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All total 204 Articles be found
Carbonylation of methyl acetate in the presence of polymeric rhodium-containing catalysts
Kolesnichenko, N. V.,Batov, A. E.,Markova, N. A.,Slivinsky, E. V.
, p. 259 - 262 (2002)
New catalytic systems based on RhCL3 and polymeric nitrogen- and oxygen-containing supports were proposed for the carbonylation of methyl acetate to acetic anhydride. The catalytic systems possess a high activity typical of homogeneous catalysts. The high activity is retained upon the repeated use of the catalyst separated from the reaction products. The nitrogen-containing polymers of the chitosan type serve as cocatalysts. In their presence, the induction period disappears, and the catalytically active species are stabilized, thus enabling the replacement of expensive LiI for cheaper salts of this metal.
Concerted General Acid Catalysis in the Reaction of Acetate Ion with Water-soluble Carbodi-imide
Ibrahim, Ibrahim T.,Williams, Andrew
, p. 25 - 27 (1980)
An intermediate, identified as an O-acetylisourea, is observed spectroscopically in the reaction of a water-soluble carbodi-imide with acetate buffers; a stepwise mechanism for intermediate formation as currently accepted is excluded by the observation of general acid catalysis, while acetate ion attack on carbodi-imide is concerted with proton transfer, and monoanions of dicarboxylic acids react with carbodi-imide with intramolecular concerted proton transfer.
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Adkins,Thompson
, p. 2242 (1949)
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Selectivity Behavior in Hydrocarbonylation of Methyl Acetate Using Homogeneous Rh Complex Catalyst
Kelkar, A. A.,Chaudhari, R. V.
, p. 334 - 343 (1995)
Hydrocarbonylation of methyl acetate using various homogeneous transition metal complex catalysts has been studied.It was observed that Rh(CO)Cl(PPh3)2 was the most active and selective catalyst for ethylidene diacetate synthesis.The effect of the catalyst, methyl acetate, and methyl iodide concentrations; temperature; and partial pressures of CO, H2, and various transition metal complexes as co-catalysts on the selectivity behavior has been studied.Palladium complexes were found to enhance the selectivity of ethylidene diacetate substantially.Catalyst concentration, partial pressures of CO and H2, and temperature also influence the selectivity pattern substantially.On the basis of these results, a possible reaction mechanism is discussed.
Technological features of the reaction of α-tocopherol acetylation
Bulychev
, p. 331 - 332 (1998)
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Kremann,Roesler
, p. 359 (1922)
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TRIOXABICYCLO PENTANE IH PHOTOSENSITIZED OXYGENATION OF 2-DIAZO-3-BUTANONE
Ando, Wataru,Miyazaki, Hajime,Ito, Kenji,Auchi, Daikan
, p. 555 - 556 (1982)
Photosensitized oxygenation of 2-diazo-3-butanone at -78 deg C in CH2Cl2 gave trioxabicyclo pentane which has a long enough life time to allow chemical and spectroscopic characterization.
Adsorption of ethanoic acid on zeolites NaY and HY
Pope, Christopher G.
, p. 3647 - 3651 (1996)
The enthalpy and entropy of adsorption of ethanoic acid by the zeolite HY do not appear to be strongly influenced by the geometric constraints of the pore system. These results, which were predicted previously, contrast with those on H-ZSM-5. A companion examination of adsorption by NaY was complicated by chemical reactions which produced small amounts of ethanoate ions, water, ethanoic anhydride and methane. These products were not observed on HY. The intensity of FTIR absorption bands in the frequency range 1850-1250 cm-1, which resulted from adsorption of ethanoic acid on NaY, depended strongly on adsorbed molecule concentration and were time dependent. Spectra were simpler, and less intense at the same surface concentration on HY.
