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Articles de revues sur le sujet « High-yield reaction »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 10 mars 2023

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1

HART, PETER W. « Enhancing yield through high-kappa pulping ». October 2014 13, no 10 (1 novembre 2014) : 33–35. http://dx.doi.org/10.32964/tj13.10.33.

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Chemical pulping consists of a collection of delignification reactions designed to remove amorphous lignin from the fiber matrix while preserving carbohydrates in a fibrous form. Commercially available cooking processes are relatively nonselective with reagents attaching both lignin and carbohydrates. Generally, the carbohydrates react more slowly than the lignin, so some carbohydrate selectivity does exist for modern pulping processes. However, extended reaction times or excessive reaction temperatures will substantially reduce pulp yield. To date, only a few methods of converting high-kappa pulp into enhanced fiber yield have been demonstrated.
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2

Wang, Qi, Guo Zheng, Jian Jie Ai et Xue Jing Wei. « The Synthesis of High Yield Diglycerin Borate ». Applied Mechanics and Materials 55-57 (mai 2011) : 312–16. http://dx.doi.org/10.4028/www.scientific.net/amm.55-57.312.

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High yield diglycerin borate(DGB) have been synthesized by the raw materials glycerol and boric acid in this paper. The structure of the products was characterized by FTIR and11B NMR. The yield of the products was discussed by reaction conditions that were material ratio, reaction temperature, reaction pressure etc. and then the optimum process conditions of preparing DGB was decided. In this condition, high yield DGB can be prepared which could reach more than 96%.
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Jin, Shuai Yong, Kang Kang Guo, Hui Min Qi, Ya Ping Zhu et Fan Wang. « High Yield Polyborosilazane Precursor for SiBN Ceramics ». Advanced Materials Research 1004-1005 (août 2014) : 409–14. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.409.

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The processible and high yield polyborosilazane (PBSZ) precursor for SiBN ceramics was prepared by coammonolysis reaction of dichlorosilane and trichloroborazine. The synthesized PBSZ precursor was characterized by Fourier Transform Infrared spectroscopy (FTIR),1H,11B, and29Si Nuclear Magnetic Resonance (NMR), and its ceramic conversion chemistry was investigated by differential scanning calorimetric (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). The PBSZ precursor is a viscous liquid and changes to an insoluble solid via a cross-linking reaction between the N-H group and Si-H group as post-heated from 60 to 180°C. The insoluble solid is transformed to Si3N4and BN amorphous structures with an approximately 95% ceramic yield after being pyrolyzed to 1000°C.
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Daum, B., et K. Buchholz. « High Yield and High Selectivity of Reactions in the Frozen State--the Acceptor Reaction of Dextransucrase ». Biocatalysis and Biotransformation 20, no 1 (janvier 2002) : 15–21. http://dx.doi.org/10.1080/10242420210156.

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Chuliá-Jordán, Raquel, David Santamaría-Pérez, Tomás Marqueño, Javier Ruiz-Fuertes et Dominik Daisenberger. « Oxidation of High Yield Strength Metals Tungsten and Rhenium in High-Pressure High-Temperature Experiments of Carbon Dioxide and Carbonates ». Crystals 9, no 12 (17 décembre 2019) : 676. http://dx.doi.org/10.3390/cryst9120676.

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The laser-heating diamond-anvil cell technique enables direct investigations of materials under high pressures and temperatures, usually confining the samples with high yield strength W and Re gaskets. This work presents experimental data that evidences the chemical reactivity between these refractory metals and CO2 or carbonates at temperatures above 1300 °Ϲ and pressures above 6 GPa. Metal oxides and diamond are identified as reaction products. Recommendations to minimize non-desired chemical reactions in high-pressure high-temperature experiments are given.
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6

Wolfe, David R. « Investor reaction to new issuances of U.S. high-yield debt ». Corporate Ownership and Control 5, no 3 (2008) : 358–84. http://dx.doi.org/10.22495/cocv5i3c3p4.

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This paper investigates firms issuing high-yield debt and the impact on their stock price by identifying determinants of the negative abnormal return that surrounds the announcement of an issue in the short-run. It is learned the length, coupon payment and amount of the issue are significant in explaining the CAR as is the age of the firm, first-time issuers and the marketplace where its stock trades. Firm performance ratios including the current and total-asset-turnover ratio also have explanatory power. These determinants of the CAR have an explanatory power approaching 55%
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7

Duangwang, S., et C. Sangwichien. « Optimization Studies on Acid Hydrolysis of Pretreated Oil Palm Empty Fruit Bunch for Production of Xylose by Application of Response Surface Methodology ». Advanced Materials Research 699 (mai 2013) : 77–82. http://dx.doi.org/10.4028/www.scientific.net/amr.699.77.

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Oil palm empty fruit bunch is a lignocellulosic material from palm oil plantations. It is a potential source of xylose which can be used as a raw material for production of xylitol. Using of lignocellulosic waste for bioconversion to fuels and chemicals is justifiable as these materials are low cost, renewable and widespread sources of sugars. The objective of the present study was to determine the effect of H2SO4 concentration, reaction temperature and reaction time for acid hydrolysis of pretreated OPEFB, pretreated OPEFB with reaction temperature, reaction time and NaOH concentration were 130 °C, 40 min and 15% (w/v), respectively to achieve high xylose yield. Batch reactions were carried out under various reaction temperature, reaction time and H2SO4 concentration. Response Surface Methodology (RSM) was followed to optimize acid hydrolysis in order to obtain high yield of xylose. The optimum reaction temperature, reaction time and H2SO4 concentration were found to be 140 °C, 90 min and 7% (w/v), respectively. The maximum value of xylose was obtained 56.39 g/l by using the above condition. The best result of xylose yield obtained was 126%.
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8

Kobayashi, Toshiaki, et Keith H. Pannell. « A general, high-yield reaction for the formation of (chloromethyl)oligosilanes ». Organometallics 9, no 8 (août 1990) : 2201–3. http://dx.doi.org/10.1021/om00158a012.

