- SELECTIVE ACETALIZATION / ETHERIFICATION PROCESS
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The present invention relates to a selective process for preparing acetals or ethers. In particular, the process involves a selective catalytic hydrogenolysis of a trihydrocarbyl orthoesterso as to control the extent of dealcoholation to afford either the corresponding acetal or ether product. Ether products preparable by means of the present invention include ethers which are suitable for use as base stocks in lubricating compositions.
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Page/Page column 19-21
(2019/05/10)
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- Careful investigation of the hydrosilylation of olefins at poly(ethylene glycol) chain ends and development of a new silyl hydride to avoid side reactions
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Hydrosilylation of olefin groups at poly(ethylene glycol) chain ends catalyzed by Karstedt catalyst often results in undesired side reactions such as olefin isomerization, hydrogenation, and dehydrosilylation. Since unwanted polymers obtained by side reactions deteriorate the quality of end-functional polymers, maximizing the hydrosilylation efficiency at polymer chain ends becomes crucial. After careful investigation of the factors that govern side reactions under various conditions, it was related that the short lifetime of the unstable Pt catalyst intermediate led to the formation of more side products under the inherently dilute conditions for polymers. Based on these results, two new chelating hydrosilylation reagents, tris(2-methoxyethoxy)silane (5) and 2,10-dimethyl-3,6,9-trioxa-2,10-disilaundecane (6), have been developed. It was demonstrated that the hydrosilylation efficiency at polymer chain ends was significantly increased by employing the internally coordinating hydrosilane 5. In addition, employment of the internally coordinating disilane species 6 in an addition polymerization with 1,5-hexadiene by hydrosilylation reaction yielded a polymer with high molecular weight (Mn = 9300 g/mol), which was significantly higher than that (Mn = 2600 g/mol) of the corresponding polymer obtained with non-chelating dihydrosilane, 1,1,3,3-tetramethyldisiloxane.
- Shin, Hyunseo,Moon, Bongjin
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p. 527 - 536
(2018/01/27)
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- CATALYTIC HYDROGENATION USING COMPLEXES OF BASE METALS WITH TRIDENTATE LIGANDS
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Complexes of cobalt and nickel with tridentate ligand PNHPR are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHPCy)Co(CH2SiMe3)]BArF4 (PNHPCy=bis[2-(dicyclohexylphosphino)ethyl]amine, BArF4=B(3,5-(CF3)2C6H3)4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60° C., 1-4 atm H2). Nickel complex [(PNHPCy)Ni(H)]BPh4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNPCy)Ni(H) was used for hydrogenating alkenes.
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Paragraph 0060; 0061
(2015/12/07)
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- Mild and homogeneous cobalt-catalyzed hydrogenation of C=C, C=O, and C=N bonds
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A cationic cobalt(II)-alkyl complex is an effective precatalyst for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (1-4 atm H2; see scheme). The catalyst shows a high functional-group tolerance across a broad range of substrates. Experiments suggest that the active catalytic species is a cobalt(II)-hydride complex. Copyright
- Zhang, Guoqi,Scott, Brian L.,Hanson, Susan K.
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supporting information
p. 12102 - 12106
(2013/01/16)
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- On the miscibility of ethers and perfluorocarbons. An experimental and theoretical study
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Despite their significant polar character, some organic ethers such as diethyl ether were found to be miscible with perfluorocarbon solvents. Solubilities of various ethers in perfluorocarbons and miscibility temperatures were determined. These properties were found to be greatly dependent on the polarity but also size and shape of the ether molecule. Theoretical calculations of the miscibility temperatures of organic solvents and perfluorocarbons using COSMO-RS method were correlated with experimental data. Considering the difficulties in the accurate description of the macroscopic properties, such as miscibility temperatures, from the first principles, the agreement between experimental and theoretical data is reasonable.
- Babiak, Peter,Němcová, Adriana,Rulí?ek, Lubomír,Beier, Petr
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p. 397 - 401
(2008/12/21)
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- Reaction network of aldehyde hydrogenation over sulfided Ni-Mo/Al 2O3 catalysts
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A reaction network of aldehyde hydrogenation over NiMoS/Al 2O3 catalysts was studied with aldehydes with straight and branched carbon chains and different chain lengths as feed materials. The reactions in the gas phase and the liquid phase were compared. The main reaction in the aldehyde hydrogenation process is the hydrogenation of the CO double bond, which takes place over the coordinatively unsaturated sites. The major side reactions are self-condensation of aldehydes and condensation of aldehydes with alcohols. Both reactions involve α-hydrogen and are primarily catalyzed by acid-base bifunctional sites over the exposed Al2O 3 surfaces.
- Wang, Xueqin,Saleh, Ramzi Y.,Ozkan, Umit S.