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Anderson
, p. 2371 (1952)
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FORMATION OF ACETIC ANHYDRIDE BY CARBONYLATION OF METHYL ACETATE
Mamyan, V. A.,Sominskii, S. D.,Pirozhkov, S. D.,Barsegyan, V. L.,Vardanyan, V. D.,Lapidus, A. L.
, p. 2095 - 2098 (1985)
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Mass Spectra and Pyrolyses of Some Vinylene Carbonates
Breitbeil, Fred W.,Skrobot, Angeline A.
, p. 702 - 704 (1982)
The mass spectra of a series of 1,3-dioxol-2-ones were examined for evidence of oxirenes in the fragmentation process.The M-cation radical-CO2 (oxirene or isomers) fragment was observed in six of eight samples.Four major pathways explain the mass spectra: M-cation radical-CO2-CO, M-cation radical-C2O3, M-cation radical-C2O2R and M-cation radical-CO-CO2.Metastable peaks support this.Similar pathways on pyrolysis were sought and observed.At 800 deg C and pressure of 1.5-4 mm, 1,3-dioxol-2-ones 1-3 and 5-7 were pyrolyzed in a stream of helium.The major products were, respectively, ketene (R1=R2=H), propene (R1=R2=CH3), fluorene (R1=R2=C6H5), ethene (R1=H, R2=CH3), stilbene (R1=H, R2=C6H5), and styrene (R1=CH3, R2=C6H5).Apparently the 1,3-dioxol-2-ones lose CO2 and CO successively to produce a carbene which either rearranges or dimerizes.
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Fleming,Philippides
, p. 2426 (1970)
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Ctc-[Pt(NH3)2(cinnamate)(valproate)Cl2] is a highly potent and low-toxic triple action anticancer prodrug
Li, Yang,Shi, Shan,Zhang, Shurong,Gan, Zongjie,Wang, Xin,Zhao, Xudong,Zhu, Yijian,Cao, Meiting,Wang, Xiaoyue,Li, Wei
, p. 11180 - 11188 (2021)
Pt(iv) prodrugs have gained tremendous attention due to their indisputable advantages compared to cisplatin. Herein, new Pt(iv) derivatives with cinnamic acid at the first axial position, and inhibitor of matrix metalloproteinases-2 and-9, histone deacetylase, cyclooxygenase or pyruvate dehydrogenase at the second axial position are constructed to develop multi-action prodrugs. We demonstrate that Pt(iv) prodrugs are reducible and have superior antiproliferative activity with IC50 values at submicromolar concentrations. Notably, Pt(iv) prodrugs exhibit highly potent anti-tumour activity in an in vivo breast cancer model. Our results support the view that a triple-action Pt(iv) prodrug acts via a synergistic mechanism, which involves the effects of CDDP and the effects of axial moieties, thus jointly leading to the death of tumour cells. These findings provide a practical strategy for the rational design of more effective Pt(iv) prodrugs to efficiently kill tumour cells by enhancing their cellular accumulation and tuning their canonical mechanism.
Stromnova, T. A.,Vargaftik, M. N.,Moiseev, I. I.
, (1983)
87. Novel aplysinopsin-type alkaloids from scleractinian corals of the family Dendrophylliidae of the Mediterranean and the Philippines. Configurational-assignment criteria, stereospecific synthesis, and photoisomerization
Guella,Mancini,Zibrowius,Pietra
, p. 773 - 782 (1988)
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Dicarboxylic Acids Link Proton Transfer Across a Liquid Membrane to the Synthesis of Acyl Phosphates. A Model for P-Type H(+)-ATPases
Colton, Ian J.,Kazlauskas, Romas J.
