- Oxyfunctionalization with CpIrIII(NHC)(Me)L complexes
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A series of monomethyl CpIrIII complexes were synthesized and studied for the formation of methanol in water. Methanol yields of 75(4)% in the presence of O2 were obtained. From isotope labeling studies, it was determined that O2 is the source of the oxygen atom in the product. From kinetic studies, oxyfunctionalization appears to proceed by dissociation of an L-type ligand followed by O2 binding and insertion.
- Lehman, Matthew C.,Boyle, Paul D.,Sommer, Roger D.,Ison, Elon A.
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Read Online
- Catalytic hydrogenation of cyclic carbonates: A practical approach from CO2 and epoxides to methanol and diols
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As an economical, safe and renewable carbon resource, CO2 turns out to be an attractive C1 building block for making organic chemicals, materials, and carbohydrates.[1] From the viewpoint of synthetic chemistry,[2] the utilization of CO2 as a feedstock for the production of industrial products may be an option for the recycling of carbon.[3] On the other hand, the transformation of chemically stable CO2 represents a grand challenge in exploring new concepts and opportunities for the academic and industrial development of catalytic processes.[4] The catalytic hydrogenation of CO2 to produce liquid fuels such as formic acid (HCO 2H)[5] or methanol[6] is a promising solution to emerging global energy problems. Methanol, in particular, is not only one of the most versatile and popular chemical commodities in the world, with an estimated global demand of around 48 million metric tons in 2010, but is also considered as the key to weaning the world off oil in the future.[6e, f] Although the production of methanol has already been industrialized by the hydrogenation of CO with a copper/zinc-based heterogeneous catalyst at high temperatures (250-300°C) and high pressures (50-100 atm),[6e, 7] the development of a practical catalytic system for the hydrogenation of CO2 into methanol still remains a challenge, as high activation energy barriers have to be overcome for the cleavage of the C=O bonds of CO2, albeit with favorable thermodynamics.[8] Heterogeneous catalysis for the hydrogenation of CO 2 into CH3OH has been extensively investigated, and Cu/Zn-based multi-component catalyst was found to be highly selective with a long life, but under relatively harsh reaction conditions (250 °C, 50 atm).[3b, 6d] Therefore, the production of methanol from CO2 by direct hydrogenation under mild conditions is still a great challenge for both academia and industry.
- Han, Zhaobin,Rong, Liangce,Wu, Jiang,Zhang, Lei,Wang, Zheng,Ding, Kuiling
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supporting information
p. 13041 - 13045
(2013/03/13)
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- METHOD FOR PRODUCING DEUTERATED METHYL METHACRYLATE
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A method for producing MMA-d8 which includes a step of exchanging D in hydroxyl group of methanol-d4 represented by the formula: CD3OD with H to prepare the methanol-d3 represented by the formula CD3OH and simultaneously recovering a deuterium-containing compound, and a step of reacting methanol-d3 with sulfuric acid salt of methacrylic acid amide represented by the formula CD2=(CD3)CO(NH2·H2SO4) to prepare MMA-d8 represented by the formula: CD2=(CD3)COOCD3.
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Page/Page column 7
(2008/06/13)
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- MANUFACTURING METHOD OF DEUTERATED METHYL METHACRYLATE
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PROBLEM TO BE SOLVED: To provide an economical manufacturing method of methyl methacrylate-d8 (C5D8O2) which is excellent in both the deuteration rate and the chemical purity and is useful as a raw material for plastic optical fibers and optical waveguide materials having a low transmission loss.SOLUTION: Methyl methacrylate-d8 is manufactured using as raw materials readily available methanol-d4 and acetone-d6 with all hydrogen atoms thereof deuterated, where methanol-d4 is converted into methanol-d3 with its methyl group fully deuterated and methyl methacrylate-d8 is obtained from the thus-obtained methanol-d3 with its methyl group fully deuterated and acetone cyanhydrin-d6 prepared from acetone-d6. A deuterium-containing compound, recovered when methanol-d4 is converted into methanol-d3 with its methyl group fully deuterated, is reutilized as a part of raw materials for manufacturing methanol-d4 and acetone-d6.
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Page/Page column 10
(2010/02/11)
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- Unusual ionic hydrogen bonds: Complexes of acetylides and fluoroform
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Ion-molecule complexes of substituted acetylides, RCC- (R = tert-butyl, H, phenyl, p-tolyl), and fluoroform, HCF3, were studied using Fourier transform ion cyclotron resonance mass spectrometry. These complexes, RCC-·HCF3, all have complexation energies of approximately -19 kcal/mol and are, therefore, hydrogen bonded. The acetylides vary in basicity over a 6 kcal/mol range, but all have the same complexation energy with fluoroform. The structure of these complexes was verified by deuterium isotopic exchange reactions and equilibrium fractionation experiments. The relationship between acid-base thermochemistry and hydrogen bond stability is discussed.
- Chabinyc, Michael L.,Brauman, John I.
