F+:Highly flammable;
75-07-0Relevant articles and documents
Palladium-Copper-exchanged Y Type Zeolites: A True Heterogeneous Wacker Catalyst
Espeel, P. H.,Tielen, M. C.,Jacobs, P. A.
, p. 669 - 671 (1991)
Evidence is presented that faujasite-type zeolites with specific Si:Al framework ratios exchanged with Pd(NH3)42+ and Cu2+, catalyse the oxidation of ethylene into acetaldehyde, in exactly the same way as the homogeneous Wacker system II and CuII in concentrated chloride solution>; the active centre is found to be a partially ammoniated PdII ion, most probably PdII(NH3)2, which itself belongs to an electron transfer chain consisting of the alkene reagent, the faujasite encaged PdII/Pd0 and CuII/CuI redox couples and dioxygen.
Mechanism of uncatalyzed and osmium(VIII) catalyzed oxidation of L-alanine by Copper(III) periodate complex in aqueous alkaline medium
Lamani, Shekappa D.,Veeresh, Tegginamat M.,Nandibewoor, Sharanappa T.
, p. 394 - 404 (2011)
The kinetics of oxidation of the L-alanine (L-ala) by diperiodatocuprate(III) (DPC) was carried both in the absence and presence of osmium(VIII) catalyst in alkalinemedium at constant ionic strength of 0.01 mol dm-3 spectrophotometrically.The involvement of free radicals was observed in both the reactions. The oxidation products in both the cases were acetaldehyde and Cu(II), identified by spot test and spectroscopic studies. The stoichiometry is the same in both cases; that is, [L-ala]:[DPC] = 1:2. The reaction was first order in [DPC] and has negative fractional order in [OH-] in both the catalyzed and uncatalyzed cases. The order in [osmium(VIII)] was unity. A mechanism involving the formation of a complex between L-ala and DPC in case of uncatalyzed reaction and a mechanism involving the formation of a complex between L-alanine and osmium(VIII) in case of catalyzed reaction were proposed. The reaction constants involved in the different steps of the mechanisms were calculated for both reactions. The catalytic constant (Kc) was also calculated for catalyzed reaction at different temperatures. The activation parameters with respect to slow step of themechanisms were computed and discussed for both the cases. The thermodynamic quantities were also determined for uncatalyzed and catalyzed reactions. Copyright Taylor & Francis Group, LLC.
Kinetics and Thermochemistry of the CH3CO Radical: Study of the CH3CO + HBr --> CH3CHO + Br Reaction
Niiranen, Jukka T.,Gutman, David,Krasnoperov, Lev N.
, p. 5881 - 5886 (1992)
The kinetics of the reaction between CH3CO and HBr has been studied using a heatable tubular reactor coupled to a photoionization mass spectrometer.CH3CO was produced homogeneously by laser photolysis in the presence and absence of HBr.Radical decays were monitored in time-resolved experiments.Rate constants were determined at five temperatures in the range 300-400 K and fitted to the Arrhenius expression, 6.4 (+/-3.6) * 10-13 exp-1/RT> cm3 molecule-1 s-1.This kinetic information was combined with known rate constants andArrhenius parameters for the reverse reaction to obtain the heat of formation of CH3CO.Both second law and third law procedures were used to obtain this thermochemical information from these rate constants.The two determinations of this heat of formation were in close agreement (differing by only 0.4 kJ mol-1).These results, taken together, provide a CH3CO heat of formation of -10.0 +/- 1.2 kJ mol-1 at 298 K which is 14 kJ mol-1 higher than the value in common use.The current results imply a CH3-CO bond enthalpy of 45.1 (+/-1.5) kJ mol-1 which is 14 kJ mol-1 lower than currently believed and a CH3CO-H bond enthalpy of 373.8 (+/-1.5) kJ mol-1 which is higher by this same figure.Former disparities between reported CH3CO heats of formation associated with the equilibrium systems studied to obtain this thermochemical information are resolved.
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Patterson,Day
, p. 1276 (1934)
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Kinetics of acid-catalyzed hydration of acetylene. Evidence for the presence in the solution phase of unsubstituted vinyl cation
Lucchini, Vittorio,Modena, Giorgio
, p. 6291 - 6296 (1990)
The rates of acetylene hydration in the convenient range of aqueous sulfuric acid (and those of propyne, tert-butylacetylene, ethylene, propene, and tert-butylethylene, for comparative purposes) have been measured at 25 °C with an NMR technique. The correlation of the kinetic data with the excess acidity function X gives a value of 1.12 for the slope parameter m*, which suggests that the intermediate is protonated acetylene, C2H3+ (probably as vinyl cation 3 rather than as hydrogen-bridged ion 4). The comparison with the m* value for the hydration of ethylene (1.50) indicates that protonated acetylene possesses stronger susceptibility to solvation than ethylium ion C2H5+. The deuteration patterns in the products (acetaldehyde and crotonaldehyde) obtained in deuteriosulfuric acid rule out the reversibility of the protonation process and also the conversion between 3 and 4.