, p. 3626 - 3635 (1994)
H(+)-ATPases are ion pumps that link proton transfer across cell membranes to the synthesis or hydrolysis of ATP.A current research goal is to understand the molecular-level mechanism of this linking.We present a chemical model that mimics some features of H(+)-ATPases by linking proton transfer across a liquid membrane to the synthesis of acyl phosphates using carboxylic acid anhydride intermediates.Citraconic acid (cis-2-methyl-2-butenedioic acid) accelerated the transfer of protons from a pH 0.3 solution across a chloroform liquid membrane to a pH 10 solution.The mechanism involved spontaneous formation of a small amount of citraconic anhydride (0.6percent) in the pH 0.3 layer.This anhydride partitioned into the chloroform layer and diffused to the pH 10 layer, where it hydrolyzed, generating two protons.When the pH 10 layer contained phosphate (1.0 M), some of the citraconic anhydride reacted with phosphate to form citraconyl phosphate, 5.0percent yield.In separate experiments, we confirmed that citraconyl phosphate had high phosphoryl donor potential by reacting it with morpholine to form a phosphoramidate (11.5percent yield) or with fluoride to form fluorophosphonate (32percent yield).To demonstrate the link between an acyl phosphate and a proton gradient in the reverse direction, we used succinyl phosphate, whose hydrolysis occurs in two steps: formation of succinic anhydride, which consumes protons, followed by hydrolysis of succinic anhydride, which releases protons.We generated a pH gradient by carrying out these two steps in separate solutions.Hydrolysis of succinyl phosphate (3.9 mmol) at pH 6.00 started with a increase in pH to 6.16 (0.59 mmol of H(+) consumed) caused by the formation of succinic anhydride.We extracted this anhydride with dichloromethane and transferred it to a separate solution at pH 6.05.Hydrolysis of the anhydride released protons (0.36 mmol), decreasing the pH to 5.23.Our model suggests that H(+)-ATPases could use acyl phosphates and carboxylic acid anhydride intermediates to link proton transfer to ATP synthesis or hydrolysis.
Electrophilic Substitution of Polycyclic Fluoranthene Hydrocarbons
Minabe, Masahiro,Cho, Bongsup P.,Harvey, Ronald G.
, p. 3809 - 3812 (1989)
The first systematic study of the sites of electrophilic substitution (acylation and/or bromination) of polycyclic fluoranthene hydrocarbons is described.The hydrocarbons studied include indenopyrene (1), benzaceanthrylene (2), benzacephenanthrylene (3), and indenochrysene (4).Compounds 1-4 all undergo bromination regioselectively in a single site.The latter are determined by conversion of the bromo derivatives to monodeuterio analogues by metal exchange with butyllithium and analysis of their high-resolution 1H and 13C NMR spectra in comparison with those of the parent hydrocarbons.This method is potentially generally applicable to determination of the sites of substitution of other complex polycyclic hydrocarbon ring systems.Acylation of 1 is shown to take place in the same site as bromination, i.e., the 12-position.For 2 and 4, substitution occurs in the 8- and 5-positions, respectively, in good agreement with theoretical prediction by the DEWAR-PI method based on the relative energies of the Wheland intermediates for substitution at various ring positions.However, for 1 and 3 the principal sites of bromination observed experimentally are the 12- and 1-positions, respectively, which do not accord with theoretical prediction of the 3,5- and 8-positions, respectively.In the latter cases, the observed sites of bromination are only slightly less favorable energetically than the theoretically calculated sites and are probably within the limit of accuracy of the calculations.
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Kirshenbaum et al.
