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Academic literature on the topic 'Radical Oligomerization'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Radical Oligomerization"

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Renard, P., F. Siekmann, A. Gandolfo, J. Socorro, G. Salque, S. Ravier, E. Quivet, et al. "Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen." Atmospheric Chemistry and Physics 13, no. 13 (July 8, 2013): 6473–91. http://dx.doi.org/10.5194/acp-13-6473-2013.

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Abstract. It is now accepted that one of the important pathways of secondary organic aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the chemical mechanisms leading to macromolecules are still not well understood. It was recently shown that oligomer production by OH radical oxidation in the aerosol aqueous phase from α-dicarbonyl precursors, such as methylglyoxal and glyoxal, is irreversible and fast. Methyl vinyl ketone (MVK) was chosen in the present study as it is an α,β-unsaturated carbonyl that can undergo radical oligomerization in the aerosol aqueous phase. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under various conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series) are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights in our experiments the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the dominance of oligomerization reactions after several minutes of reaction. These processes, together with the large range of initial concentrations investigated show the fundamental role that radical oligomerization processes likely play in polluted fogs and atmospheric aerosol.
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Renard, P., F. Siekmann, A. Gandolfo, J. Socorro, G. Salque, S. Ravier, E. Quivet, et al. "Radical mechanisms of methyl vinyl ketone oligomerization through aqueous phase OH-oxidation: on the paradoxical role of dissolved molecular oxygen." Atmospheric Chemistry and Physics Discussions 13, no. 1 (January 28, 2013): 2913–54. http://dx.doi.org/10.5194/acpd-13-2913-2013.

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Abstract. It is now accepted that one of the important pathways of Secondary Organic Aerosol (SOA) formation occurs through aqueous phase chemistry in the atmosphere. However, the liquid phase chemical mechanisms leading to macromolecules are still not well understood. For α-dicarbonyl precursors, such as methylglyoxal and glyoxal, radical reactions through OH-oxidation produce oligomers, irreversibly and faster than accretion reactions. Methyl vinyl ketone (MVK) was chosen in the present study as it is an α, β-unsaturated carbonyl that can undergo such reaction pathways in the aqueous phase and forms even high molecular weight oligomers. We present here experiments on the aqueous phase OH-oxidation of MVK, performed under atmospheric relevant conditions. Using NMR and UV absorption spectroscopy, high and ultra-high resolution mass spectrometry, we show that the fast formation of oligomers up to 1800 Da is due to radical oligomerization of MVK, and 13 series of oligomers (out of a total of 26 series) are identified. The influence of atmospherically relevant parameters such as temperature, initial concentrations of MVK and dissolved oxygen are presented and discussed. In agreement with the experimental observations, we propose a chemical mechanism of OH-oxidation of MVK in the aqueous phase that proceeds via radical oligomerization of MVK on the olefin part of the molecule. This mechanism highlights the paradoxical role of dissolved O2: while it inhibits oligomerization reactions, it contributes to produce oligomerization initiator radicals, which rapidly consume O2, thus leading to the supremacy of oligomerization reactions after several minutes of reaction. These processes, together with the large ranges of initial concentrations investigated (60–656 μM of dissolved O2 and 0.2–20 mM of MVK) show the fundamental role that O2 likely plays in atmospheric organic aerosol.
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Bedilo, Alexander F., and Alexander M. Volodin. "Suppression of radical-cationic benzene oligomerization on sulfated zirconia." Reaction Kinetics and Catalysis Letters 67, no. 1 (May 1999): 197–203. http://dx.doi.org/10.1007/bf02475848.

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Bizilj, S., DP Kelly, AK Serelis, DH Solomon, and KE White. "The Self-Reactions of 1-Methoxycarbonyl-1-methylethyl and Higher Ester Radicals: Combination vs Disproportionation and Oligomeric Products from Secondary Reactions." Australian Journal of Chemistry 38, no. 11 (1985): 1657. http://dx.doi.org/10.1071/ch9851657.