Reaction of Catalase with Ethylhydrogen Peroxide
Kremer, Mordechai L.
, p. 91 - 104 (1985)
C2H5OOH reacts with catalase in a basically irreversible reaction in the course of which the species called compound (I) is formed and decomposed.The formation of compound (I) is preceded by the formation of a precursor complex which is able to react with a further molecule of C2H5OOH to yield an inactive biperoxy complex.The biperoxy complex causes a diminution of the extent of formation of compound (I) at high .As a consequence, compound (I) can never be formed quantitatively.Some of its physical constants can, nevertheless, be evaluated.Compound (I) with C2H5OOH appears to retrain C2H5OH in its structure.
Highly efficient catalyst for the decarbonylation of lactic acid to acetaldehyde
Katryniok, Benjamin,Paul, Sebastien,Dumeignil, Franck
, p. 1910 - 1913 (2010)
The gas phase decarbonylation of lactic acid was performed over various silica-supported heteropolyacids. The obtained performances were, by far, higher than those previously described in the literature. In particular, the best results were obtained for silicotungstic acid-based catalysts, which showed very high yields of acetaldehyde (81-83%) at high lactic acid conversion (up to 91%). The Royal Society of Chemistry 2010.
Single-turnover studies on brewer's yeast pyruvate decarboxylase: C(2)-proton transfer from thiamin diphosphate
Crane III, Edward J.,Vaccaro, Joseph A.,Washabaugh, Michael W.
, p. 8912 - 8917 (1993)
Rate constants for formation of acetaldehyde from pyruvate catalyzed by the thiamin diphosphate (TDP)-dependent enzyme pyruvate decarboxylase (PDC; EC 4.1.1.1) from Saccharomyces carlsbergensis were determined under single-turnover conditions at 30°C in 100 mM sodium 2-(N-morpholino)ethanesulfonate buffer (pH 6.00) containing 100 mM pyruvamide, 10 mM MgSO4, and 12.5 μM sodium pyruvate. Observed rate constants in the range kobsd = 2.5-6.7 s-1 for 33-104 μM (8-15 mg mL-1) pyruvamide-activated PDC agree with values of kobsd calculated by numerical integration with microscopic rate constants derived previously from steady-state kinetic isotope effects. The observed rate constant kobsd = 6.7 ± 0.4 s-1 is independent of the concentration of pyruvamide-activated PDC in the range 104-150 μM. The decrease in the concentration dependence of the observed rate constants at > 104 μM PDC is consistent with either a change in rate-limiting step or complex formation involving the reactants. There is little or no primary kinetic isotope effect, (kH/kD)obsd ≤ 1.2, for C(2)-hydron exchange from PDC-bound TDP for 33-104 μM pyruvamide-activated PDC. This provides evidence against rate-limiting C(2)-proton transfer between C(2)-H in PDC-bound TDP and a catalytic base with -7 ≤ ΔpKa (= pKaBH - pKaC(2)H) ≤ 7 to form a discrete ylide intermediate during catalysis by PDC.
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Evnin et al.
, p. 109,111,115,117 (1973)
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The Dehydrogenation of Ethanol in Dilute Aqueous Solution Photosensitised by Benzophenones
Green, Peter,Green, William A.,Harriman, Anthony,Richoux, Marie-Claude,Neta, Pedatsur
, p. 2109 - 2128 (1988)
The photochemical properties of a series of water-soluble benzophenones have been evaluated in dilute aqueous solution.The compounds possess lowest-energy singlet and triplet excited states demonstrating considerable n,?* character.As such, irradiation of the compounds in aqueous solution containing ethanol (2percent v/v) results in pinacol formation via a triplet-state hydrogen-abstraction process.In the presence of a colloidal Pt catalyst, the intermediate ketyl and 1-hydroxyethyl radicals can be used to reduce water to H2.The rate of H2 formation and its total yield depend upon the nature of the substituent used to solubilise the benzophenone.The rate at which the ketyl radical transfers an electron to the Pt particles can be rationalised in terms of thermodynamic and electrostatic factors.