, p. 3141,3143 (1953)
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Linear-reactor-infrared-matrix and Microwave Spectroscopy of the cis-2-Butene Gas-phase Ozonolysis
Kuehne, Heinz,Forster, Martin,Hulliger, Juerg,Ruprecht, Heidi,Bauder, Alfred,Guenthard, Hans-Heinrich
, p. 1971 - 1999 (1980)
Investigation of the formation of complex products in the gas-phase ozonolysis of cis-2-butene by linear-reactor-infrared-matrix and linear-reactor-microwave spectroscopy is reported.The following species have been unequivocally detected: secondary 2-butene ozonide, acetic acid, peracetic acid, glycolaldehyde, dimethyl ketene, the simple mixed anhydrides of formic and acetic acid, 2,3-epoxy-butane and 2-butanone, besides polyatomic products alredy known.In contrast, the primery ozonide has been detectable neither by LR.-MW. nor by LR.-IR.Observation of both stereoisomeric epoxides and kinetic modelling are used to support the intermediate formation of the O'Neal-Blumstein radical CH3CH(O2)CH(O)CH3 and the existence of a reaction channel in which the two carbon atoms of the C,C double bond of the olefin remain connected.As the dominant reaction path a mechanism with a Criegee type split into methyldioxirane (ethylidene peroxide) and acetaldehyde is considered and subsequently proposed to explain formation of many complex products by either unimolecular or bimolecular processes of the peroxide.For the reactions considered, thermochemical estimates of reaction enthalpies and activation data are included.Kinetic modelling for a partial reaction mechanism involving at least two different paths of decay of the O'Neal-Blumstein biradical into Criegee-type intermediates and the 2,3-epoxy-butanes is discussed.
Oxidation of ethyl ether on borate glass: Chemiluminescence, mechanism, and development of a sensitive gas sensor
Hu, Jing,Xu, Kailai,Jia, Yunzhen,Lv, Yi,Li, Yubao,Hou, Xiandeng
, p. 7964 - 7969 (2008)
A gas sensor was developed by using the chemiluminescence (CL) emission from the oxidation of ethyl ether by oxygen in the air on the surface of borate glass. Theoretical calculation, together with experimental investigation, revealed the main CL reactions: ethyl ether is first oxidized to acetaldehyde and then to acetic acid, during which main luminous intermediates such as CH3CO? are generated and emit light with a peak at 493 nm. At a reaction temperature of 245°C, the overall maximal emission was found at around 460 nm, and the linear range of the CL intensity versus the concentration of ethyl ether was 0.12-51.7 μg mL-1 (R = 0.999, n = 7) with a limit of detection (3σ) of 0.04 μg mL-1. Interference from foreign substances including alcohol (methanol, ethanol and isopropanol), acetone, ethyl acetate, n-hexane, cyclohexane, dichloromethane, or ether (n-butyl ether, tetrahydrofuran, propylene oxide, isopropyl ether and methyl tert-butyl ether) was not significant except a minimal signal from n-butyl ether (a simple, sensitive and selective gas sensor for the determination of trace ethyl ether.
Atmospheric chemistry of two biodiesel model compounds: Methyl propionate and ethyl acetate
Andersen, Vibeke F.,Berhanu, Tesfaye A.,Nilsson, Elna J. K.,Jorgensen, Solvejg,Nielsen, Ole John,Wallington, Timothy J.,Johnson, Matthew S.
, p. 8906 - 8919 (2011)
The atmospheric chemistry of two C4H8O2 isomers (methyl propionate and ethyl acetate) was investigated. With relative rate techniques in 980 mbar of air at 293 K the following rate constants were determined: k(C2H5C(O)OCH3 + Cl) = (1.57 ± 0.23) × 10-11, k(C2H5C(O) OCH3 + OH) = (9.25 ± 1.27) × 10-13, k(CH 3C(O)OC2H5 + Cl) = (1.76 ± 0.22) × 10-11, and k(CH3C(O)OC2H5 + OH) = (1.54 ± 0.22) × 10-12 cm3 molecule -1 s-1. The chlorine atom initiated oxidation of methyl propionate in 930 mbar of N2/O2 diluent (with, and without, NOx) gave methyl pyruvate, propionic acid, acetaldehyde, formic acid, and formaldehyde as products. In experiments conducted in N 2 diluent the formation of CH3CHClC(O)OCH3 and CH3CCl2C(O)OCH3 was observed. From the observed product yields we conclude that the branching ratios for reaction of chlorine atoms with the CH3-, -CH2-, and -OCH3 groups are 9 ± 2%, respectively. The chlorine atom initiated oxidation of ethyl acetate in N2/O 2 diluent gave acetic acid, acetic acid