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p. 8739 - 8745
(2007/10/03)
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- Concerning the Mechanism for Bifunctional Catalysis in the Methanolysis of Methoxymethylphenoxyphenylsilane
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The formic acid-formate-catalyzed methanolysis of methoxy-d3-methylphenoxyphenylsilane (1D) was studied.The formation of phenol and the exchange of the deuterated methoxy group with solvent was studied as a function of total buffer concentration.Both processes show bifunctional catalysis involving a molecule of acid and a molecule of base in the transition state.The observation of bifunctional catalysis suggests a mechanism in which formation of the silicon-solvent bond is concerted with breaking of the silicon-leaving group bond (-OC6H5 or -OCD3).From analysis of the kinetic data it is concluded that the concerted bond-forming and bond-breaking processes do not occur on a pentavalent silicon species formed by a preequilibrium addition of solvent or formate anion to 1D.The results are interpreted in terms of a mechanism in which solvent attack occurs on a tetravalent silicon center with simultaneous breaking of the silicon leaving group bond.
- Dietze, Paul E.
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p. 5653 - 5662
(2007/10/02)
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- Hydrogen-deuterium-exchange reactions of methoxide-methanol clusters
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The tandem flowing afterglow-selected ion flow tube has been employed to measure rate coefficients for a series of 12 bimolecular isotope-exchange reactions of methoxide-methanol clusters. From these kinetic measurements the dissociation energies of several hydrogen-bonded dimers were determined: CH3O-·DOCH3 (28.3 ± 0.1 kcal/mol), CH3O-·HOCD3 (28.5 ± 0.1 kcal/mol), CH3O-·DOCD3 (28.1 ± 0.1 kcal/mol) CD3O-·HOCD3 (28.9 ± 0.1 kcal/mol), and CD3O-·DOCD3 (28.5 ± 0.1 kcal/mol). Differences in the bond strengths of these cluster ions can be understood in terms of the acidity of the neutral molecule and the basicity of the anion involved in the cluster; a given ion makes a stronger bond with a stronger acid while a given neutral molecule makes a stronger bond with a stronger base. By use of literature values of the electron affinity of the methoxy radicals along with the known RO-H and RO-D bond strengths, the gas-phase acidities (ΔH° acid) of CD3OD (383.9 ± 0.7 kcal/mol), CH3OD (383.5 ± 0.7 kcal/mol), and CD3OH (382.0 ± 0.7 kcal/mol) were calculated. A simple model is employed to predict reaction efficiencies and branching ratios for these isotope-exchange reactions.
- Barlow,Dang, Thuy Thanh,Bierbaum, Veronica M.
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p. 6832 - 6838
(2007/10/02)
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- NMR VISUALIZATION OF FREE ASPARAGINE IN POTATO TISSUE USING ADDUCT FORMATION WITH FORMALDEHYDE
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The free asparagine in potato (Solanum tuberosum) tuber tissue has been observed by 13C NMR, using labelled formaldehyde as a marker; formaldehyde-asparagine adduct formation is specific and leads to characteristic 13C resonances.In addition, metabolism of formaldehyde to methanol and formate by potato tissue has been observed by 13C and deuterium NMR.Metabolism of formaldehyde-d2 leads to 3 : 1 mixture of CD3OH and CD2HOH.
- Mason, Ralph P.,Sanders, Jeremy K. M.,Gidley, Michael J.
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p. 1567 - 1572
(2007/10/02)
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- Gas-Phase Hydrogen-Deuterium Exchange Reactions of Anions: Kinetics and Detailed Mechanism
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Rate coefficients and branching ratios for anionic hydrogen-deuterium exchange reactions between isotopically labeled hydroxide, amide, hydrogen sulfide, and methoxide ions and their corresponding neutral compounds have been measured in the gas phase by using the selected ion flow tube (SIFT) technique.The kinetic data for the methoxide-methanol systems lead to a determination of the relative base strength of CD3O(1-) and CH3O(1-).The reaction efficiencies and branching ratios of hydroxide-water, amide-ammonia, and amide-water systems are discussed in terms of the mechanism by which exchange occours; the multiply labeled systems reveal that more proton transfer occur than one might expect upon initial inspection of the data.The product distributions are discussed in terms of relative ion-molecule complex lifetimes and dissociation of the complex is competition with scrambling.Efficient H/D exchange was also observed to occur between compounds containing second-row elements and the implications of this are discussed.
- Grabowski, Joseph J.,DePuy, Charles H.,Doren, Jane M.Van,Bierbaum, Veronica, M.
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p. 7384 - 7389
(2007/10/02)
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- Deuterium-Protium Separation Factor between Hydrogen and Liquid Methanols
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The overall deuterium-protium isotope separation factor, α, between hydrogen and the hydroxyl group of liquid methanols containing both CH3 and CD3 substituents has been measured directly between -30 and +64 deg C.The temperature dependence of the respective separation factors is given by the equations ln α(CH3) = -0.4641 + (540.4/T) + (9849.5/T2) and ln α(CD3) = -0.8183 + (708.4/T) - (15263/T2) where T is the absolute temperature.The α values are about 12percent larger than that for liquid water.The equilibrium constants, K1 and K2, for isotopic exchange between hydrogen and the isotopically substituted methanol vapors were calculated from the α values and the corresponding liquid-vapor separation factors αv.At 25 deg C the experimental values of K1 and K2 differ by 7percent, indicating that methyl deuteration exerts a significant secondary isotope effect on deuterium-protium fractionation between methanol vapor and hydrogen.A comparison of equilibrium constants is made with theoretical values calculated from the ratios of partition functions of molecular hydrogen and those derived from the available spectroscopic data of the isotopically substituted methanols.
- Rolston, J.H.,Gale, K.L.
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p. 163 - 167
(2007/10/02)
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