Relevant bibliographies by topics / Ethoxide

Academic literature on the topic 'Ethoxide'

Author: Grafiati
Published: 1 April 2023

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Journal articles on the topic "Ethoxide"

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Balakrishnan, Vimal K., Julian M. Dust, Gary W. vanLoon, and Erwin Buncel. "Catalytic pathways in the ethanolysis of fenitrothion, an organophosphorothioate pesticide. A dichotomy in the behaviour of crown/cryptand cation complexing agents." Canadian Journal of Chemistry 79, no. 2 (February 1, 2001): 157–73. http://dx.doi.org/10.1139/v01-006.

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The rates of displacement of 3-methyl-4-nitrophenoxide ion from the pesticide, fenitrothion, by alkali metal ethoxides in anhydrous ethanol were followed spectrophotometrically. Through product analysis experiments, which included 31P NMR and GC-MS, as well as spectrophotometric analysis, three reaction pathways were identified: nucleophilic attack at the phosphorus centre, attack at the aliphatic carbon, and a minor SNAr route ([Formula: see text]7%). Furthermore, a consecutive process was found to occur on the product of attack at the phosphorus centre. For purposes of kinetic treatment, the processes at the aliphatic and aromatic carbon were combined (i.e., the minor SNAr pathway was neglected), and the observed reaction rate constants were dissected into rate coefficients for nucleophilic attack at phosphorus and at aliphatic carbon. Attack at phosphorus was found to be catalyzed by the alkali metal ethoxides in the order KOEt > NaOEt > LiOEt. Catalysis arises from alkali metal ethoxide aggregates in the base solutions used (0–1.8 M); treatment of the system as a mixture of free ethoxide, ion-paired metal ethoxide, and metal ethoxide dimers resulted in a good fit with the kinetic data. An unexpected dichotomy in the kinetic behaviour of complexing agents (e.g., DC-18-crown-6, [2.2.2]cryptand) indicated that the dimers are more reactive than free ethoxide anions, which are in turn more reactive than ion-paired metal ethoxide. The observed relative order of reactivity is explained in the context of the Eisenman theory in which the free energy of association of the metal ion with the rate-determining transition state is largely determined by the solvent reorganization parameter. In contrast with displacement at the phosphorus centre, attack at the aliphatic carbon was not found to be catalyzed by alkali metals. In this case, the free ethoxide anion was more reactive than either the ion-paired metal ethoxide or the dimeric aggregate. The differing effects of alkali metals on the two pathways is ascribed largely to the leaving group pKa. For carbon attack, the pKa value estimated for demethyl fenitrothion, 2.15, is sufficiently low that metal ions are not required to stabilize the rate-determining transition state. In contrast, for phosphorus attack, 3-methyl-4-nitrophenoxide, with a pKa of 7.15, requires stabilization by metal ion interactions. Hence, alkali metal ions catalyze attack at phosphorus, but not attack at the carbon centres.Key words: organophosphorothioate, pesticide, fenitrothion, ethanolysis, alkali metal ethoxide, ion-pair reactivity, dimers, catalysis, competitive pathways.
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2

Pregel, Marko J., Edward J. Dunn, and Erwin Buncel. "Metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. III. Catalysis vs. inhibition by metal ions in the reaction of p-nitrophenyl benzenesulfonate with ethoxide." Canadian Journal of Chemistry 68, no. 10 (October 1, 1990): 1846–58. http://dx.doi.org/10.1139/v90-287.