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The geminate self-reactions of the title methyl, ethyl and butyl ester radicals-(2a-c), formed by decomposition of the corresponding azo precursors (1a-c) in the presence of stable nitroxide radical scavengers, were found on the basis of product analysis to comprise combination and disproportionation in the ratios 56 : 44 (methyl), 58 : 42 (ethyl) and 47 : 53 (butyl). In the absence of radical scavengers, extensive oligomerization is observed. Hydrogenation and degradation were used in conjunction with g.l.c.-m.s . to deduce the identities of the dimeric, trimeric and tetrameric products, which were in most cases subsequently confirmed by isolation and n.m.r . analysis. Of particular interest is the highly regioselective disproportionation of radical (3) to give dimethyl 4-methylpent-1-ene-2,4-dicarboxylate (8), and the further reaction of (8) with (2a) to form branched oligomers (10) and (15).
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Pithawalla, Yezdi B., Michael Meot-Ner, Junling Gao, M. Samy El Shall, Vladimir I. Baranov, and Diethard K. Bohme. "Gas-Phase Oligomerization of Propene Initiated by Benzene Radical Cation." Journal of Physical Chemistry A 105, no. 15 (April 2001): 3908–16. http://dx.doi.org/10.1021/jp003421b.

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Yurtsever, M., and E. Yurtsever. "Density functional theory study of the electrochemical oligomerization of thiophene: transition states for radical–radical and radical–neutral pathways." Polymer 45, no. 26 (December 2004): 9039–45. http://dx.doi.org/10.1016/j.polymer.2004.10.050.

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Holman, R. W., B. Atkins, Daryl Giblin, Don Rempel, and Michael L. Gross. "Cyclopropane as a propagating reagent in gas-phase radical cation oligomerization." International Journal of Mass Spectrometry 210-211 (September 2001): 569–84. http://dx.doi.org/10.1016/s1387-3806(01)00439-0.

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Renard, Pascal, Allison E. Reed Harris, Rebecca J. Rapf, Sylvain Ravier, Carine Demelas, Bruno Coulomb, Etienne Quivet, Veronica Vaida, and Anne Monod. "Aqueous Phase Oligomerization of Methyl Vinyl Ketone by Atmospheric Radical Reactions." Journal of Physical Chemistry C 118, no. 50 (October 29, 2014): 29421–30. http://dx.doi.org/10.1021/jp5065598.

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Suzuki, Takayuki, Kazuma Murakami, Naotaka Izuo, Toshiaki Kume, Akinori Akaike, Tetsu Nagata, Tomoyuki Nishizaki, et al. "E22Δ Mutation in Amyloidβ-Protein Promotesβ-Sheet Transformation, Radical Production, and Synaptotoxicity, But Not Neurotoxicity." International Journal of Alzheimer's Disease 2011 (2011): 1–8. http://dx.doi.org/10.4061/2011/431320.

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Oligomers of 40- or 42-mer amyloidβ-protein (Aβ40, Aβ42) cause cognitive decline and synaptic dysfunction in Alzheimer's disease. We proposed the importance of a turn at Glu22 and Asp23 of Aβ42 to induce its neurotoxicity through the formation of radicals. Recently, a novel deletion mutant at Glu22 (E22Δ) of Aβ42 was reported to accelerate oligomerization and synaptotoxicity. To investigate this mechanism, the effects of the E22Δ mutation in Aβ42 and Aβ40 on the transformation ofβ-sheets, radical production, and neurotoxicity were examined. Both mutants promotedβ-sheet transformation and the formation of radicals, while their neurotoxicity was negative. In contrast, E22P-Aβ42 with a turn at Glu22 and Asp23 exhibited potent neurotoxicity along with the ability to form radicals and potent synaptotoxicity. These data suggest that conformational change in E22Δ-Aβis similar to that in E22P-Aβ42 but not the same, since E22Δ-Aβ42 exhibited no cytotoxicity, unlike E22P-Aβ42 and wild-type Aβ42.
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ANDREKOPOULOS, Christopher, Hao ZHANG, Joy JOSEPH, Shasi KALIVENDI, and B. KALYANARAMAN. "Bicarbonate enhances alpha-synuclein oligomerization and nitration: intermediacy of carbonate radical anion and nitrogen dioxide radical." Biochemical Journal 378, no. 2 (March 1, 2004): 435–47. http://dx.doi.org/10.1042/bj20031466.