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- The γ-silicon effect on solvolyses of the 3-(aryldimethylsilyl)propyl system
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The γ-silicon effects in solvolyses were studied mechanistically on 3-(aryldimethylsilyl)propyl tosylates in various solvents based on the substituent effects. The mechanism can be described as competing reactions of the γ-silyl-assisted (kSi) and the solvent-assisted (ks) pathways. Copyright
- Fujio, Mizue,Nakashima, Tohru,Fujiyama, Ryoji,Kim, Hyun-Joong,Tsuno, Yuho
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p. 612 - 615
(2007/10/03)
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- Concerning the Products of the Reaction of Methyl Bromide and Ethyl Bromide with Potassium Hydroxide in Aqueous Methanolic Solutions and the Progress of this SN2-Reaction
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Investigations of the reaction of methyl bromide and ethyl bromide with potassium hydroxide in methanolic and aqueous methanolic solutions show that the main products of these reactions are dimethyl ether and ethylmethyl ether. The reaction rates measured in methanolic or aqueous methanolic solutions are the same whether potassium hydroxide or potassium methoxide are used. These results are caused by an equilibrium between hydroxide and methoxide ions with which we could establish the equilibrium constant near 0.6. This means that a solution of sodium hydroxide c=0.1 moll-1 in methanol contains roughly 99.8% of methoxide ions. The reaction rates in methanolic as well as in aqueous methanolic solutions are strict second order. The reaction rate measured at several temperatures permitted the calculation of EA≠, ΔH≠, ΔS≠ and ΔG≠. Furthermore the kinetic investigations show that the nucleophilicity of methoxide ions is lower compared to hydroxide ions. The calculation of the Swain-Scott-parameter n results in a nucleophilicity scale in order to methoxide, hydroxide, ethoxide ions. The kinetic investigations of the reaction of ethyl bromide with methoxide and hydroxide ions in methanolic solutions demonstrate that at high temperatures the rate constant of methoxide ions is higher than that of hydroxide ions. The opposite case can be observed at lower temperatures. At the temperature of 20°C the rate constants of both reactions are equal. This is to do with the isokinetic effect which one is rarely able to observe at room temperatures.
- Friedrich,Sonnefeld,Jansen
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- Hydrolysis and Alcoholysis of Esters of o-Nitrobenzenesulfonic Acid
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The rate of solvolysis of esters of o-nitrobenzenesulfonic acid with water and C1-C4 alcohols is satisfactorily described by two-parametric Hammett-Taft equation with predominating effect of the electronic factor σ*. The effect of the structure of the hydrocarbon rest in the sulfonic ester group does not fit to this relationship.
- Sendega,Makitra,Pirig
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p. 1438 - 1446
(2007/10/03)
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- Triazene Drug Metabolites. Part 10. Metal-ion Catalysed Decomposition of Monoalkyltriazenes in Ethanol Solutions
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The metal ions Fe(2+), Zn(2+) and Cu(2+) bring about the rapid decomposition of 1-aryl-3-alkyltriazenes to the corresponding anilines.For Fe(2+), a linear dependence of the pseudo-first-order rate constant, k0, on was observed, while for Zn(2+) and Cu(2+) plots of k0 versus were curved and indicative of complex formation.For Fe(2+), second-order rate constants k2Fe(2+) for substituted 1-aryl-3-methyltriazenes follow a Hammett relationship giving rise to a ρ value of -3.0.For Zn(2+) and Cu(2+), the data were analysed in terms of an equilibrium konstant, KM(2+), for the dissociation of a metal-ion-triazene complex and the first-order rate constant, for the collapse of this complex to products, k2M(2+).Hammett ρ values of 1.0 for both KZn(2+) and KCu(2+) are found, and the corresponding ρ values for k2Zn(2+) and k2Cu(2+) are -1.3 and -1.9.There is reasonable correlation between the Taft Eg parameter for the alkyl group and KCu(2+), giving a δ value of -1.6.The dependence of k2Cu(2+) on the alkyl group is not simple: k2Cu(2+) decreases in the order Pr > Et * PhCH2 ca. 4-MeOC6H4CH2 > CD3 ca.Me.The reactions catalysed by Cu(2+) are inhibited by added nucleophiles e.g.Br(1-) and N-methylimidazole. A mechanism is proposed in which the triazene complexes to the metal ion via the N(1) nitrogen atom of the E-cis conformer, then undergoes a fast proton transfer to form a complex involving the unconjugated tautomer which subsequently decomposes via unimolecular scission of the N(2)-N(3) bond to form an alkyldiazonium ion and an aniline-metal complex.The observed products then arise from rapid solvolysis of the metal-aniline complex and the alkyl diazonium ion.
