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.
Catalytic dehydration of lactic acid to acrylic acid over dibarium pyrophosphate
Tang, Congming,Peng, Jiansheng,Fan, Guoce,Li, Xinli,Pu, Xiaoli,Bai, Wei
, p. 231 - 234 (2014)
Barium phosphate catalysts were prepared by a precipitation method. The catalysts were calcined at 500 C for 6 h in air atmosphere and characterized by SEM for morphological features, by XRD for crystal phases, by N2 sorption for specific surface area, by TPD-NH3 for acidity and by TG for thermal stability. The dibarium pyrophosphate catalyst was found to have the best catalytic performance, ascribing to weak acidity on the surface. Under the optimal reaction conditions, 99.7% of the lactic acid conversion and 76.0% of the selectivity to acrylic acid were achieved over the dibarium pyrophosphate catalyst.
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.
Photochemical redox reactions of copper(II)-alanine complexes in aqueous solutions
Lin, Chen-Jui,Hsu, Chao-Sheng,Wang, Po-Yen,Lin, Yi-Liang,Lo, Yu-Shiu,Wu, Chien-Hou
, p. 4934 - 4943 (2014)
The photochemical redox reactions of Cu(II)/alanine complexes have been studied in deaerated solutions over an extensive range of pH, Cu(II) concentration, and alanine concentration. Under irradiation, the ligand-to-metal charge transfer results in the reduction of Cu(II) to Cu(I) and the concomitant oxidation of alanine, which produces ammonia and acetaldehyde. Molar absorptivities and quantum yields of photoproducts for Cu(II)/alanine complexes at 313 nm are characterized mainly with the equilibrium Cu(II) speciation where the presence of simultaneously existing Cu(II) species is taken into account. By applying regression analysis, individual Cu(I) quantum yields are determined to be 0.094 ± 0.014 for the 1:1 complex (CuL) and 0.064 ± 0.012 for the 1:2 complex (CuL2). Individual quantum yields of ammonia are 0.055 ± 0.007 for CuL and 0.036 ± 0.005 for CuL2. Individual quantum yields of acetaldehyde are 0.030 ± 0.007 for CuL and 0.024 ± 0.007 for CuL2. CuL always has larger quantum yields than CuL2, which can be attributed to the Cu(II) stabilizing effect of the second ligand. For both CuL and CuL2, the individual quantum yields of Cu(I), ammonia, and acetaldehyde are in the ratio of 1.8:1:0.7. A reaction mechanism for the formation of the observed photoproducts is proposed.
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.
Kinetic evidence for an anion binding pocket in the active site of nitronate monooxygenase
Francis, Kevin,Gadda, Giovanni
, p. 167 - 172 (2009)
A series of monovalent, inorganic anions and aliphatic aldehydes were tested as inhibitors for Hansenula mrakii and Neurospora crassa nitronate monooxygenase, formerly known as 2-nitropropane dioxygenase, to investigate the structural features that contri
Catalytic power of pyruvate decarboxylase. Rate-limiting events and microscopic rate constants from primary carbon and secondary hydrogen isotope effects
Alvarez, Francisco J.,Ermer, Joachim,Hübner, Gerhard,Schellenberger, Alfred,Schowen, Richard L.
, p. 8402 - 8409 (1991)
Isotope effects ([rate constant for light isotopic substrate]/[rate constant for heavy isotopic substrate]) for the action of the thiamin diphosphate dependent pyruvate decarboxylase of Saccharomyces carlsbergensis (EC 4.1.1.1) on pyruvate, pyruvate-1-13C, pyruvate-2-13C, and pyruvate-3-d3 have been determined for each of the steady-state kinetic parameters k/A (second-order in pyruvate), k/B (first-order in pyruvate), and k (zero-order in pyruvate). The 1-13C effects are 1.008 ± 0.010 (k/A), 1.013 ± 0.024 (k/B), and 1.024 ± 0.006 (k). The 2-13C effects are 1.013 ± 0.009 (k/A), 0.951 ± 0.020 (k/B), and 1.039 ± 0.004 (k). The 3-d3 effects are 0.883 ± 0.013 (k/A), 0.881 ± 0.026 (k/B), and 1.057 ± 0.005 (k). Effects with 2-oxobutanoate and 2-oxobutanoate-3-d2 are 0.951 ± 0.012 (k/A), 0.821 ± 0.096 (k/B), and 1.057 ± 0.005 (k). Pyruvate decarboxylase was already known to be hysteretically activated by the substrate, with pyruvate binding to the regulatory site with dissociation constant 8 mM and producing unimolecular activation (0.46 s-1) and deactivation (0.033 s-1). The isotope effects lead to rate constants for substrate binding to the catalytic site of 8.2 × 104 M-1 s-1, for substrate departure from the catalytic site of 120 s-1, for decarboxylation of 640 s-1, and for product release of 640 s-1. Pyruvate decarboxylase increases the rate of decarboxylation of pyruvate by thiamin alone by a factor of 3 × 1012 at pH 6.2, 30°C. Under these conditions, conversion of activated enzyme and pyruvate to the enzymic species preceding decarboxylation is 4 × 1012 times faster than the specific-base-catalyzed addition of thiamin to pyruvate. The enzymic species preceding decarboxylation reverts to activated enzyme and free pyruvate 6 × 109 times faster than the specific-base-catalyzed reversion of the adduct of thiamin and pyruvate to thiamin and free pyruvate. Enzymic decarboxylation is 107 times faster than decarboxylation of the adduct of thiamin and pyruvate.
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.
