- Reactions of diols with dimethyl carbonate in the presence of W(CO) 6 and Co2(CO)8
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Dimethoxyalkanes and dimethyl alkanediyl biscarbonates were synthesized by reactions of diols with dimethyl carbonate in the presence of tungsten and cobalt carbonyls. Optimal reactant and catalyst ratios and reaction conditions were found to ensure selective formation of dimethoxyalkanes or dimethyl alkanediyl biscarbonates.
- Khusnutdinov,Shchadneva,Mayakova
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p. 948 - 952
(2014/10/16)
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- Continuous acid-catalyzed methylations in supercritical carbon dioxide: Comparison of methanol dimethyl ether and dimethyl carbonate as methylating agents
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The development of high-yielding, "greener" chemistry-based routes for the continuous synthesis of methyl ethers are reported in this study. Ethers have been efficiently produced using a methodology which eliminates the use of toxic alkylating agents and reduces the waste generation that is characteristic of traditional etherification processes. For the first time it is shown that the use of acidic heterogeneous catalysts can successfully achieve etherification when using scCO2 as a reaction medium. Furthermore, the relative efficiencies of three alternative methylating agents, dimethyl carbonate, dimethyl ether and MeOH, have been compared and contrasted for the methylation of 1-octanol. Dimethyl carbonate has proven to be the superior methylating agent, demonstrating higher conversion and selectivity. Successful methylation of secondary alcohols, diols, carboxylic acids and amines using dimethyl carbonate in supercritical carbon dioxide has also been shown. Substrate structure was found to influence the temperature required to maximize the yield of the desired product, substrates with multiple hydroxyl groups requiring the highest temperatures.
- Gooden, Peter N.,Bourne, Richard A.,Parrott, Andrew J.,Bevinakatti, Han S.,Irvine, Derek J.,Poliakoff, Martyn
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experimental part
p. 411 - 416
(2011/04/22)
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- Thermodynamic stabilities of Cu+ and Li+ complexes of dimethoxyalkanes (MeO(CH2)nOMe, n = 2-9) in the gas phase: Conformational requirements for binding interactions between metal ions and ligands
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The relative free energy changes for the reaction ML+ = M + + L (M = Cu+ and Li+) were determined in the gas phase for a series of dimethoxyalkanes (MeO(CH2)nOMe, n = 2-9) by measuring the equilibrium constants of ligand-transfer reactions using a FT-ICR mass spectrometry. Stable 1:1 Cu+-complexes (CuL +) were observed when the chain is longer than n = 4 while the 1:2 complexes (CuL2+) were formed for smaller compounds as stable ions. The dissociation free energy for CuL+ significantly increases with increasing chain length, by 10 kcal mol-1 from n = 4 to 9. This increase is attributed to the release of constrain involved in the cyclic conformation of the Cu+-complexes. This is consistent with the geometrical and energetic features of the complexes obtained by the DFT calculations at B3LYP/6-311G level of theory. On the contrary, the corresponding dissociation free energy for LiL+ increases only 3 kcal mol -1 from n = 2 to 9, although the structures of the 1:1 Li +-complexes are also considered to be cyclic. From these results it is concluded that the Cu[MeO(CH2)nOMe]+ requires linear alignment for O-Cu-O, indicating the importance of sd σ hybridization of Cu+ in the first two ligands binding energy, while the stability of the Li+ complex is less sensitive to binding geometries except for the system forming a small ring such as n = 1 and 2. Copyright
- Mishima, Masaaki,Maeda, Hideyuki,Than, Soe,Irie, Maki,Kikukawa, Kiyoshi
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p. 616 - 623
(2007/10/03)
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- PRODUCTION PROCESS OF 3-ALKOXY-1-PROPANOLS, AND 3-ALKOXY-1-PROPANOLS OBTAINED BY THE PRODUCTION PROCESS
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In the presence of a catalyst containing at least one element selected from the group consisting of elements of the group III, lanthanoid elements and actinoid elements of the Periodic Table, an allyl alcohol is reacted with an alcohol compound. A method for efficiently producing 3-alkoxy-1-propanol in a single step using an alcohol as a starting material is provided.
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Page/Page column 64-65
(2008/06/13)
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- Conversion of dimethyl ether to diesel fuel additives via dielectric barrier discharges
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A high-efficient conversion of dimethyl ether (DME) to diesel fuel additives at ambient condition via dielectric-barrier discharges has been performed. The conversion of DME reaches a high value of 66.56% at a gas flow rate of 30 mL·min-1. The liquid obtained is a cetane number promoter of diesel fuels. The selectivity of liquid product is more than 40%.