- Iley, Jim,Moreira, Rui,Rosa, Eduarda
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- Empirical Correlations of Partial Molar Volumes at Infinite Dilution of Organic Solutes and Transition State for SN2 Hydrolysis and Ethanolysis of n-Alkyl Bromides
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Pseudo-first-order rate constants under pressures 3 mol-1) were ca. -11 for the hydrolysis and about -25 for the ethanolysis.Partial molar volumes at infinite dilution were measured for n-butyl bromide in water at 298.15 K and for 66 organic solutes in ethanol at 333.15 K.Partial molar volumes of the transition states are shown to be adaptable to volumetric behaviour for common solutes, in which the partial molar volume of each solute is compared with that of the n-alkane having the same van der Waals volume.
- Itsuki, Hidenori,Kuwabara, Mikizo,Hayase, Kouji,Terasawa, Seiji
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p. 563 - 572
(2007/10/02)
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- Hydrocarbonylation of linear and branched aliphatic C2-C4 alcohols catalyzed by cobalt-ruthenium systems. A comparative study.
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In an extension of studies of the hydrocarbonylation of C2-C4 alcohols in the presence of a bimetallic catalyst system at high Syngas pressures to yield the next higher homologue, the effect of the catalytic system based on cobalt and ruthenium compounds promoted by iodine or iodides has been examined.For the optimal Co/Ru ratio the selectivity for the higher alcohol is highest because of a large decrease in the extent of hydrocarbon and ether formation.Neither this ratio nor the optimal pressure depends on the structure of the alcohol.It is suggested that the synergism observed in Co-Ru-catalyzed hydrocarbonylation of alcohols is due to a cocatalytic effect of the Ru catalyst involving reaction of ruthenium hydrides with acyl-cobalt complexes.The mechanism is consistent with the suggestion that there is an intermediate olefin that undergoes hydroformylation in a subsequent step.
- Jenner, Gerard
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p. 237 - 252
(2007/10/02)
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- Chemistry of Carbenes: Part I - Reactions of Methylene with Diethyl Ether
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The carbene biradical, methylene, reacts with diethyl ether to give in addition to insertion products (ethyl n-propyl and ethyl isopropyl ethers), a methyl alkyl ether by a displacement reaction and acetaldehyde by an abstraction reaction in which the biradical behaves like a monoradical.The insertion reactions have been found to show clear discrimination.The bond reactivity of secondary C-H bond is 2.53 at 20 and 2.85 at 100 deg C, whereas for that of Et-O bond is 0.90 at 20 and 1.14 at 100 deg C in comparison to 1.00 for primary C-H bond.At 100 deg C the H-abstraction rate is 1.00 although individual runs show variation.The cumulative rate of attack at 100 deg C is thus about 3.8 times greater on secondary bond as compared to that at the primary bond.The addition of oxygen to the system not only alters the course of the reactions but results in the formation of novel peroxy biradicals and monoradicals which give rise to large amounts of ethyl acetate and ethyl formate.
- Mehta, R. K. S.
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p. 1239 - 1243
(2007/10/02)
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- Onium Ylide Chemistry. 3. Evidence for Competing Oxonium Ylide Formation with C-H Insertion in Meerwein's Reaction of Methylene and Methylene-d2 with Dialkyl Ethers
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Meerwein's reaction of singlet methylene, produced by photolysis of diazomethane, with dialkyl ethers has been reinvestigated on the basis of reactions using CD2N2.In competition with methylene insertion into the various C-H bonds, about 10percent of methyl alkyl ether and small amounts of dimethyl ether formation are also observed.This indicates evidence for competing attack of methylene on oxygen leading to the corresponding intermediate methylenedialkyloxonium ylides which are immediately protonated by methyl alkohol (or water)impurity present in the reaction medium togive the corresponding methyldialkyloxonium ions.Dealkylative cleavage of the latter gives the observed methyl alkyl ethers.By the use of deuterium-labeled diazomethane CD2N2 it has been shown that ethylene and propylene formed under the reaction conditions are coming predominantly from diazomethane itself and not via intramolecular β-elimination of the oxonium ylides.
- Olah, George A.,Doggweiler, Hans,Felberg, Jeff D.
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p. 2116 - 2120
(2007/10/02)
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- HYDROGENATION OF 3-ETHOXY-1-PROPENE CATALYZED BY SUPPORTED NICKEL CATALYSTS.
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Nickel catalysts supported on different kinds of metal oxides were prepared to search for active catalysts for 3-ethoxy-1-propene hydrogenation. Ni/ThO//2 and Ni/SiO//2-Al//2O//3 catalysts exhibited high activity and selectivity for 1-ethoxypropane, while Ni/MgO, Ni/CaO, and Ni/La//2O//3 catalysts preferentially catalyzed double bond migration to 1-ethoxy-1-propene which undergo hydrogenation with difficulty.
- Matsuhashi,Hattori
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p. 3323 - 3324
(2007/10/02)
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