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The rate of the nucleophilic displacement reaction of p-nitrophenyl benzenesulfonate (1) with alkali metal ethoxides in ethanol at 25 °C has been studied by spectrophotometric techniques. For lithium ethoxide, sodium ethoxide, potassium ethoxide, and cesium ethoxide, the observed rate constants increase in the order LiOEt < NaOEt < CsOEt < KOEt. The effect of added crown ether and cryptand complexing agents was also investigated. Addition of complexing agent to the reaction of KOEt results in the rate decreasing to a minimum value corresponding to the reaction of free ethoxide. Conversely, addition of complexing agent to the reaction of LiOEt results in the rate increasing to a maximum value that is identical to the minimum value seen in the reaction of KOEt in the presence of excess complexing agent. In complementary experiments, alkali metal ions were added in the form of unreactive salts. Addition of a K+ salt to the reaction of KOEt increases the reaction rate, while addition of a Li+ salt to the reaction of LiOEt decreases the rate. The involvement of metal ions in the reaction of 1 is proposed to occur via reactive alkali metal – ethoxide ion pairs. The kinetic data are analyzed in terms of an ion pairing treatment that allows the calculation of second-order rate constants for free ethoxide and metal–ethoxide ion pairs; the rate constants increase in the order LiOEt < EtO−< NaOEt < CsOEt < KOEt. Thus, Li+isaninhibitorofthereactionofethoxidewith1, whiletheothermetalsionsstudiedareallcatalysts. Equilibrium constants for the association of the various metal ions with the transition state are calculated using a thermodynamic cycle, and are compared to association constants in the ground state. Consistent with the observed kinetic results, Li+ is found to stabilize the ground state more than the transition state, while Na+, K+, and Cs+ all stabilize the transition state more than the ground state. The trend in the magnitude of the transition state stabilization is interpreted in terms of interactions of the transition state with bare or solvated metal ions. It is concluded that the transition state for the reaction of 1 with ethoxide forms solvent separated ion pairs with alkali metal ions. Analogous data were available for the reaction of p-nitrophenyl diphenylphosphinate (2) with ethoxides, where Li+, Na+, K+, and Cs+ all function as catalysts, and the results are analyzed as above. In contrast to the sulfonate system, it is proposed that the phosphinate transition state forms contact ion pairs with alkali metal ions. The difference is attributed to a greater localization of negative charge in the phosphinate transition state, leading to stronger interactions with metal ions, which overcome metal ion – solvent interactions. Keywords: nucleophilic substitution at sulfur, alkali metal ion catalysis.
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Dunn, Edward J., and Erwin Buncel. "Metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. I. Catalysis by metal ions in the reaction of p-nitrophenyl diphenylphosphinate with ethoxide." Canadian Journal of Chemistry 67, no. 9 (September 1, 1989): 1440–48. http://dx.doi.org/10.1139/v89-220.

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The effect of macrocyclic crown ether and cryptand complexing agents on the rate of the nucleophilic displacement reaction of p-nitrophenyl diphenylphosphinate by alkali metal ethoxides in ethanol at 25 °C has been studied by spectrophotometric techniques. For the reactions of potassium ethoxide, sodium ethoxide, and lithium ethoxide, the observed rate constant increased in the order KOEt < NaOEt < LiOEt. Crown ether and cryptand cation-complexing agents have a retarding effect on the rate. Increasing the ratio of complexing agent to base results in a decrease in kobs to a minimum value corresponding to the rate of reaction of free ethoxide ion. In complementary experiments, alkali metal ions were added to these reaction systems in the form of unreactive salts, causing an increase in reaction rate. The kinetic data were analysed in terms of ion-pairing treatments, which allowed evaluation of rate coefficients due to free ethoxide ions and metal ion – ethoxide ion pairs. Possible roles of the metal cations are discussed in terms of ground state and transition state stabilization. Evaluation of the equilibrium constants for association of the metal ion with ground state (Ka) and the transition state (K′a) shows that catalysis occurs as a result of enhanced association between the metal ion and the transition state, with (K′a) values increasing in the order K+ < Na+ < Li+. A model is proposed in which transition state stabilization arises largely from chelation of the solvated metal ion to two charged oxygen centers. This appears to be the first reported instance of catalysis by alkali metal cations in nucleophilic displacement at phosphoryl centers. Keywords: nucleophilic displacement at phosphorus, alkali-metal-ion catalysis.
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Joshi, Vikram, and Martha L. Mecartney. "The influence of water of hydrolysis on microstructural development in sol-gel derived LiNbO3 thin films." Journal of Materials Research 8, no. 10 (October 1993): 2668–78. http://dx.doi.org/10.1557/jmr.1993.2668.