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Mat Radzi, Salina, Nurul Jannah Abd Rahman, Hanina Mohd Noor et Mahiran Basri. « High Yield Synthesis of Kojic Ester Using Dual Enzymes System and their Antibacterial Activity ». Key Engineering Materials 594-595 (décembre 2013) : 362–69. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.362.

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Enzymatic synthesis of kojic ester, a bio-based whitening agent, was successfully carried out via esterification reaction between oleic acid and kojic acid. Commercial immobilized lipases of Novozym 435 and Lipozyme RM IM were used in combination as biocatalyst in the reaction system. Various reaction parameters were chosen to optimize the reaction in order to obtain a high yield of kojic ester including the best ratio of lipases, reaction time and reaction temperature. The optimum conditions for the synthesis of kojic ester was achieved at reaction time of 12 hours, temperature of 60 οC and equal ratio of lipases to produce more than 70 % yield. Antimicrobial tests of synthesized kojic ester towards several types of bacteria via Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) analyses were also examined. The results obtained suggested that kojic ester exhibits a good bactericidal effect towards all bacteria tested such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium.
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10

Fakeeha, Anis, Ahmed A. Ibrahim, Hesham Aljuraywi, Yazeed Alqahtani, Ahmad Alkhodair, Suliman Alswaidan, Ahmed E. Abasaeed, Samsudeen O. Kasim, Sofiu Mahmud et Ahmed S. Al-Fatesh. « Hydrogen Production by Partial Oxidation Reforming of Methane over Ni Catalysts Supported on High and Low Surface Area Alumina and Zirconia ». Processes 8, no 5 (25 avril 2020) : 499. http://dx.doi.org/10.3390/pr8050499.

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The catalytic activity of the partial oxidation reforming reaction for hydrogen production over 10% Ni supported on high and low surface area alumina and zirconia was investigated. The reforming reactions, under atmospheric pressure, were performed with a feed molar ratio of CH4/O2 = 2.0. The reaction temperature was set to 450–650 °C. The catalytic activity, stability, and carbon formation were determined via TGA, TPO, Raman, and H2 yield. The catalysts were calcined at 600 and 800 °C. The catalysts were prepared via the wet-impregnation method. Various characterizations were conducted using BET, XRD, TPR, TGA, TPD, TPO, and Raman. The highest methane conversion (90%) and hydrogen yield (72%) were obtained at a 650 °C reaction temperature using Ni-Al-H-600, which also showed the highest stability for the ranges of the reaction temperatures investigated. Indeed, the time-on-stream for 7 h of the Ni-Al-H-600 catalyst displayed high activity and a stable profile when the reaction temperature was set to 650 °C.
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11

Raducanu, Cristian Eugen, Adina Ionuta Gavrila, Tanase Dobre et Petre Chipurici. « Study on Alumina Supported Heterogeneous Catalysts for Biodiesel Production ». Revista de Chimie 69, no 8 (15 septembre 2018) : 2138–43. http://dx.doi.org/10.37358/rc.18.8.6488.

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In this work four heterogeneous catalysts were studied first by preparing a gama-alumina catalytic support then by impregnating with acidic and base compounds to gain certain properties needed to catalyze vegetable oils conversion to biodiesel. The resulted new catalytic properties allowed us to simultaneously conduct esterification and transesterification reaction in a single step when waste cooking oils with a high free fatty acid content were converted to biodiesel. The prepared catalysts were thermally and chemically stable and exhibited good catalytic activity when tested in (trans)esterification reactions to yield biodiesel. The effects of catalyst loading, methanol/oil molar ratio and reaction time on biodiesel yield along with catalyst reusability were investigated. The highest biodiesel yield reached was 88.10% at 65oC reaction temperature, 15:1 methanol/oil molar ratio, 5% catalyst loading and 4 h reaction time.
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12

Obregón-Mendoza, Marco A., William Meza-Morales, Yair Alvarez-Ricardo, M. Mirian Estévez-Carmona et Raúl G. Enríquez. « High Yield Synthesis of Curcumin and Symmetric Curcuminoids : A “Click” and “Unclick” Chemistry Approach ». Molecules 28, no 1 (30 décembre 2022) : 289. http://dx.doi.org/10.3390/molecules28010289.

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The worldwide known and employed spice of Asian origin, turmeric, receives significant attention due to its numerous purported medicinal properties. Herein, we report an optimized synthesis of curcumin and symmetric curcuminoids of aromatic (bisdemethoxycurcumin) and heterocyclic type, with yields going from good to excellent using the cyclic difluoro-boronate derivative of acetylacetone prepared by reaction of 2,4-pentanedione with boron trifluoride in THF (ca. 95%). The subsequent cleavage of the BF2 group is of significant importance for achieving a high overall yield in this two-step procedure. Such cleavage occurs by treatment with hydrated alumina (Al2O3) or silica (SiO2) oxides, thus allowing the target heptanoids obtained in high yields as an amorphous powder to be filtered off directly from the reaction media. Furthermore, crystallization instead of chromatographic procedures provides a straightforward purification step. The ease and efficiency with which the present methodology can be applied to synthesizing the title compounds earns the terms “click” and “unclick” applied to describe particularly straightforward, efficient reactions. Furthermore, the methodology offers a simple, versatile, fast, and economical synthetic alternative for the obtention of curcumin (85% yield), bis-demethoxycurcumin (78% yield), and the symmetrical heterocyclic curcuminoids (80–92% yield), in pure form and excellent yields.
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13

Liu, Michael T. H., Yuri N. Romashin et T. K. Venkatachalam. « Photolysis of 3-chloro-3-aryldiazirines in the presence of amines and allyl alcohol ». Canadian Journal of Chemistry 72, no 9 (1 septembre 1994) : 1961–65. http://dx.doi.org/10.1139/v94-250.