anhydride, acetic formic anhydride, formaldehyde, and, in the presence of NOx, PAN. From the yield of these products we conclude that at least 41 ± 6% of the reaction of chlorine atoms with ethyl acetate occurs at the -CH2- group. The rate constants and branching ratios for reactions of OH radicals with methyl propionate and ethyl acetate were investigated theoretically using transition state theory. The stationary points along the oxidation pathways were optimized at the CCSD(T)/cc-pVTZ//BHandHLYP/aug-cc-pVTZ level of theory. The reaction of OH radicals with ethyl acetate was computed to occur essentially exclusively (~99%) at the -CH2- group. In contrast, both methyl groups and the -CH2- group contribute appreciably in the reaction of OH with methyl propionate. Decomposition via the α-ester rearrangement (to give C2H5C(O)OH and a HCO radical) and reaction with O 2 (to give CH3CH2C(O)OC(O)H) are competing atmospheric fates of the alkoxy radical CH3CH2C(O)OCH 2O. Chemical activation of CH3CH2C(O)OCH 2O radicals formed in the reaction of the corresponding peroxy radical with NO favors the α-ester rearrangement.
Ozonolyses of acetylenes revisited
Griesbaum, Karl,Dong, Yuxiang
, p. 575 - 577 (1997)
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Karrer,Hohl
, p. 1933 (1949)
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A transesterification-acetalization catalytic tandem process for the functionalization of glycerol: The pivotal role of isopropenyl acetate
Calmanti, Roberto,Perosa, Alvise,Rigo, Davide,Selva, Maurizio
supporting information, p. 5487 - 5496 (2020/09/23)
At 30 °C, in the presence of Amberlyst-15 as a catalyst, a tandem sequence was implemented by which a pool of innocuous reactants (isopropenyl acetate, acetic acid and acetone) allowed upgrading of glycerol through selective acetylation and acetalization processes. The study provided evidence for the occurrence of multiple concomitant reactions. Isopropenyl acetate acted as a transesterification agent to provide glyceryl esters, and it was concurrently subjected to an acidolysis reaction promoted by AcOH. Both these transformations co-generated acetone which converted glycerol into the corresponding acetals, while acidolysis sourced also acetic anhydride that acted as an acetylation reactant. However, tuning of conditions, mostly by changing the reactant molar ratio and optimizing the reaction time, was successful to steer the set of all reactions towards the synthesis of either a 1?:?1 mixture of acetal acetates (97% of which was solketal acetate) and triacetin, or acetal acetates in up to 91% yield, at complete conversion of glycerol. To the best of our knowledge, a one-pot protocol with such a degree of control on the functionalization of glycerol via transesterification and acetalization reactions has not been previously reported. The procedure was also easily reproduced on a gram scale, thereby proving its efficiency for preparative purposes. Finally, the design of experiments with isotopically labelled reagents, particularly d4-acetic acid and d6-acetone, helped to estimate the contribution of different reaction partners (iPAc/AcOH/acetone) to the formation of final products. This journal is
Production of acetic anhydride
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Paragraph 0067-0069, (2017/06/27)
An object is to provide a method for producing a ketene derivative that decreases the consumption quantity of phosphorus compounds, and the discharge quantity of the phosphorus compounds into the environment. A method for producing a ketene derivative includes a step (i) of conducting thermal decomposition reaction of acetic acid in a presence of a phosphorus-containing catalyst in a reactor to produce a thermal decomposition gas containing ketene, a step (ii) of cooling the thermal decomposition gas to be separated into a gaseous component containing ketene, and a condensed liquid containing a phosphorus compound (a), and a step (iii) of causing the ketene to react with a different organic compound to produce a ketene derivative. The step (i) includes conducting the thermal decomposition reaction while supplying, into the reactor, the condensed liquid containing the phosphorus compound (a) or a concentrated liquid of the condensed liquid.