Oxidation of threonylmethionine by peroxynitrite. Quantification of the one-electron transfer pathway by comparison to one-electron photooxidation
Jensen, Jana L.,Miller, Brian L.,Zhang, Xiaoping,Hug, Gordon L.,Sch?neich, Christian
, p. 4749 - 4757 (1997)
Peroxynitrite can modify methionine by one- and two-electron oxidation pathways. Here, we have quantified the extent of one-electron oxidation of threonylmethionine (Thr-Met) by peroxynitrite using a characteristic reaction according to which Thr-Met sulfur radical cations decompose via fragmentation of the Thr side chain, yielding acetaldehyde. The efficiencies, f(acet, photo) for the formation of acetaldehyde from Thr-Met sulfur radical cations were obtained by means of one-electron photooxidation using triplet 4- carboxybenzophenone. Exact quantum yields for the formation of Thr-Met sulfur radical cations by triplet 4-carboxybenzophenone were obtained by laser flash photolysis and time-resolved UV spectroscopy. Acetaldehyde yields were measured for the reaction of peroxynitrite with Thr-Met, and division of these acetaldehyde yields by f(acet, photo) yielded the extents to which peroxynitrite reacted with Thr-Met via the one-electron transfer pathway. There was little one-electron oxidation of Thr-Met by peroxynitrite at pH 7.4, i.e., 1.5%, 1.8%, and 5.3% based on the total chemical conversion of Thr-Met for Thr-Met concentrations of 1 x 10-3, 5 x 10-4, and 1.75 x 10- 4 M, respectively. In all cases the major reaction product was the two- electron oxidation product threonylmethionine sulfoxide. However, at pH 6.0, one-electron oxidation of Thr-Met showed a significantly higher efficiency of 14% for [Thr-Met] = 1.75 x 10-4 M. Under all experimental conditions the extent of one-electron oxidation increased with decreasing peptide concentration in agreement with a recently established mechanism according to which the one-electron oxidation of Met by peroxynitrite requires a unimolecular transformation of peroxynitrous acid to an excited species which is the ultimate one-electron oxidant.
Zur Acetalbildung aus Alkoholen und Acetylen mit Platin- und Palladiumverbindungen als Katalysator
Steinborn, Dirk,Nuenthel, Ralph,Krause, Katrin
, p. C54 - C58 (1991)
The platinum and palladium catalyzed addition of alcohols to acetylene to give acetals was investigated.The catalytic activity and productivity in dependence on the platinum compound and alcohol used, on the oxidation state of platinum and the cocatalytic effect of HCl are discussed.Systems of the type X2/HX (X = ClO4-, BF4-) are introduced as the first catalytically active palladium-containing systems.
Kinetic Studies of Secondary Alcohol Photo-oxidation on ZnO and TiO2 at 348 K Studied by Gas-chromatographic Analysis
Cunningham, Joseph,Hodnett, Benjamin K.
, p. 2777 - 2802 (1981)
Kinetics of conversion of propan-2-ol and butan-2-ol to the corresponding ketones by photoassisted dehydrogenation, (-H2)*, to lower aldehydes by a photoassisted Cα-Cβ bond cleavage process, (α-β)*, and to trace quantities of alkene by photoassisted dehydration (-H2O)* have been investigated at oxygen partial pressures in the range 0-700 Torr and at alcohol partial pressures of 0-60 Torr, utilising dynamic flow photoreactors and gas-chromatographic analysis.Qualitatively similar results were obtained either with a 'continuous reactant flow plus continuous u.v. illumination' procedure allied to intermittent sampling, or with a 'pulsed reactant and analysis' procedure.Both procedures yielded dependence upon alcohol pressure indicative of two parallel photoassisted pathways to (-H2)* product, one being Langmuir-Hinshelwood (LH*) and the other Eley-Rideal (ER*) in character.A decline in activity of the metal oxide surfaces as photoassisted conversion of alcohol increased was observed with both procedures and affected the LH* process for (-H2)* more strongly.It is proposed that this LH* process involved alcohol chemisorption and hole localisation at coordinatively unsaturated O2-cus ions.The ER* process is envisaged to have involved encounter of alcohol (from the gas phase or from a reversibly adsorbed weakly bound state) with a much more numerous type of surface location capable of being photoactivated by hole capture.The proposed mechanisms account for observed dependences of the (-H2)* process upon square root of the incident light intensity, upon alcohol pressure and upon oxygen pressure.