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When photolysis of arylchlorodiazirines is performed in the presence of either alkyl- or allyl-substituted amines, either N-alkyl- or N-allyl-substituted amines result as the sole high-yield (64-93%) products. Photolysis in the presence of phenylallylamine produces a rearranged product in poor yield (11–15%) whereas the reaction of allyl alcohol with arylchlorocarbene gives exclusively diallyl acetals in high yield (70%). The rate constants for these reactions were obtained by laser flash photolysis. Allyl phenyl ether forms a cyclopropanated product when treated with arylchlorocarbene. The different behaviour of these compounds may be attributed to the nucleophilicity at the nitrogen and oxygen centres of these compounds, when the latter are subjected to the substitutions described above. The formation of a cyclopropanated product when allyl phenyl ether is used differs from the reaction of bis (methoxycarbonyl) carbene with allyl ethers, as reported in the literature. The formation of this cyclopropanated product demonstrates the absence of an oxonium ylide intermediate during the reaction.
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14

Huang, Yao-Bing, Tao Yang, Yu-Ting Lin, Ying-Zhi Zhu, Li-Cheng Li et Hui Pan. « Facile and high-yield synthesis of methyl levulinate from cellulose ». Green Chemistry 20, no 6 (2018) : 1323–34. http://dx.doi.org/10.1039/c7gc02883k.

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The production of alkyl levulinates from cellulose was successfully achieved by using a simple and efficient metal salt catalyst, Al2(SO4)3, offering a high yield up to 70.6% under microwave conditions within a short reaction time of 40 minutes.
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15

Vasilevich, S. V., M. V. Malko, D. V. Degterov et A. N. Asadchyi. « Computational Study of the Yield of Solid Wood Pyrolysis Products under High Pressure ». ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 63, no 3 (28 mai 2020) : 253–63. http://dx.doi.org/10.21122/1029-7448-2020-63-3-253-263.

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The kinetic model of wood pyrolysis under pressure is discussed in the present paper taking into account the diffusion of the resulting gas-phase products (i.e. heavy hydrocarbons) and their decomposition reactions. This model is based on a simplified mechanism of wood pyrolysis, including two parallel chemical reactions, viz. the primary decomposition reaction of wood biomass with the formation of solid and gaseous components and the thermal decomposition reaction in the biomass pores of hydrocarbons formed in the primary process. The model takes into account the diffusion processes of the primary pyrolysis products from the resulting pores and thermal decomposition in the pores of these products. Based on the developed model, a computer program for calculating the main parameters of the pyrolysis process under pressure was created and the mass yield of solid pyrolysis products under various conditions was calculated. The calculation took into account the main parameters that affect the yield of solid wood biomass products, viz. temperature and pyrolysis pressure, particle sizes, porosity, etc. The calculations demonstrated that the increase of the pressure at which the pyrolysis of wood biomass is carried out causes an increase of the formation of the amount of solid products, which corresponds to the available experimental data. It was established that at a pressure of 1 atm when a sample size is of 0.025 m, the maximum yield of solid products is observed at the temperature of 600 °C. As the pressure increases the maximum yield increases, while the temperature at which the maximum is reached decreases. So, at a pressure of 10 atm when a particle size is of 0.025 m, the maximum yield of solid products is observed at the temperature of about 500 °C, and it is higher than that at 1 atm by 1.18 times. It was also determined that the temperature of the maximum yield of charcoal decreases with increasing sizes of pyrolyzable samples. Thus, when a sample size is of 0.5 m, this temperature is about 400 °C at 10 atm.
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16

Sun, Chivin, Joseph S. Gardner, Endrit Shurdha, Kelsey R. Margulieux, Richard D. Westover, Lisa Lau, Gary Long et al. « A High-Yield Synthesis of Chalcopyrite CuInS2Nanoparticles with Exceptional Size Control ». Journal of Nanomaterials 2009 (2009) : 1–7. http://dx.doi.org/10.1155/2009/748567.

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We report high-yield and efficient size-controlled syntheses of Chalcopyrite CuInS2nanoparticles by decomposing molecular single source precursors (SSPs) via microwave irradiation in the presence of 1,2-ethanedithiol at reaction temperatures as low as 100°C and times as short as 30 minutes. The nanoparticles sizes were 1.8 nm to 10.8 nm as reaction temperatures were varied from 100°C to 200°C with the bandgaps from 2.71 eV to 1.28 eV with good size control and high yields (64%–95%). The resulting nanoparticles were analyzed by XRD, UV-Vis, ICP-OES, XPS, SEM, EDS, and HRTEM. Titration studies by1H NMR using SSP1with 1,2-ethanedithiol and benzyl mercaptan were conducted to elucidate the formation of Chalcopyrite CuInS2nanoparticles.
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Shahi, Akbar Massoumi, Mohammad Nikpassand et Leila Zare Fekri. « Acidic Ionic Liquid-catalyzed Synthesis of Pyrano[4,3-b]pyran-5(4H)-ones using 4,4,4-trifluoro-1-phenylbutane-1,3-dione as a Building Block ». Current Organic Synthesis 17, no 8 (28 octobre 2020) : 648–53. http://dx.doi.org/10.2174/1570179417666200520111536.

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Aims: synthesis of pyrano[c-2,3]chromens with Ionic Liquid catalyst with simple method. Background: Synthesis of pyrano[c]coumarins has a special place in the structure due to two bioactive compounds in its structure and attracts a great deal of attention in this research work, it has been attempted to attach chromatically valuable skeletons to them and synthesize the pyrano [c] coumarines, which can potentially have high biological properties. For this purpose, electrophilic β-ketoester ringing in the presence of ionic liquid catalysts was used. While optimizing the catalyst recovery, it is possible to synthesize several coumarine pyrano[ c]derivatives with high yield. Objective: This paper describes an efficient procedure for the multi-component reaction of aromatic aldehydes, 4,4,4-Trifluoro-1-phenyl-1,3-butanedione and 4-hydroxycoumarinwhich catalyzed by Ioniq liquid (OlmDSA), at room temperature. This catalyst was synthesized with new simple procedure. This protocol has advantages of simplicity, mild condition and high yield. Materials and Methods: After formation of a new stain corresponding to the alkene intermediate, 4-hydroxy coumarin (1 mM) was added. The reaction was progressed by thin layer chromatography in a 1: 2 ratio solvent containing ethyl acetate and hexane. The reaction mixture was then stirred for one hour. After the reaction was complete, the catalyst was first removed by washing. Ethanol was then added to the reaction residue and washed and finally filtered. The residual solid on the filter paper after drying was considered as the product and was taken to confirm. its structure, melting point and spectra. The following is a general overview of the reaction. Results and Discussion: In addition to the advantages mentioned for this tri-component reaction, the conservation of the coumarin ring is very important in this research design because it is formed in many of the reported open reactions and phenolic ring. Conclusion: The benefits of this work include simple reaction steps, review of reaction progress by TLC chromatography, simple separation of the catalyst by washing and reuse for three times without any reduction in yield and high reaction yield.
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Ji, Zhe, Ji Chen, Liang Huang et Gaoquan Shi. « High-yield production of highly conductive graphene via reversible covalent chemistry ». Chemical Communications 51, no 14 (2015) : 2806–9. http://dx.doi.org/10.1039/c4cc09144b.

