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41.
CO(2)-expanded solvents: unique and versatile media for performing homogeneous catalytic oxidations 总被引:2,自引:0,他引:2
Wei M Musie GT Busch DH Subramaniam B 《Journal of the American Chemical Society》2002,124(11):2513-2517
The work summarized here demonstrates a new concept for exploiting dense phase CO(2), media considered to be "green" solvents, for homogeneous catalytic oxidation reactions. According to this concept, the conventional organic solvent medium used in catalytic chemical reactions is replaced substantially (up to 80 vol %) by CO(2), at moderate pressures (tens of bars), to create a continuum of CO(2)-expanded solvent media. A particular benefit is found for oxidation catalysis; the presence of CO(2) in the mixed medium increases the O(2) solubility by ca. 100 times compared to that in the neat organic solvent while the retained organic solvent serves an essential role by solubilizing the transition metal catalyst. We show that CO(2)-expanded solvents provide optimal properties for maximizing oxidation rates that are typically 1-2 orders of magnitude greater than those obtained with either the neat organic solvent or supercritical CO(2) as the reaction medium. These advantages are demonstrated with examples of homogeneous oxidations of a substituted phenol and of cyclohexene by molecular O(2) using transition metal catalysts, cobalt Schiff-base and iron porphyrin complexes, respectively, in CO(2)-expanded CH(3)CN. 相似文献
42.
Kailash C. Malhotra Brij Bala Neeraj Sharma Subhash C. Chaudhry 《Transition Metal Chemistry》1995,20(4):388-390
Summary Complexes of composition [VOCl2(OC6H4Bu-t-4)] (1) and [VOCl(OC6H4Bu-t-4)2] (2) have been synthesized by the reaction of VOCl3 with equimolar and bimolar amounts, respectively, of 4-t-BuC6H4OSiMe3 in CCl4 and characterized by physio-chemical techniques. The complexes react with -hydroxyaldehydes and ketones such as 2-hydroxybenzaldehyde (salicylaldehyde, salH), and 2-hydroxy-2-phenylacetophenone (benzoin, benzH), 2-hydroxyacetophenone (hapH) and also with the potassium salt of p-chlorobenzohydroxamic acid (KBHACl) in 11 and 12 molar ratios, to yield five- and six-coordinate complexes. 相似文献
43.
Biosensors designed for environmental and food quality control based on screen-printed graphite electrodes with different configurations 总被引:3,自引:0,他引:3
Avramescu A Andreescu S Noguer T Bala C Andreescu D Marty JL 《Analytical and bioanalytical chemistry》2002,374(1):25-32
Graphite electrodes fabricated by screen-printing have been used as amperometric detectors in biosensors based on NAD(+)-dependent dehydrogenases, tyrosinase, or genetically modified acetylcholinesterases. The mono-enzyme sensors have been optimized as disposable or reusable devices for detection of a variety of substrates important in the food industry ( D-lactic acid, L-lactic acid, acetaldehyde) or in environmental pollution control (phenols and dithiocarbamate, carbamate and organophosphorus pesticides). The sensors were prepared in four configurations differing in enzyme confinement, enzyme immobilization and location of the immobilization agent in the biosensor assembly. Tests on real samples have been performed with the biosensors; D-lactic acid and acetaldehyde have been detected in wine and phenols in air. 相似文献
44.
Yun J. Lee Jason R. King Bala Chandra Chenna Samuel B. OwensJr. Jason L. Freeman Gary M. Gray Sadanandan E. Velu 《Journal of chemical crystallography》2009,39(12):902-907
Abstract
Details of the synthesis and crystal structure determination of (E)-2-(7-(3-(thiophen-2-yl)acrylamido)-2,3-dihydro-5-oxobenzo[e][1,4]oxazepin-1(5H)-yl)ethyl acetate are presented. The compound crystallizes in the triclinic P−1 space group (a = 8.3377(17), b = 9.792(2), c = 12.469(3) ?, α = 96.39(3)°, β = 108.50(3)°, γ = 97.68(3)°, V = 943.9(3) ?3, Z = 2). Interesting features of the structure include intermolecular hydrogen bonding between the amide proton on one molecule and the carbonyl oxygen of the dihydrooxazepinone ring on an adjacent molecule, the boat conformation of the dihydrooxazepinone ring, and π-π stacking between thiophene and phenyl rings on adjacent molecules with a distance between centroids of 3.79(2) ?. 相似文献45.
Bala Chandra Chenna Bidhan A. Shinkre Shweta Patel Samuel B. OwensJr. Gary M. Gray Sadanandan E. Velu 《Journal of chemical crystallography》2008,38(3):189-194
Abstract Synthesis, separation and X-ray crystal structures of E and Z isomers of 3-(2,5-dimethoxyphenyl)-2-(4-methoxyphenyl)acrylic acid are reported. Separation of E and Z isomers from a 1:1 mixture has been carried out by selective acidification of their sodium salts carefully controlling the
pH of the solution. The structures of E and Z isomers were confirmed by determining crystal structures of these isomers using single crystal X-ray diffraction. The E isomer crystallizes in the P21/c space group with a = 11.493(2) ?, b = 5.5456(11) ?, c = 24.900(5) ?, α = 90°, β = 92.36(3)°, γ = 90°, Z = 4. The Z isomer crystallizes in the P21/c space group with a = 10.192(2) ?, b = 12.893(3) ?, c = 13.948(3) ?, α = 90°, β = 92.18(3)°, γ = 90°, Z = 4. Details of the synthesis and structural characterization and X-ray crystal structure determination of the title compounds
are presented.