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α-Synuclein, a neuronal presynaptic protein, has been reported to undergo oligomerization to form toxic Lewy bodies in neurodegenerative disorders. One of the proposed mechanisms for aggregation of α-synuclein involves oxidative and nitrative modifications. In the present study, we show that addition of 3-morpholino-sydnonimine chloride (SIN-1) or slow infusion of pre-formed peroxynitrite (ONOO−) to mixtures containing α-synuclein and HCO3− markedly enhanced both nitration and aggregation of α-synuclein through dityrosine formation. Bicarbonate-dependent peroxidase activity of Cu,Zn-superoxide dismutase (SOD1) also induced covalent aggregation of α-synuclein via a CO3•−-dependent mechanism. Nitrone spin traps completely inhibited CO3•−-mediated oxidation/nitration and aggregation of α-synuclein. Conversely, α-synuclein inhibited CO3•−-induced spin adduct formation. Independent evidence for CO3•−-mediated oxidation and dimerization of α-synuclein was obtained from UV photolysis of [(NH3)5CoCO3]+, which generates authentic CO3•−. Irradiation of [(NH3)5CoCO3]+ and NO2− in the presence of α-synuclein yielded nitration and aggregation products that were similar to those obtained from a SIN-1 (or slowly infused ONOO−) and HCO3− or a myeloperoxidase/H2O2/NO2− system. Hydrophobic membranes greatly influenced α-synuclein aggregation and nitration in these systems. We conclude that both CO3•− and NO2• could play a major role in the nitration/aggregation of α-synuclein.
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Dissertations / Theses on the topic "Radical Oligomerization"

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Holmes, Bryan J. "Oligomerization of Levoglucosan in Proxies of Biomass Burning Aerosols." ScholarWorks @ UVM, 2008. http://scholarworks.uvm.edu/graddis/111.

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Biomass burning aerosols play an important role in the chemistry and physics of the atmosphere and therefore, affect global climate. Biomass burning aerosols are generally aqueous and have a strong saccharidic component due to the combustion and pyrolysis of cellulose, a major component of foliar fuel. This class of aerosol is known to affect both the absorption and scatter of solar radiation. Also, biomass burning aerosols contribute to cloud formation through their action as cloud-condensation nuclei. Many questions exist about the chemical speciation and chemical aging of biomass burning aerosols and how this affects their atmospheric properties and ultimately, global climate. Also, knowledge of the chemical components of these aerosols is important in the search for chemical tracers that can give information about the point or regional source, fuel type, and age of a biomass burning aerosol parcel. Levoglucosan was chosen for these studies as a model compound for biomass burning aerosols because of its high measured concentrations in aerosol samples. Levoglucosan often dominates the aerosol composition by mass. In this dissertation, laboratory proxy systems were developed to study the solution-phase chemistry of levoglucosan with common atmospheric reactants found in biomass burning aerosols (i.e. H+, •OH). To mimic these natural conditions, acid chemistry was studied using sulfuric acid in water (pH=4.5). The hydroxyl radical (•OH) was produced by the Fenton reaction which consists of iron, hydrogen peroxide and acid (H2SO4) in aqueous solvent. For studies in aqueous sulfuric acid, oligomers of levoglucosan were measured by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS). A rational mechanism is proposed based on both the acid-catalyzed cationic ring-opening of levoglucosan and nucleophilic attack of ROH from levoglucosan on the hemi-acetal carbon to produce pyranose oligomers through the formation of glycosidic bonds. Oligomer formation is further supported by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Reactions of levoglucosan with •OH produced from Fenton chemistry were studied in solution. Two modes of oligomerization (2000 u) were observed for reaction times between 1 and 7 days using MALDI-TOF-MS and laser desorption ionization (LDI) TOF-MS. Single-mass unit continuum mass distributions with dominant -2 u patterns were measured and superimposed by a +176/+162 u oligomer series. This latter oligomer pattern was attributed to a Criegee rearrangement (+14 u) of levoglucosan, initiated by •OH, forming a lactone (176 u). The acid-catalyzed reaction of any ROH from levoglucosan (+162 u) forms an ester through transesterification of the lactone functionality, whereupon propagation forms polyesters. Proposed products and chemical mechanisms are suggested as sources and precursors of humic-like substances (HULIS), which are known to possess a large saccharic component and are possibly formed from biomass burning aerosols. These products could also serve as secondary tracers, giving further information on the source and age of the aerosol.
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Renard, Pascal. "Photochimie et oligomérisation des composés organiques biogéniques en phase aqueuse atmosphérique." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4748.