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19

Lacina, Michael, et Zhaohui Zhang. « Dividend Initiations by High-Tech Firms ». Review of Pacific Basin Financial Markets and Policies 11, no 02 (juin 2008) : 201–26. http://dx.doi.org/10.1142/s0219091508001325.

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We study the stock price and trading volume reactions to dividend initiations by high-tech firms relative to those by non-high tech firms. We find significant positive cumulative abnormal returns and abnormal trading volume for both high-tech and non-high tech firms surrounding dividend initiations. However, when we control for variables such as size and dividend yield, stock returns and trading volume around dividend initiations are higher for high-tech firms than for non-high tech firms. We also find evidence that stock returns and trading volume for high-tech firms are higher with increases in liquid assets, although the volume reaction to increases in liquid assets is stronger than the return reaction, perhaps indicating clientele shifts. Overall, our findings convey stronger investor reaction to dividend initiations by high-tech firms, especially those with sufficient liquid assets.
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20

Zhou, Xiao-Yu, Xia Chen et Liang-Guang Wang. « Recycled Pd/C-Catalyzed Heck Reaction of 2-Iodoanilines under Ligand-Free Conditions ». Synthesis 49, no 24 (28 août 2017) : 5364–70. http://dx.doi.org/10.1055/s-0036-1590895.

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Recyclable Pd/C-catalyzed Heck reaction of 2-iodoanilines with acrylate has been developed. The reaction occurred readily in 1,4-dioxane using Pd/C (10 wt%) as catalyst under ligand-free conditions, and the cross-coupling products were obtained with medium to high yield. Gram-scale reactions and recycling of the catalyst were also demonstrated.
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21

Saporito, Dafne, Sergio A. Rodriguez et Maria T. Baumgartner. « Visible Light-Promoted C–C Bond Formation from Hydroxyaryls in Water ». Australian Journal of Chemistry 72, no 12 (2019) : 978. http://dx.doi.org/10.1071/ch19378.

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An eco-friendly and direct arylation of hydroxyaryls in water using photoinduced reactions with different substrates (1-bromo-2-naphthol, 1-iodo-2-naphthol, N-(2-iodophenyl)acetamide, 5-bromouracil, 2-iodo-N-methylbenzamide, and 2-iodobenzamide) was studied. For example, π-expanded coumarins, compounds with potential optical applications, were synthesized in very high yield, without the use of toxic reagents, in a one-pot reaction. In addition, we demonstrate that the irradiation source (halogen lamp) can be efficiently replaced by an LED without altering the reaction yield.
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22

Bang, Hyun Bae, Su Young Han, Da Hye Choi, Jung Woon Hwang et Jong-Gab Jun. « High yield total syntheses of XH-14 derivatives using Sonogashira coupling reaction ». Arkivoc 2009, no 2 (11 février 2009) : 112–25. http://dx.doi.org/10.3998/ark.5550190.0010.212.

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23

Griffith, Julie A., David J. McCauley, Richard E. Barrans et Albert W. Herlinger. « High Yield Synthesis of Tetraethyl Alkylene-Diphosphonates via the Michaelis-Arbuzov Reaction ». Synthetic Communications 28, no 23 (décembre 1998) : 4317–23. http://dx.doi.org/10.1080/00397919808004465.

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Bradshaw, Jerald S., Krzysztof E. Krakowiak, Reed M. Izatt et Daria J. Zamecka-Krakowiak. « New high yield syntheses of cyclams using the crab-like cyclization reaction ». Tetrahedron Letters 31, no 8 (janvier 1990) : 1077–80. http://dx.doi.org/10.1016/s0040-4039(00)88730-4.

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Panfilova, E. V., B. N. Khlebtsov, A. M. Burov et N. G. Khlebtsov. « Study of polyol synthesis reaction parameters controlling high yield of silver nanocubes ». Colloid Journal 74, no 1 (février 2012) : 99–109. http://dx.doi.org/10.1134/s1061933x11060147.

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26

Volk, M., G. Scheidel, A. Ogrodnik, R. Feick et M. E. Michel-Beyerle. « High quantum yield of charge separation in reaction centers of Chloroflexus aurantiacus ». Biochimica et Biophysica Acta (BBA) - Bioenergetics 1058, no 2 (juin 1991) : 217–24. http://dx.doi.org/10.1016/s0005-2728(05)80240-3.

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Chronopoulos, Demetrios D., Aristides Bakandritsos, Petr Lazar, Martin Pykal, Klára Čépe, Radek Zbořil et Michal Otyepka. « High-Yield Alkylation and Arylation of Graphene via Grignard Reaction with Fluorographene ». Chemistry of Materials 29, no 3 (31 janvier 2017) : 926–30. http://dx.doi.org/10.1021/acs.chemmater.6b05040.

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28

Hassanzadeh, Salman, Nina Aminlashgari et Minna Hakkarainen. « Chemo-selective high yield microwave assisted reaction turns cellulose to green chemicals ». Carbohydrate Polymers 112 (novembre 2014) : 448–57. http://dx.doi.org/10.1016/j.carbpol.2014.06.011.