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The effect of water of hydrolysis on nucleation, crystallization, and microstructural development of sol-gel derived single phase LiNbO3 thin films has been studied using transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray diffraction (XRD), and differential scanning calorimetry (DSC). A precursor solution of double ethoxides of lithium and niobium in ethanol was used for the preparation of sol. DSC results indicated that adding water to the solution for hydrolysis of the double ethoxides lowered the crystallization temperature from 500 °C (no water) to 390 °C (2 moles water per mole ethoxide). The amount of water had no effect on the short-range order in amorphous LiNbO3 gels but rendered significant microstructural variations for the crystallized films. AFM studies indicated that surface roughness of dip-coated films increased with increasing water of hydrolysis. Films on glass, heat-treated for 1 h at 400 °C, were polycrystalline and randomly oriented. Those made with a low water-to-ethoxide ratio had smaller grains and smaller pores than films prepared from sols with higher water-to-ethoxide ratios. Annealing films with a low water concentration for longer times or at higher temperatures resulted in grain growth. Higher temperatures (600 °C) resulted in grain faceting along close-packed planes. Films deposited on c-cut sapphire made with a 1:1 ethoxide-to-water ratio and heat-treated at 400 °C were epitactic with the c-axis perpendicular to the film-substrate interface. Films with higher concentrations of water of hydrolysis on sapphire had a preferred orientation but were polycrystalline. It is postulated that a high amount of water increases the concentration of amorphous LiNbO3 building blocks in the sol through hydrolysis, which subsequently promotes crystallization during heat treatment.
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Brorson, Sverre-Henning. "How to Examine the Antigen-damaging Effect of Sodium Ethoxide on Deplasticized Epoxy Sections." Journal of Histochemistry & Cytochemistry 45, no. 1 (January 1997): 143–46. http://dx.doi.org/10.1177/002215549704500117.

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The purpose of this investigation was to develop a method that could be used to estimate how damaging sodium ethoxide is to different antigens with respect to immunolabeling when epoxy sections are deplasticized. If we obtain weak labeling for an antigen on deplasticized epoxy sections, this might be caused by the damaging effect of the ethoxide solution. It is therefore interesting to develop a method to check if this really is the reason. Fibrin clots and tissues of human kidney and thyroid were embedded in LR White resin. Some thin sections from these specimen blocks were exposed to sodium ethoxide in the same way as epoxy sections are when being deplasticized. Other sections from the same blocks were not exposed to sodium ethoxide. Both categories of sections were immunogold-labeled with anti-fibrinogen, anti-thyroglobulin, anti-IgA, anti-IgG, or anti-IgM. The intensity of immunolabeling of sections treated with ethoxide was compared with the immunolabeling of corresponding sections that were not treated with ethoxide. No significant differences were found in immunolabeling for fibrinogen, IgA, IgG, and IgM. For thyroglobulin, the intensity was approximately 30% less in tissues that were exposed to sodium ethoxide. The practical significance of this method is that we easily can examine the degree to which a given antigen is affected by sodium ethoxide, which is the agent used for deplasticizing epoxy sections.
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Stirling, J. W., and P. S. Graff. "Antigen unmasking for immunoelectron microscopy: labeling is improved by treating with sodium ethoxide or sodium metaperiodate, then heating on retrieval medium." Journal of Histochemistry & Cytochemistry 43, no. 2 (February 1995): 115–23. http://dx.doi.org/10.1177/43.2.7529784.

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To optimize the ultrastructural localization of immunoglobulin G in corneal crystalloid deposits, we compared a range of antigen unmasking techniques. A human corneal biopsy specimen was fixed in formalin, post-osmicated, and embedded in epoxy resin for electron microscopy. Thin sections were immunogold-labeled for IgG after treatment with sodium ethoxide or sodium metaperiodate. Sections were also treated by heating them at 95 degrees C while they floated on water, 0.01 M citrate buffer (pH 6.0), or sodium metaperiodate. The treatments were applied separately and combined. After labeling, crystalloids in untreated sections had a probe density of 5 particles/microns2. Crystalloids in sections treated only with sodium ethoxide or sodium metaperiodate had probe densities of 15-20 particles/microns2. Sodium ethoxide combined with heating on water, or citrate buffer, gave probe densities of 140-160 particles/microns2. Sodium metaperiodate combined with heating on citrate buffer gave the highest probe density (195 particles/microns2). Although sodium ethoxide coupled with heating increased probe density, the ethoxide etched the sections and caused unacceptable damage. Treatment with sodium metaperiodate followed by heating on citrate buffer is recommended for antigen unmasking. This combination gave a high probe density and sections remained intact, with good ultrastructural detail.
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Hu, Qi-Shan, Lai-Cai Li, and Xin Wang. "Theoretical study on the mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile catalyzed by lithium ethoxide." Open Chemistry 6, no. 2 (June 1, 2008): 304–9. http://dx.doi.org/10.2478/s11532-008-0004-9.