- Jiang, Tao,Liu, Chang-Jun,Fan, Guo-Liang
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p. 322 - 323
(2007/10/03)
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- Fingerprinting a Transition-Structure Guest by a Building-Block Approach with an Incremental Series of Catalytic Hosts. Structural Requirements for Glyme and α,ω-Dimethoxyalkane Catalyses in N-Methylbutylaminolysis and Butylaminolysis of 4-Nitrophenyl Acetate in Chlorobenzene
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Glymes, H-(CH2OCH2)n-H, GLM(n), catalyze butylaminolysis of 4-nitrophenyl acetate in chlorobenzene.Values of kcat/Oxy, where Oxy is the number of oxygens in the catalyst, increase with oligomer length up to triglyme, GLM(4), and then plateau.Optimal catalysis on a per oxygen basis requires a -(CH2OCH2)4-fragment, which suggests a four-point recognition of the secondary ammonium ion of the zwitterionic tetrahedral intermediate (TI) (J.Org.Chem. 1991, 56, 2821-2826).Dissection of individual structural components and reassembly to the same structure of the complexverifies this model.The following kinetic studies of 4-nitrophenyl acetate in chlorobenzene have accomplished the task: (a) methylbutylaminolysis catalyzed by GLM(n), n = 2-4; (b) methylbutylaminolysis catalyzed by α,ω-dimethoxyalkanes, CH3O-(CH2)n-OCH3, DME(n), n = 2-10 and 12; and (c) butylaminolysis catalyzed by DME(n), n = 2-10 and 12.Experiment a has revealed that kcat/Oxy is the same for GLM(2) - GLM(4).Optimal catalysis for breakdown of a zwitterionic TI with one ammonium proton only requires a -(CH2OCH2)2-fragment.Experiment b has shown that kcat/Oxy is largest for DME(2) with the values for the remaining DMEs 2 - 2.5-fold lower.A -CH2CH2- is the best spacer between the two oxygens.Thus, bifurcated hydrogen-bond formation between the two oxygens and the one ammonium proton enhances catalysis.Experiment c has revealed that kcat/Oxy for DME(2) exceeds the remaining DMEs by 3 - 3.6-fold, except for DME(8) and DME(10), which have values of kcat/Oxy only 1.7-fold slower.DME(8), the carba analogue of GLM(4), likely binds the two ammonium protons individually with the two oxygens.DME(10) behaves similarly.GLM(4) catalysis of butylaminolysis identifies -(CH2OCH2)4- as an optimal size.DME(8) catalysis confirms this size, although the two catalysts stabilize the two-proton ammonium ion differently.GLM(4) catalyzes butylaminolysis by forming two bifurcated hydrogen bonds.This suggested structure defines the size of the ammonium ion, which agrees with X-ray structural studies of polyether-ammonium complexes.Mechanistic proposals of butylaminolysis of aryl esters require such an ion.The results of this study confirm the stucture of the ion in the rate-limiting step.This building-block approach is a method for "fingerprinting" ammonium ions in transition structures of ionogenic reactions.
- Hogan, John C.,Gandour, Richard D.
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- OXYGEN YLIDES-I. REACTIONS OF CARBENES WITH OXETANE
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The ylides generated from carbenes (:CH2, :CHCO2Et, :CHPh) and oxetane in the presence of methanol undergo Stevens rearrangement and protonation competitively, yielding tetrahydrofurans and 1,3-dialkoxycyclopropanes as major products.
- Friedrich, Klaus,Jansen, Ulrich,Kirmse, Wolfgang
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p. 193 - 196
(2007/10/02)
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- The Ionic Hydrogen Bond. 2. Multiple NH+...O and CH?+...O Bonds. Complexes of Ammonium Ions with Polyethers and Crown Ethers
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Complexes of ammonium ions RNH3+ (R = CH3, c-C6H11), (CH3)3NH+, and pyridineH+ with polyethers and crown ethers are observed in the gas phase in the abscence of the solvent effects.The dissociation energies, ΔH0D, of the RNH3+ polyether complexes range from 29.4 kcal mol-1 (for RNH3+*CH3OCH2CH2OCH3) to 46 kcal mol-1 (RNH3+*18-crown-6).The large ΔH0D values for complexes of polydentate ligands indicate multiple -NH+...O-hydrogen bonding.Such mutiple bonding can contribute up to 18 kcal mol-1 to the bonding in RNH3+*CH3(OCH2CH2)3OCH3 and 21 kcal mol-1 in RNH3+*18-crown-6.Multiple interactions are also evident in the (CH3)3NH+*polyether complexes where -CH?+...O-hydrogen bonding seems to occur; and consecutive -CH?+...O-bonds contribute approximately 6, 4, and 2 kcal/mol-1 respectively for up to three such bonds.Total ΔH0D values in the (CH3)3NH+*polyether complexes thus range from 26.7 kcal mol-1 in (CH3)3NH+*CH3O(CH2)2OCH3 to 41 kcal mol-1 in (CH3)3NH+*18-crown-6.Multiple interaction effects, possibly including van der Waals dispersion forces, are observed also in pyridineH+*polyether complexes.Large negative entropies in RNH3+*acyclic polyether complexes vs.RNH3+*cyclic crown ethers make the acyclic polyethers less efficient ligands.
- Meot-Ner (Mautner), Michael
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p. 4912 - 4915
(2007/10/02)
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