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29

Betou, Marie, Nicolas Kerisit, Esme Meledje, Yann R. Leroux, Claudine Katan, Jean-François Halet, Jean-Claude Guillemin et Yann Trolez. « High-Yield Formation of Substituted Tetracyanobutadienes from Reaction of Ynamides with Tetracyanoethylene ». Chemistry - A European Journal 20, no 31 (24 juin 2014) : 9553–57. http://dx.doi.org/10.1002/chem.201402653.

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Liu, Qian, Chia-Wei Hsu, Trevor L. Dzwiniel, Krzysztof Z. Pupek et Zhengcheng Zhang. « A fluorine-substituted pyrrolidinium-based ionic liquid for high-voltage Li-ion batteries ». Chemical Communications 56, no 53 (2020) : 7317–20. http://dx.doi.org/10.1039/d0cc02184a.

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Fluorinated pyrrolidinium bis(fluorosulfonyl)imides were successfully synthesized using a facile one-step reaction by reacting fluorinated pyrrolidine with CH3FSI with high purity and yield. The new IL shows good performance in Li-ion batteries.
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Chow, Toby Wai-Shan, Guo-Qiang Chen, Yungen Liu, Cong-Ying Zhou et Chi-Ming Che. « Practical iron-catalyzed atom/group transfer and insertion reactions ». Pure and Applied Chemistry 84, no 8 (2 mai 2012) : 1685–704. http://dx.doi.org/10.1351/pac-con-11-11-08.

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Iron-catalyzed reactions are receiving a surge of interest owing to the natural abundance and biocompatibility of Fe and the urge to develop practically useful sustainable catalysis for fine chemical industries. This article is a brief account of our studies on the C–O and C–N bond formation reactions catalyzed by Fe complexes supported by oligopyridine, macrocyclic tetraaza, and fluorinated porphyrin ligands. The working principle is the in situ generation of reactive Fe=O and Fe=NR intermediates supported by these oxidatively robust N-donor ligands for oxygen atom/nitrogen group transfer and insertion reactions. The catalytic reactions include C–H bond oxidation of saturated hydrocarbons (up to 87 % yield), epoxidation of alkenes (up to 96 % yield), cis-dihydroxylation of alkenes (up to 99 % yield), epoxidation–isomerization (E–I) reaction of aryl alkenes (up to 94 % yield), amination of C–H bonds (up to 95 % yield), aziridination of alkenes (up to 95 % yield), sulfimidation of sulfides (up to 96 % yield), and amide formation from aldehydes (up to 89 % yield). Many of these catalytic reactions feature high regio- and diastereoselectivity and/or high product yields and substrate conversions, and recyclability of the catalyst, demonstrating the applicability of Fe-catalyzed oxidative organic transformation reactions in practical organic synthesis.
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32

Habibi, Azizollah, Sahar Khosravi, Seyyed M. Shahcheragh et Mohd B. Abdul Rahman. « One-Pot Green Synthesis of Some Novel N-Substituted 5-Amino-1,3,4- Thiadiazole Derivatives ». Letters in Organic Chemistry 17, no 7 (7 juillet 2020) : 517–22. http://dx.doi.org/10.2174/1570178616666190926105533.

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In the current study, a green, one-pot, three-component reaction was performed to prepare novel N-substituted 5-amino-1,3,4-thiadiazole derivatives. The thiadiazoles were obtained from the reaction of a ketene S,S-acetal of Meldrum’s acid or barbituric acid (as key intermediates), hydrazine, and isothiocyanate. The key advantages of this manner include environmentally safe reactions, high yield, appropriate reaction time, simple reaction conditions, and use of a green reaction solvent. The structure of thiadiazoles was determined based on the spectroscopic data.
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33

Jalil, Mohd Jumain, Kamariah Noor Ismail, Abdul Rani Hidayu, Mohamad Hasni Hassan, Intan Suhada Azmi, Aliff Farhan Bin Mohd Yamin et Khairul Azhar Kamal. « High Yield Dihydroxystearic Acid (DHSA) Based on Kinetic Model from Epoxidized Palm Oil ». Kemija u industriji 70, no 1-2 (2021) : 23–28. http://dx.doi.org/10.15255/kui.2020.016.

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In recent years, studies related to the epoxidation of fatty acids have garnered much interest due to the rising demand for eco-friendly epoxides derived from vegetable oils. From the epoxidation reaction, there is a side reaction involving epoxide and water. This reaction produces a by-product – dihydroxystearic acid (C<sub>18</sub>H<sub>36</sub>O<sub>4</sub>, DHSA). DHSA is one of the chemical precursors in the production of cosmetic products. Therefore, a kinetic model was developed to determine the optimised epoxidation process and concentration of DHSA, where each of the reactions was identified. The kinetic rate, <i>k</i> parameters obtained were: <i>k</i><sub>11</sub> = 6.6442, <i>k</i><sub>12</sub> = 11.0185, <i>k</i><sub>21</sub> = 0.1026 for epoxidation palm oleic acid, and <i>k</i><sub>41</sub> = 0.0021, <i>k</i><sub>51</sub> = 0.0142 in degradation process. The minimum error of the simulation was 0.0937. In addition, DHSA yield optimisation was done through Taguchi method, and the optimum conditions obtained were H<sub>2</sub>O<sub>2</sub>/oleic acid – OA unsaturation molar ratio 1 : 1 (level 2), formic acid – FA/OA unsaturation molar ratio 0.5 : 1 (level 1), temperature 35 °C (level 1), and agitation speed 100 rpm (level 1). A high yield of DHSA can be achieved under these conditions.
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34

Liang, Jing, Zhen Xing Cheng, Lian Yuan Wang, Hai Yan Zhu, Shi Gao et Xiao Ping Zhang. « Synthesis of Several Sugar Acetates and their Structures Characterization ». Advanced Materials Research 602-604 (décembre 2012) : 1373–78. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.1373.