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AbstractThe The mechanism of reaction between 3-hydroxy-3-methyl-2-butanone and malononitrile for the synthesis of 2-dicyanomethylene-4, 5, 5-trimethyl-2,5-dihydrofuran-3-carbonitrile catalyzed by lithium ethoxide was investigated by density functional theory (DFT). The geometries and the frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-31G(d) level. The vibration analysis and the IRC analysis verified the authenticity of transition states. The reaction processes were confirmed by the changes of charge density at the bond-forming critical point. The results indicated that lithium ethoxide is an effective catalyst in the synthesis of 2-dicyanomethylene-4, 5, 5-trimethyl-2, 5-dihydrofuran-3-carbonitrile from malononi-trile and 3-hydroxy-3-methyl-2-butanone. The activation energy of the reaction with lithium ethoxide was 115.86 kJ·mol−1 less than the uncatalyzed reaction. The mechanism of the lithium ethoxide catalyzed reaction differed from the mechanism of the uncatalyzed reaction.
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YANG, Haiping, Shenghai YANG, Motang TANG, and Bihui LI. "The Electrosynthesis of Tantalum Ethoxide." Electrochemistry 82, no. 9 (2014): 743–48. http://dx.doi.org/10.5796/electrochemistry.82.743.

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Rincón-Ortiz, Sergio A., Jhonatan Rodriguez-Pereira, and Rogelio Ospina. "Niobium ethoxide analyzed by XPS." Surface Science Spectra 27, no. 2 (December 2020): 024014. http://dx.doi.org/10.1116/6.0000472.

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Chammingkwan, Patchanee, Mingkwan Wannaborworn, Le Thi Tuyet Mai, Minoru Terano, Toshiaki Taniike, and Phairat Phiriyawirut. "Particle engineering of magnesium ethoxide-based Ziegler-Natta catalyst through post-modification of magnesium ethoxide." Applied Catalysis A: General 626 (September 2021): 118337. http://dx.doi.org/10.1016/j.apcata.2021.118337.

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Dissertations / Theses on the topic "Ethoxide"

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Kennedy, Steven Roger 1971. "Synthesis, characterization and use of peroxotungstic ethoxide as a precursor to wet-chemically derived tungsten oxide thin films." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/278554.

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In this work a new wet-chemical method of preparing tungsten oxide thin films is described. This involves the dissolution of tungsten metal in aqueous hydrogen peroxide and reaction with acetic acid to form an alcohol-soluble precursor. All synthesis stages of this new precursor, termed peroxotungstic ethoxide, are characterized to determine possible reactions. The chemical and microstructural evolution of films is described as a function of firing temperature, utilizing infrared spectroscopy, diffraction and other optical data. A novel method of increasing the crack-free thickness of the films is given: a combination of oxalic acid dihydrate as a solution additive and film firing under controlled humidity. With this combination, fired crack-free films up to one micron in thickness were prepared. Oxalic acid dihydrate roughened and also caused crystallization of these films at lower temperatures (250°C) than expected. These rougher films exhibited an improved electrochromic response, as measured by optical and electrochemical characterizations.
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Book chapters on the topic "Ethoxide"

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Devy, Jérôme, Fabrice Fleury, Olivier Duval, Jean-Claude Jardillier, and Igor Nabiev. "The role of sequence-specificity of DNA binding by benzo[c]phenanthiridines fagaronin and ethoxidine in their anti-topoisomerase I activity." In Spectroscopy of Biological Molecules: New Directions, 297–98. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4479-7_132.