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Kanoh et al.
, p. 372,377 (1979)
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Cohen
, p. 141 (1920)
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Translational energy of products in the K + CH3COCl KCl + CH3CO reaction
Pauluth, M.,Rotzoll, G.
, p. 1515 - 1516 (1984)
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Bernardini,Cherniak
, p. 1371 (1973)
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Piria, R.
, p. 126 - 132 (1856)
Catalytic dehydration of lactic acid to acrylic acid using calcium hydroxyapatite catalysts
Ghantani, Vidhya C.,Lomate, Samadhan T.,Dongare, Mohan K.,Umbarkar, Shubhangi B.
, p. 1211 - 1217 (2013)
A series of calcium hydroxyapatite (HAP) catalysts were synthesised with a Ca/P ratio ranging from 1.3 to 1.89 by a co-precipitation method that involved changing the pH of the calcium and phosphorous precursors. The physicochemical characterization by XRD, SEM, BET surface area and CO2 and NH 3-TPD techniques confirmed the hydroxyapatite formation. These HAP catalysts were used for the vapour phase dehydration of lactic acid to acrylic acid. The HAP catalyst with a Ca/P ratio of 1.3 was found to be the most efficient catalyst among the synthesised series, which gave 100% conversion of lactic acid and 60% selectivity towards acrylic acid at 375 °C when a 50% (w/w) aqueous solution of lactic acid was used. The higher selectivity towards acrylic acid has been correlated to the increased acidity and reduced basicity of the HAP catalyst with a Ca/P ratio of 1.3 compared to the other HAP catalysts. The catalyst was found to be very stable and no deactivation was observed even after 300 h of reaction time. In situ FTIR studies were performed for understanding the mechanistic aspects and showed the formation of calcium lactate as an intermediate species during the dehydration of lactic acid to acrylic acid.
Ethanol steam reforming over Rh and Pt catalysts: Effect of temperature and catalyst deactivation
Bilal, Muhammad,Jackson, S. David
, p. 754 - 766 (2013)
In this study 0.2% Rh/alumina and 0.2% Pt/alumina catalysts were tested for ethanol steam reforming (ESR) over a range of temperatures (773-873 K) at 20 barg with a 5:1 steam to ethanol ratio. Hydrogen was always the main product over Rh/Al2O3 although liquid products such as acetaldehyde, diethyl ether and acetone were also produced (2O3 also produced hydrogen as the main product but at 773 K significant levels of ethene were formed. Less liquid product was formed over the Pt/Al2O3 (-1) however the platinum catalyst gave a low activation energy more typical of a diffusion controlled system (～20 kJ mol-1). At 873 K the platinum catalyst is more active (90% conversion cf. ～60%) and gives a higher hydrogen selectivity (55% cf. 49%) than the rhodium catalyst. Temperature-programmed oxidation (TPO), Raman spectroscopy, BET and SEM analysis were used to characterise the nature of the coke species for reactions at 773 K, 823 K and 873 K. The TPO results indicated that different types of coke were deposited on both catalysts during ESR. Carbon nanotubes and filamentous coke were observed on the catalysts after ESR at 873 K. Raman analysis revealed that the coke deposited on the catalysts was graphitic in nature and the disorder in the graphitic type coke generally increased with an increase in the reaction temperature.
Identification of a hypothetical protein from podospora anserina as a nitroalkane oxidase
Tormos, Jose R.,Taylor, Alexander B.,Daubner, S. Colette,Hart, P. John,Fitzpatrick, Paul F.
, p. 5035 - 5041 (2010)
The flavoprotein nitroalkane oxidase (NAO) from Fusarium oxysporum catalyzes the oxidation of primary and secondary nitroalkanes to their respective aldehydes and ketones. Structurally, the enzyme is a member of the acyl-CoA dehydrogenase superfamily. To date no enzymes other than that from F. oxysporum have been annotated as NAOs. To identify additional potential NAOs, the available database was searched for enzymes in which the active site residues Asp402, Arg409, and Ser276 were conserved. Of the several fungal enzymes identified in this fashion, PODANSg2158 from Podospora anserina was selected for expression and characterization. The recombinant enzyme is a flavoprotein with activity on nitroalkanes comparable to the F. oxysporum NAO, although the substrate specificity is somewhat different. Asp399, Arg406, and Ser273 in PODANSg2158 correspond to the active site triad in F. oxysporum NAO. The kcat/KM-pH profile with nitroethane shows a pK a of 5.9 that is assigned to Asp399 as the active site base. Mutation of Asp399 to asparagine decreases the kcat/KM value for nitroethane over 2 orders of magnitude. The R406K and S373A mutations decrease this kinetic parameter by 64- and 3-fold, respectively. The structure of PODANSg2158 has been determined at a resolution of 2.0 A, confirming its identification as an NAO.