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La pollution atmosphérique liée aux aérosols organiques secondaire (SOA) représente un des enjeux majeurs du XXIème siècle. La photochimie multiphasique des SOA constitue le coeur et l'originalité de cette thèse.Le réacteur photochimique permet de simuler en laboratoire, l'oxydation en phase aqueuse atmosphérique des composés organiques volatils biogéniques (BVOC), et notamment, la méthyl vinyl cétone (MVK), afin d'étudier la formation ces SOA.Nous étudions la réactivité de la MVK en présence de ●OH et sa capacité à oligomériser en fonction des concentrations initiales de MVK, d'oxygène, et de ●OH. Une large stratégie analytique basée sur la chromatographie liquide couplée à la spectrométrie de masse (MS) permet d'identifier des produits de réaction, et d'établir un mécanisme réactionnel, expliquant la formation des oligomères, leurs rendements et leur vieillissement.Les données colligées servent d'entrées à un modèle de boîte multiphasique, afin d'explorer la sensibilité de l'oligomérisation aux conditions atmosphériques.Ensuite, nous comparons la réactivité de la MVK en présence de ●OH à celle induite par la photolyse de l'acide pyruvique; puis nous mesurons la tension de surface engendrée par ces deux systèmes d'oligomères. Enfin, la mobilité ionique couplée à la MS permet d'observer la co-oligomérisation d'une gamme étendue de BVOC en présence de ●OH.L'oligomérisation atmosphérique implique (i) une concentration minimale de précurseurs pouvant être atteinte dans les aérosols humides via la co-oligomérisation; (ii) une réactivité en compétition avec l'oxygène dissous dans la phase aqueuse, et dont la pertinence atmosphérique reste à explorer
Air pollution caused by secondary organic aerosol (SOA) is one of the major challenges of this century. We focus this thesis on SOA , through an innovative approach, i.e. multiphase photochemistry.The photochemical reactor allows to simulate in laboratory, the atmospheric aqueous phase oxidation of biogenic volatile organic compounds (BVOC) and in particular, methyl vinyl ketone (MVK), and thus, to study SOA.We study the reactivity of MVK in the presence of ●OH and its ability to oligomerize under various initial concentrations of oxygen, MVK and ●OH. A wide analytical strategy based on liquid chromatography-mass spectrometry is used to identify the reaction products, and establish a chemical mechanism. We focus on these oligomers systems, formation, yield and aging. Collected data are used as inputs to a multiphase box model to explore the sensitivity of oligomerization to the variations of physical and chemical atmospheric parameters. The photochemistry of pyruvic acid generates radical chemistry and initiates MVK oligomerization. We closely compare this reaction to MVK ●OH oxidation. Then, we measure the surface activity of both systems. The ability of oligomers to partition to the interface could affect the climate. Finally, we used ion mobility - mass spectrometry to observe ●OH co-oligomerization of a mixture of organic compounds most representative of the atmosphere.Atmospheric oligomerization implies (i) a minimal concentration of precursors that could be reached in wet aerosol via the co-oligomerization; (ii) a reactivity in competition with the addition of the dissolved oxygen, whose the atmospheric relevance remains to be explored
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Book chapters on the topic "Radical Oligomerization"