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Kawęcki, R. "Using Titanium(IV) Ethoxide." In Sulfur, Selenium, and Tellurium, 1. Georg Thieme Verlag KG, 2011. http://dx.doi.org/10.1055/sos-sd-139-00094.

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Sato, R., and T. Kimura. "Alkaline Hydrolysis of Bis(selenocyanates) with Sodium Ethoxide." In Sulfur, Selenium, and Tellurium, 1. Georg Thieme Verlag KG, 2008. http://dx.doi.org/10.1055/sos-sd-039-01446.

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Keller, P. A. "Addition of Activated Methylene Compounds to α,β-Unsaturated Ketones with Elimination of Ethoxide." In Six-Membered Hetarenes with One Nitrogen or Phosphorus Atom, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-015-00547.

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Keglevich, Gy, and H. Szelke. "3-Methylene-2,3-dihydro-1-phosphole 1-Oxides by Thallium Ethoxide Mediated Conversion of 1-Benzyl-3-methyl-1-phospholium Salts." In Ene-X Compounds (X=S, Se, Te, N, P), 1. Georg Thieme Verlag KG, 2007. http://dx.doi.org/10.1055/sos-sd-033-00861.

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Taber, Douglass F. "The Deslongchamps Synthesis of (+)-Cassaine." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0091.

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Although the Na+-K+-ATPase inhibitor (+)-cassaine 4 was isolated from the bark of Erythrophleum guineense in 1935, the structure was not established until 1959. Intriguing features of 4 include the unsaturated amide and the axial secondary methyl group, both pendant to the C ring. Pierre Deslongchamps, now at Université Laval, envisioned (Org. Lett. 2013, 15, 6270) that the relative stereochemistry of the second­ary methyl could be established kinetically by intramolecular Michael addition of the enolate formed by the addition of the anion of 2 to the enone 1 to give 3. The sulfoxide 2 was readily prepared by the addition (Tetrahedron Lett. 1990, 31, 3969) of the anion derived from methyl phenyl sulfoxide to methyl crotonate. The enone 1 was prepared from commercial dihydrocarvone 5. Robinson annula­tion with ethyl vinyl ketone 6 (Tetrahedron 2000, 56, 3409) led to 7, that was reduc­tively methylated, reduced further, and protected to give 8. Oxidative cleavage of the pendant isopropenyl group followed by Baeyer–Villiger oxidation, hydrolysis, and further oxidation gave the ketone 9, that was methoxycarbonylated, then oxidized further to 1. The addition of the anion derived from 2 to 1 presumably gave initially the axial adduct. Subsequent intramolecular Michael addition then proceeded selectively to one face of the residual enone to give, after elimination of the sulfoxide, the enone 3. The anionic cascade annulation that formed the C ring having been accomplished, the ester of 3 was removed by exposure to ethoxide to give 10, having the alkene con­jugated with the B-ring ketone. Selective reduction followed by protection gave 11. In the course of the hydrogenolytic deprotection of the A-ring alcohol, selective hydrogenation of the tetrasubstituted alkene was also observed. Increasing the H2 pressure and extending the reaction time gave complete conversion to the desired 12, the rela­tive configuration of which was established by X-ray crystallography. A series of protection, reduction, and oxidation steps led to the C-ring ketone, that was methoxycarbonylated to give 14. Reduction followed by dehydration gave the unsaturated ester, that was reduced to the saturated ester with Mg in methanol. Reduction followed by oxidation then delivered the aldehyde 15. After some investi­gation, it was found that the aldehyde could be converted to the desired enol triflate by exposure to KHMDS and the Comins reagent.
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Conference papers on the topic "Ethoxide"

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Paul, Anam, Jinjun Liu, and Md Reza. "DISPERSED-FLUORESCENCE SPECTROSCOPY OF JET-COOLED CALCIUM ETHOXIDE RADICAL (CaOC2H5)." In 71st International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2016. http://dx.doi.org/10.15278/isms.2016.rj06.

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