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Several acetate esters were synthesized by reacting sugars, i.e. glucose, soluble starch, and dextrin, with acetic anhydride in the presence of some catalysts. Their structures were confirmed by IR and MS. Influences of the reaction conditions, such as catalyst and its dosage, reaction time, reaction temperature and acetic anhydride content, on the value of degree of substitution (DS) and the yield for starch acetates had also been investigated. Results showed that glucose could be easily completely acetylated; acidic catalyst tended to form a configuration of α-glucose penta-acetate (α-GPA), while alkaline catalyst β-GPA. However, soluble starch and dextrin were more difficult to be completely substituted by acetic anhydride. The DS value of soluble starch was below 2; for dextrin, its DS value could reach 2.3, close to the theoretical value of 3. An appropriate reaction temperature and reaction time were important for high yield as well as high DS value.
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35

Haydar, Lolwa, Wassim El Malti, Vincent Ladmiral, Ali Alaaeddine et Bruno Ameduri. « Original Fluorinated Non-Isocyanate Polyhydroxyurethanes ». Molecules 28, no 4 (14 février 2023) : 1795. http://dx.doi.org/10.3390/molecules28041795.

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New fluorinated polyhydroxyurethanes (FPHUs) with various molar weights were synthesized via the polyaddition reaction of a fluorinated telechelic bis(cyclocarbonate) (bis-CC) with a diamine. The fluorinated bis-CC was initially synthesized by carbonylation of a fluorinated diepoxide, 1,4-bis(2′,3′-epoxypropyl)perfluorobutane, in the presence of LiBr catalyst, in high yield. Then, several reaction conditions were optimized through the model reactions of the fluorinated bis-CC with hexylamine. Subsequently, fluorinated polymers bearing hydroxyurethane moieties (FPHUs) were prepared by reacting the bis-CC with different hexamethylenediamine amounts in bulk at 80 °C and the presence of a catalyst. The chemoselective polymerization reaction yielded three isomers bearing primary and secondary hydroxyl groups in 61–82% yield. The synthesized fluorinated CCs and the corresponding FPHUs were characterized by 1H, 19F, and 13C NMR spectroscopy. They were compared to their hydrogenated homologues synthesized in similar conditions. The gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) data of the FPHUs revealed a higher molar mass and a slight increase in glass transition and decomposition temperatures compared to those of the PHUs.
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36

Bentley, Keith W., Peng Zhang et Christian Wolf. « Miniature high-throughput chemosensing of yield, ee, and absolute configuration from crude reaction mixtures ». Science Advances 2, no 2 (février 2016) : e1501162. http://dx.doi.org/10.1126/sciadv.1501162.

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High-throughput experimentation (HTE) has emerged as a widely used technology that accelerates discovery and optimization processes with parallel small-scale reaction setups. A high-throughput screening (HTS) method capable of comprehensive analysis of crude asymmetric reaction mixtures (eliminating product derivatization or isolation) would provide transformative impact by matching the pace of HTE. We report how spontaneous in situ construction of stereodynamic metal probes from readily available, inexpensive starting materials can be applied to chiroptical chemosensing of the total amount, enantiomeric excess (ee), and absolute configuration of a wide variety of amines, diamines, amino alcohols, amino acids, carboxylic acids, α-hydroxy acids, and diols. This advance and HTS potential are highlighted with the analysis of 1 mg of crude reaction mixtures of a catalytic asymmetric reaction. This operationally simple assay uses a robust mix-and-measure protocol, is amenable to microscale platforms and automation, and provides critical time efficiency and sustainability advantages over traditional serial methods.
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37

Ghanbari, N., H. Ghafuri, H. Zand et M. Eslami. « Ball-Milling Promoted Monobromination Reactions : One-pot Regioselective Synthesis of Aryl Bromides and α-Bromoketones by NBS and Recyclable MCM-41-SO3H at Room Temperature ». SynOpen 01, no 01 (mars 2017) : 0143–46. http://dx.doi.org/10.1055/s-0036-1590959.

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An effective approach to monobromination reactions utilizing room temperature ball-milling is introduced for the synthesis of aryl bromides and bromoketones with N-bromosuccinimide (NBS) and MCM-41-SO3H. Advantages of this technique are short reaction times and high regioselectivity. In contrast to other techniques using microwaves, ultrasound, or ionic liquids, handling of sensitive materials is possible and furthermore, this method has advantages over other solvent-free techniques that require a higher reaction temperature for high yield of products.
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38

Zhao, Yuan, Bin Yang, Chongyu Zhu, Yaling Zhang, Shiqi Wang, Changkui Fu, Yen Wei et Lei Tao. « Introducing mercaptoacetic acid locking imine reaction into polymer chemistry as a green click reaction ». Polym. Chem. 5, no 8 (2014) : 2695–99. http://dx.doi.org/10.1039/c4py00058g.

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Some multicomponent reactions (MCRs) are similar to click reactions to give highly selective products with reliable high yield and effective atom utilization, implying that they can also be recognized as click reactions.
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39

Encinar, José, Ana Pardal, Nuria Sánchez et Sergio Nogales. « Biodiesel by Transesterification of Rapeseed Oil Using Ultrasound : A Kinetic Study of Base-Catalysed Reactions ». Energies 11, no 9 (25 août 2018) : 2229. http://dx.doi.org/10.3390/en11092229.

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The objective of this work was to study the acceleration that ultrasound causes in the rate of biodiesel transesterification reactions. The effect of different operating variables, such as ultrasound power, catalyst (KOH) concentration and methanol:oil molar ratio, was studied. The evolution of the process was followed by gas chromatography, determining the concentration of methyl esters at different reaction times. The biodiesel was characterized by its density, viscosity, saponification and iodine values, acidity index, water content, flash and combustion points, cetane index and cold filter plugging point (CFPP), according to EN 14214 standard. High methyl ester yield and fast reaction rates were obtained in short reaction times. Ultrasound power and catalyst concentration had a positive effect on the yield and the reaction rate. The methanol:oil molar ratio also increased the yield of the reaction, but negatively influenced the process rate. The reaction followed a pseudo-first order kinetic model and the rate constants at several temperatures were determined. The activation energy was also determined using the Arrhenius equation. The main conclusion of this work is that the use of ultrasound irradiation did not require any additional heating, which could represent an energy savings for biodiesel manufacture.
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40

Muzalevskiy, Vasiliy M., Zoia A. Sizova et Valentine G. Nenajdenko. « Synthesis and Reactions of 3-Halogenated 2-CF3-Indoles ». Molecules 27, no 24 (12 décembre 2022) : 8822. http://dx.doi.org/10.3390/molecules27248822.