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Polishchuk et al.
, (1971)
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Effect of ascorbic acid and its derivatives on the radiation-induced transformations of oxygenated ethanol and its aqueous solutions
Brinkevich
, (2015)
Upon irradiation ascorbic acid and 5,6-O-isopropylidene-2,3-O-dimethylascorbic acid are capable of lowering the yields of the main products of γ-radiolysis of oxygen-saturated ethanol or its aqueous solutions at pH 7 by virtue of reduction of peroxyl radi
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De Graff,Le Fevre
, p. 315 (1925)
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v. Lebedew,Polonski
, (1923)
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Binary Au–Cu Reaction Sites Decorated ZnO for Selective Methane Oxidation to C1 Oxygenates with Nearly 100% Selectivity at Room Temperature
Gong, Zhuyu,Liu, Huifen,Luo, Lei,Ma, Jiani,Tang, Junwang,Xing, Jialiang,Xu, Youxun
supporting information, p. 740 - 750 (2022/01/03)
Direct and efficient oxidation of methane to methanol and the related liquid oxygenates provides a promising pathway for sustainable chemical industry, while still remaining an ongoing challenge owing to the dilemma between methane activation and overoxidation. Here, ZnO with highly dispersed dual Au and Cu species as cocatalysts enables efficient and selective photocatalytic conversion of methane to methanol and one-carbon (C1) oxygenates using O2 as the oxidant operated at ambient temperature. The optimized AuCu–ZnO photocatalyst achieves up to 11225 μmol·g–1·h–1 of primary products (CH3OH and CH3OOH) and HCHO with a nearly 100% selectivity, resulting in a 14.1% apparent quantum yield at 365 nm, much higher than the previous best photocatalysts reported for methane conversion to oxygenates. In situ EPR and XPS disclose that Cu species serve as photoinduced electron mediators to promote O2 activation to ?OOH, and simultaneously that Au is an efficient hole acceptor to enhance H2O oxidation to ?OH, thus synergistically promoting charge separation and methane transformation. This work highlights the significances of co-modification with suitable dual cocatalysts on simultaneous regulation of activity and selectivity.
Photophysics of Perylene Diimide Dianions and Their Application in Photoredox Catalysis
Li, Han,Wenger, Oliver S.
supporting information, (2021/12/23)
The two-electron reduced forms of perylene diimides (PDIs) are luminescent closed-shell species whose photochemical properties seem underexplored. Our proof-of-concept study demonstrates that straightforward (single) excitation of PDI dianions with green
Dual utility of a single diphosphine-ruthenium complex: A precursor for new complexes and, a pre-catalyst for transfer-hydrogenation and Oppenauer oxidation
Mukherjee, Aparajita,Bhattacharya, Samaresh
, p. 15617 - 15631 (2021/05/19)
The diphosphine-ruthenium complex, [Ru(dppbz)(CO)2Cl2] (dppbz = 1,2-bis(diphenylphosphino)benzene), where the two carbonyls are mutually cis and the two chlorides are trans, has been found to serve as an efficient precursor for the synthesis of new complexes. In [Ru(dppbz)(CO)2Cl2] one of the two carbonyls undergoes facile displacement by neutral monodentate ligands (L) to afford complexes of the type [Ru(dppbz)(CO)(L)Cl2] (L = acetonitrile, 4-picoline and dimethyl sulfoxide). Both the carbonyls in [Ru(dppbz)(CO)2Cl2] are displaced on reaction with another equivalent of dppbz to afford [Ru(dppbz)2Cl2]. The two carbonyls and the two chlorides in [Ru(dppbz)(CO)2Cl2] could be displaced together by chelating mono-anionic bidentate ligands, viz. anions derived from 8-hydroxyquinoline (Hq) and 2-picolinic acid (Hpic) via loss of a proton, to afford the mixed-tris complexes [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], respectively. The molecular structures of four selected complexes, viz. [Ru(dppbz)(CO)(dmso)Cl2], [Ru(dppbz)2Cl2], [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], have been determined by X-ray crystallography. In dichloromethane solution, all the complexes show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry on the complexes shows redox responses within 0.71 to -1.24 V vs. SCE. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic transfer-hydrogenation and Oppenauer oxidation.