Index Abstract
Synthesis, Separation and Crystal Structures of
E
and
Z
Isomers of 3-(2,5-Dimethoxyphenyl)-2-(4-Methoxyphenyl)Acrylic Acid
Balachandra Chenna, Bidhan A. Shinkre, Shweta Patel, Samuel B. Owens Jr., Gary M. Gray, Sadanandan E. Velu*
Separation of E and Z isomers of 3-(2,5-dimethoxyphenyl)-2-(4-methoxyphenyl)acrylic acid from a 1:1 mixture has been carried out by selective acidification
of their sodium salts and the structures of the individual isomers have been determined by X-ray single crystal diffraction.
相似文献
46.
Raj?Pal?SharmaEmail author Rajni?Sharma Ritu?Bala Paloth?Venugopalan 《Journal of chemical crystallography》2005,35(8):595-601
The title compound was synthesized by mixing the separately dissolved trans-dichlorobis(ethylenediamine)cobalt(III) chloride and sodium 4-aminobenzoate in aqueous medium in 1:3 molar ratio and recrystallizing the product obtained, from hot water. Elemental analyses and spectroscopic techniques (IR, UV/visible, 1H and 13C NMR) were used for characterizing the complex salt. X-ray structure determination revealed an ionic structure consisting of [Co(en)2(C7H6NO2)2]+ cation, (C7H6NO2)− anion and four lattice water molecules. The complex salt crystallizes in the triclinic space group P
with cell dimensions a = 9.985(1) Å, b = 11.522(1) Å, c = 14.233(1) Å, α = 80.20(1)∘, β = 72.80(1)∘, γ = 86.43(1)∘, Z = 2, V = 1541.3(2) Å3, R1 = 0.0291, and wR2 = 0.0751. 相似文献
47.
Indu Bala 《Liquid crystals》2016,43(7):963-971
A facile synthesis of a novel covalently linked disc–rod mesogen is reported consisting of a truxene-based core attached to which are six 4-cyanobiphenyl units via flexible alkyl spacers. The compound formed a stable Langmuir monolayer at the air–water interface. The atomic force microscope study on the Langmuir–Blodgett film of the molecule reveals a tilted orientation at air–solid interfaces. 相似文献
48.
Using a one-pot synthetic approach, a single isomer of bis(diethylenetriamine)cobalt(III) cation, [Co(dien)2]3+ is obtained in bulk from the isomeric mixture (s-fac : u-fac : mer is 7 : 28 : 65) using sodium salts of benzoates (BBz-bromobenzoate, DNBz-dinitrobenzoate, MBz-methylbenzoate) in aqueous medium. Herein, we report the syntheses and characterization of three complexes of composition mer-[Co(dien)2]Cl(p-BBz)2·H2O (1), s-fac-[Co(dien)2](o,p-DNBz)3·H2O (2) and mer-[Co(dien)2]Cl(p-MBz)2·4H2O (3) in the continuation of our earlier work, where benzoate (Bz), p-chlorobenzoate (CBz), p-nitrobenzoate (NBz) and p-aminobenzoate (ABz) were used. The isomeric identification of complex cation was initially made on the basis of spectroscopic characterization (UV–visible, IR and NMR). The binding properties of [Co(dien)2]3+ with benzoates (p-BBz, o,p-DNBz, p-MBz, Bz, CBz, NBz or ABz) have been studied using standard UV–visible spectroscopic titrations in aqueous medium and comparison indicate ion association constants of s-fac > mer. The single-crystal X-ray diffraction structure analysis of 3 reveals the presence of discrete ions ([Co(dien)2]3+, chloride, p-MBz) along with four lattice water molecules. The structure of 3, with formula [Co(dien)2](p-MBz)2Cl·4H2O, consists of alternating layers made of benzoate ions and layers made of [Co(dien)2]3+, chloride and water molecules. These layers result in the formation of their respective columns and intermolecular cohesion of p-MBz within the columns of [Co(dien)2]3+ is achieved via electrostatic and H-bonding interactions. 相似文献
49.
Hashmi S. A. Bhat Md Yasir Singh Manoj K. Sundaram N. T. Kalyana Raghupathy Bala P. C. Tanaka Hideaki 《Journal of Solid State Electrochemistry》2016,20(10):2817-2826
Journal of Solid State Electrochemistry - We report the studies on composite gel polymer electrolytes (GPEs) comprising 0.5 M solution of sodium trifluoromethane sulfonate (Na-triflate or... 相似文献
50.
Kurt M. Bretthauer Bala Shetty Siddhartha Syam 《The Journal of the Operational Research Society》1996,47(3):457-462
In this paper we present a new branch and bound algorithm for solving a class of integer quadratic knapsack problems. A previously published algorithm solves the continuous variable subproblems in the branch and bound tree by performing a binary search over the breakpoints of a piecewise linear equation resulting from the Kuhn-Tucker conditions. Here, we first present modifications to a projection method for solving the continuous subproblems. Then we implement the modified projection method in a branch and bound framework and report computational results indicating that the new branch and bound algorithm is superior to the earlier method. 相似文献