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Halogenation of 2-trifluoromethylindole afforded 3-chloro-, 3-bromo- and 3-iodo derivatives in up to 98% yield. Methyl-, benzyl- and tosyl-groups can be installed at the nitrogen atom of prepared indoles in high yields by base catalyzed reaction with the corresponding alkylating (sulfonylating) reagents. A high synthetic utility of the prepared haloindoles in the reaction with various nucleophilies was shown. The reaction with 4-methylthiophenol and copper cyanide afforded the corresponding sulfides and nitriles in high yield. Palladium catalyzed cross-coupling with phenyl boronic acid and phenylacetylene gave the corresponding 3-phenyl-2-CF3-indoles and acetylenic derivatives in 72–98% yield.
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41

Mo, Bing Hui, Yu Huai Yu, Rong Ping Hu, Liang Wu, Huan Liao et Xue Min Cui. « The Synthesis and Characterization of New-Style Anticorrosive Pigment Zinc Molybdate ». Advanced Materials Research 634-638 (janvier 2013) : 467–71. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.467.

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Making use of the amphoteric characteristic of zinc oxide and the weak acidity of hydrolyzed ammonium heptamolybdate, we synthesized high-purity zinc molybdate through chemical reactions. At optimum reaction temperature of 70°C, 1 hour of reaction time and reuse of mother liquor, the molybdenum yield exceed 98%. This process has no wastewater discharge, and the products can be easily filtered. The productivity is significantly increased.
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42

Tommasi, Immacolata C. « Carboxylation of Hydroxyaromatic Compounds with HCO3− by Enzyme Catalysis : Recent Advances Open the Perspective for Valorization of Lignin-Derived Aromatics ». Catalysts 9, no 1 (3 janvier 2019) : 37. http://dx.doi.org/10.3390/catal9010037.

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This review focuses on recent advances in the field of enzymatic carboxylation reactions of hydroxyaromatic compounds using HCO3− (as a CO2 source) to produce hydroxybenzoic and other phenolic acids in mild conditions with high selectivity and moderate to excellent yield. Nature offers an extensive portfolio of enzymes catalysing reversible decarboxylation of hydroxyaromatic acids, whose equilibrium can be pushed towards the side of the carboxylated products. Extensive structural and mutagenesis studies have allowed recent advances in the understanding of the reaction mechanism of decarboxylase enzymes, ultimately enabling an improved yield and expansion of the scope of the reaction. The topic is of particular relevance today as the scope of the carboxylation reactions can be extended to include lignin-related compounds in view of developing lignin biorefinery technology.
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43

Lai, Wenchuan, Jiaxiang Liu, Longbo Luo, Xu Wang, Taijun He, Kun Fan et Xiangyang Liu. « The Friedel–Crafts reaction of fluorinated graphene for high-yield arylation of graphene ». Chemical Communications 54, no 72 (2018) : 10168–71. http://dx.doi.org/10.1039/c8cc05762a.

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Herein, we report the Friedel–Crafts reaction of fluorinated graphene with aryl molecules including methylbenzene, chlorobenzene and polystyrene, which achieved high-yield arylation functionalization of graphene under mild conditions.
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44

Santiago, Denise Ester O., et Bryan B. Pajarito. « Parametric Study of Silica Precipitation from Geothermal Brine ». Key Engineering Materials 705 (août 2016) : 121–25. http://dx.doi.org/10.4028/www.scientific.net/kem.705.121.

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The effects of reaction temperature, reaction time, and concentration of sodium hydroxide (NaOH) on yield and spectral similarity correlation (Corr) of silica harvested from geothermal brine are determined. The yield of geothermal silica is observed to increase when the reaction temperature is decreased, and when reaction time and NaOH concentration are increased. The Corr value is observed to increase when reaction temperature, reaction time, and NaOH concentration are decreased. The main effect of NaOH concentration and temperature significantly affects the yield and Corr of geothermal silica, respectively. To produce geothermal silica of high yield and spectral similarity to commercial silica filler for polymer, the optimum condition to precipitate silica from geothermal brine is predicted at temperature= 28°C, reaction time=12 h, and NaOH concentration= 7.5 %w/w.
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45

Inoue, N., Y. Goto, T. Sugiyama, H. Seki, K. Watanabe et Y. Kawamura. « Infrared Defect Dynamics of Irradiation Induced Complexes in CZ Silicon - C-Rich Case ». Solid State Phenomena 205-206 (octobre 2013) : 228–33. http://dx.doi.org/10.4028/www.scientific.net/ssp.205-206.228.

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Irradiation induced complexes of C-rich case in silicon crystal were examined by the highly sensitive and accurate infrared absorption spectroscopy. Low impurity concentration and high quality crystal was used and low dose was employed to make the reaction simple. Almost all possible absorption lines were revealed and their absorbance determined. The conversion coefficient from absorbance to the complex concentration was estimated by the plausible assumptions. The reaction was discussed in terms of concentration rather than absorbance. Intra-group reaction, chain reaction of successive addition of oxygen or self-interstitial, reaction yield and competition between the parallel reactions were described.
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46

Tao, Furong, Huanling Song et Lingjun Chou. « Efficient process for the conversion of xylose to furfural with acidic ionic liquid ». Canadian Journal of Chemistry 89, no 1 (janvier 2011) : 83–87. http://dx.doi.org/10.1139/v10-153.