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Schwarzenbacher, Gerald, Marion S. Gangl, Marian Goriup, Martin Winter, Matthias Grunert, Franz Renz, Wolfgang Linert, and Robert Saf. "Preparation and Radical Oligomerization of an Fe(II) Complex without Loss of Spin-Crossover Properties." In Electroactive Materials, 99–109. Vienna: Springer Vienna, 2001. http://dx.doi.org/10.1007/978-3-7091-6211-8_10.

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Slinkin, A. A., A. V. Kucherov, D. A. Kondratyev, T. N. Bondarenko, A. M. Rubinstein, and Kh M. Minachev. "Pentasil-Type Zeolites: Radical Formation, Activity in the Olefin Oligomerization and Aromatization, Processes of Coke Deposition." In Studies in Surface Science and Catalysis, 819–25. Elsevier, 1986. http://dx.doi.org/10.1016/s0167-2991(09)60952-6.

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Conference papers on the topic "Radical Oligomerization"

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Bolotov, Vasiliy Alexandrovich, Serguei Fedorovich Tikhov, Konstantin Radikovich Valeev, Vladimir Timurovich Shamirzaev, and Valentin Nikolaevich Parmon. "SELECTIVE FORMATION OF LINEAR ALPHA-OLEFINS VIA MICROWAVE CATALYTIC CRACKING OF LIQUID STRAIGHT-CHAIN ALKANES." In Ampere 2019. Valencia: Universitat Politècnica de València, 2019. http://dx.doi.org/10.4995/ampere2019.2019.9894.

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Linear even-carbon-number alpha-olefins (LAO) with four or more carbon atoms are important compounds of high demand in chemical industry as precursors of a wide range of value-added chemicals [1]. LAO are used as co-monomers for polyethylene production, for the production of alcohols (mainly in detergents and plasticizers) and for synthesis of polyalphaolefins (used in synthetic lubricants). Alpha-olefins (C4, C6, C8 and C10) are mainly used to produce poly(vinyl chloride) plasticizers, high-density and linear low-density polyethylene to impart the stress-crack resistance. C10–C14 alpha-olefins can be used to synthesize linear alkylbenzene sulfonates (synthetic detergents). A conventional route to produce alpha-olefins is oligomerization of ethylene. The process provides production of high quality alpha-olefins but is very costly. If not oligomerization, LAO can be produced by thermal cracking of waxy paraffins but the product is not pure and contains numerous internal olefins, dienes and paraffin impurities. The process is conducted in the vapor phase at relatively low cracking temperatures and needs rapid quenching to prevent side reactions such as isomerization or cyclization. In our previous work [2], we showed that the selectivity to alpha-olefins can be increased considerably via catalytic cracking of n-alkanes under selective MW heating of catalysts. In the present work, the general regularities of MW cracking of n-alkanes are presented. Porous ceramic matrix Al2O3/Al composites (ceramometals) and various carbon materials (CM) having high dielectric losses were studied as supports of the catalysts. MW cracking was conducted with n-C16H34 and n-C28H58. The influence particle size and surface morphology of ceramometals and CM on the structural and group composition of the products was studied. It was established that LAO (C2-C23) and n-alkanes (C2-C26) were the main cracking products under selective MW heating of the used supports. The quantitative analysis of the products demonstrated that the liquid-phase process is more selective to alpha-olefins at the MW catalytic cracking than at the convectional thermal cracking. Silica modification of the surface of CM was shown to suppress spark discharge (usually observed at MW heating of CM); hence, the thermal cleavage of C-C bonds on the CM surface but not in the plasma discharge contributes the most to the formation of radicals. It was shown that the selectivity to liquid alpha-olefin could be more than 85 % under MW heating of cermets in region of the E - field node and decrease considerably in the region of H - field node.
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