describes the complex Reaction at 450 bar.