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An efficient and simple process for the dehydration of xylose into furfural was studied, which was catalyzed by 1-(4-sulfonic acid)butyl-3-methylimidazolium hydrogen sulfate (IL-1) under mild conditions. A xylose conversion of 95.3% with a furfural yield of 91.45% was achieved in a 25 min reaction time at 150 °C; the xylose conversion and furfural yield greatly depended on the operation conditions, such as reaction time and temperature. IL-1 could be recycled and exhibited constant activity for five successive trials. This system was an important improvement, relative to the reactions using mineral acids at high temperatures, for further development on a pilot scale.
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47

Fuchs, Hendrik, Sascha Albrecht, Ismail–Hakki Acir, Birger Bohn, Martin Breitenlechner, Hans-Peter Dorn, Georgios I. Gkatzelis et al. « Investigation of the oxidation of methyl vinyl ketone (MVK) by OH radicals in the atmospheric simulation chamber SAPHIR ». Atmospheric Chemistry and Physics 18, no 11 (7 juin 2018) : 8001–16. http://dx.doi.org/10.5194/acp-18-8001-2018.

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Abstract. The photooxidation of methyl vinyl ketone (MVK) was investigated in the atmospheric simulation chamber SAPHIR for conditions at which organic peroxy radicals (RO2) mainly reacted with NO (“high NO” case) and for conditions at which other reaction channels could compete (“low NO” case). Measurements of trace gas concentrations were compared to calculated concentration time series applying the Master Chemical Mechanism (MCM version 3.3.1). Product yields of methylglyoxal and glycolaldehyde were determined from measurements. For the high NO case, the methylglyoxal yield was (19 ± 3) % and the glycolaldehyde yield was (65 ± 14) %, consistent with recent literature studies. For the low NO case, the methylglyoxal yield reduced to (5 ± 2) % because other RO2 reaction channels that do not form methylglyoxal became important. Consistent with literature data, the glycolaldehyde yield of (37 ± 9) % determined in the experiment was not reduced as much as implemented in the MCM, suggesting additional reaction channels producing glycolaldehyde. At the same time, direct quantification of OH radicals in the experiments shows the need for an enhanced OH radical production at low NO conditions similar to previous studies investigating the oxidation of the parent VOC isoprene and methacrolein, the second major oxidation product of isoprene. For MVK the model–measurement discrepancy was up to a factor of 2. Product yields and OH observations were consistent with assumptions of additional RO2 plus HO2 reaction channels as proposed in literature for the major RO2 species formed from the reaction of MVK with OH. However, this study shows that also HO2 radical concentrations are underestimated by the model, suggesting that additional OH is not directly produced from RO2 radical reactions, but indirectly via increased HO2. Quantum chemical calculations show that HO2 could be produced from a fast 1,4-H shift of the second most important MVK derived RO2 species (reaction rate constant 0.003 s−1). However, additional HO2 from this reaction was not sufficiently large to bring modelled HO2 radical concentrations into agreement with measurements due to the small yield of this RO2 species. An additional reaction channel of the major RO2 species with a reaction rate constant of (0.006 ± 0.004) s−1 would be required that produces concurrently HO2 radicals and glycolaldehyde to achieve model–measurement agreement. A unimolecular reaction similar to the 1,5-H shift reaction that was proposed in literature for RO2 radicals from MVK would not explain product yields for conditions of experiments in this study. A set of H-migration reactions for the main RO2 radicals were investigated by quantum chemical and theoretical kinetic methodologies, but did not reveal a contributing route to HO2 radicals or glycolaldehyde.
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48

Salih, Nadia, et Jumat Salimon. « Optimization of High Yield Epoxidation of Malaysian Castor Bean Ricinoleic Acid with Performic Acid ». Indonesian Journal of Chemistry 22, no 1 (3 avril 2022) : 609. http://dx.doi.org/10.22146/ijc.68592.

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Epoxidized castor oil (ECO) has shown high potential for industrial applications as value-added products such as polymer coating, plasticizer, and biolubricant. Epoxidized ricinoleic acid recovered from ECO has potential for industrial usage. In this work, epoxidized ricinoleic acid (ERA) was synthesized through in situ generated performic acid epoxidation of ricinoleic acid (RA). The epoxidation process was optimized by several reaction parameters, such as the molar ratio of formic acid to ethylenic unsaturation, the molar ratio of hydrogen peroxide to ethylenic unsaturation, and reaction temperature. The response reaction parameters of oxirane oxygen content (OOC) and iodine value (IV) were then evaluated. The results showed the optimal condition for the epoxidation of RA was obtained at 50 °C, the molar ratio of formic acid and hydrogen peroxide to ethylenic unsaturation of 1:8:1 for 4 h reaction time. A high yield of ERA of 86% with relative conversion into oxirane of 85.3% was achieved at the optimum condition. The optimum ERA showed a high OOC value of 4.00% and a low IV value of 2.24 mg/g. It is plausible that ERA can be used as an intermediate starting material to prepare value-added products such as biosurfactants, biopolymer additives, or biolubricants.
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49

Rizzacasa, MA, et MV Sargent. « The Wittig Reaction of 2-t-Butoxycarbonyl-1-methoxycarbonylethylidenetriphenylphosphorane : A Surrogate for the Stobbe Reaction ». Australian Journal of Chemistry 40, no 10 (1987) : 1737. http://dx.doi.org/10.1071/ch9871737.

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The reaction of 2-t-butoxycarbonyl-l-methoxycarbonylethylidenetriphenylphosphorane (3) with a range of aromatic aldehydes has been explored. The resultant itaconic esters, obtained in high yield, are readily converted into methyl 4-acetoxynaphthalene-2-carboxylates.
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50

Roper, Kimberley A., Malcolm B. Berry et Steven V. Ley. « The application of a monolithic triphenylphosphine reagent for conducting Ramirez gem-dibromoolefination reactions in flow ». Beilstein Journal of Organic Chemistry 9 (2 septembre 2013) : 1781–90. http://dx.doi.org/10.3762/bjoc.9.207.

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The application of a monolithic form of triphenylphosphine to the Ramirez gem-dibromoolefination reaction using flow chemistry techniques is reported. A variety of gem-dibromides were synthesised in high purity and excellent yield following only removal of solvent and no further off-line purification. It is also possible to perform the Appel reaction using the same monolith and the relationship between the mechanisms of the two reactions is discussed.
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