820-10-0Relevant articles and documents
Peroxo-Cerium(IV)-Containing Polyoxometalates: [CeIV6(O2)9(GeW10O37)3]24-, a Recyclable Homogeneous Oxidation Catalyst
Qasim, Hafiz M.,Ayass, Wassim W.,Donfack, Patrice,Mougharbel, Ali S.,Bhattacharya, Saurav,Nisar, Talha,Balster, Torsten,Solé-Daura, Albert,R?mer, Isabella,Goura, Joydeb,Materny, Arnulf,Wagner, Veit,Poblet, Josep M.,Bassil, Bassem S.,Kortz, Ulrich
supporting information, p. 11300 - 11307 (2019/09/07)
The class of peroxo-cerium-containing polyoxometalates has been discovered via the synthesis of the 9-peroxo-6-cerium(IV)-containing 30-tungsto-3-germanate, [CeIV6(O2)9(GeW10O37)3]24- (1). Polyanion 1 consists of a cyclic [Ce6(O2)9]6+ assembly that is stabilized by three dilacunary [GeW10O37]10- Keggin fragments. The title polyanion 1 is solution-stable, on the basis of 183W nuclear magnetic resonance, and was shown to act as a recyclable homogeneous catalyst for the selective, microwave-activated sulfoxidation of the model substrate methionine to the sulfoxide in the absence and to the sulfone in the presence of hydrogen peroxide. Solution and solid-state Raman as well as solid-state infrared studies of 1 demonstrated the complete loss (and regain) of the nine peroxo groups in situ during the catalytic cycle, suggesting that the peroxo-free {Ce6(GeW10)3} skeleton remains most likely intact during the catalytic cycle. Solid-state X-ray photoelectron spectroscopy measurements showed that peroxo loss is accompanied by reduction of the cerium ions from +4 to +3, which is fully reversible. Density functional theory calculations are in complete agreement with all of these observations and furthermore suggest that the reduction of the six cerium(IV) ions is accompanied by the formation of molecular dioxygen.
Kinetics and mechanism of iridium(III) catalysed oxidation of DL-methionine by alkaline hexacyanoferrate(III)
Dharma Rao,Baby Nirmala,Vani
, p. 365 - 371 (2013/05/22)
Iridium(III) catalysed oxidation of DL-methionine by hexacyanoferrate(III) was studied spectrophotometrically in aqueous alkaline medium at 30 ± 0.1°C at a constant ionic strength. A micro amount of iridium(III) was sufficient to catalyse the slow reaction between DL-methionine and hexacyanoferrate(III). The reaction is first order in both hexacyanoferrate(III) and iridium(III) concentrations. The order with respect to DL-methionine is fractional. Increase in the alkali concentration increases the reaction rate. Methionine sulfone was found to be the main product of oxidation and it was identified by IR and mass spectra. Hexacyanoferrate(II), the other product was found to have no effect on reaction rate. The active species of oxidant and catalyst are [Fe(CN)6]3- and [IrCl3(H 2O)2OH]- respectively. A possible mechanism was proposed and the activation parameters were computed with respect to the slow step of the reaction.
Reactive ZrIV and HfIV butterfly peroxides on polyoxometalate surfaces: Bridging the gap between homogeneous and heterogeneous catalysis
Carraro, Mauro,Nsouli, Nadeen,Oelrich, Holger,Sartorel, Andrea,Soraru, Antonio,Mal, Sib Sankar,Scorrano, Gianfranco,Walder, Lorenz,Kortz, Ulrich,Bonchio, Marcella
supporting information; experimental part, p. 8371 - 8378 (2011/09/19)
At variance with previously known coordination compounds, the polyoxometalate (POM)-embedded ZrIV and HfIV peroxides with formula: [M2(O2)2(α-XW 11O39)2]12- (M=ZrIV, X=Si (1), Ge (2); M=HfIV, X=Si (3)) and [M6(O 2)6(OH)6(γ-SiW10O 36)3]18- (M=ZrIV (4) or Hf IV (5)) are capable of oxygen transfer to suitable acceptors including sulfides and sulfoxides in water. Combined 1HNMR and electrochemical studies allow monitoring of the reaction under both stoichiometric and catalytic conditions. The reactivity of peroxo-POMs 1-5 is compared on the basis of substrate conversion and kinetic. The results show that the reactivity of POMs 1-3 outperforms that of the trimeric derivatives 4 and 5 by two orders of magnitude. Reversible peroxidation of 1-3 occurs by H 2O2 addition to the spent catalysts, restoring oxidation rates and performance of the pristine system. The stability of 1-3 under catalytic regime has been confirmed by FT-IR, UV/Vis, and resonance Raman spectroscopy. The reaction scope has been extended to alcohols, leading to the corresponding carbonyl compounds with yields up to 99 % under microwave (MW) irradiation. DFT calculations revealed that polyanions 1-3 have high-energy peroxo HOMOs, and a remarkable electron density localized on the peroxo sites as indicated by the calculated map of the electrostatic potential (MEP). This evidence suggests that the overall description of the oxygen-transfer mechanism should include possible protonation equilibria in water, favored for peroxo-POMs 1-3. Copyright
Halogenated fatty acid amides and cyclic depsipeptides from an eastern Caribbean collection of the cyanobacterium Lyngbya majuscula
Jimenez, Jorge I.,Vansach, Tifanie,Yoshida, Wesley Y.,Sakamoto, Bryan,Poerzgen, Peter,Horgen, F. David
supporting information; experimental part, p. 1573 - 1578 (2010/03/31)
A lipophilic extract of an eastern Caribbean collection of Lyngbya majuscula yielded two new halogenated fatty acid amides, grenadamides B (1) and C (2), and two new depsipeptides, itralamides A (3) and B (4), along with the known compounds hectochlorin a
L-Methionine related 1-amino acids by acylase cleavage of their corresponding N-acetyl-DL-derivatives
Bommarius, Andreas S.,Drauz, Karlheinz,Guenther, Kurt,Knaup, Guenter,Schwarm, Michael
, p. 3197 - 3200 (2007/10/03)
Acylase I from Aspergillus oryzae is an even more useful enzyme than suggested so far. Besides standard amino acids such as L-Met, L-Val and L-Phe, a number of additional sulfur- and selenium-containing amino acids can be obtained at useful reaction rates and in very high enantiomeric purity by kinetic resolution of the respective N-acetyl-DL-amino acids.
Oxidation of Methionine by Sodium N-Bromobenzenesulphonamide in Aqueous Solution. A Kinetic and Mechanistic Study
Ananda, S.,Rangappa, K. S.,Mahadevappa, D. S.
, p. 581 - 585 (2007/10/02)
Kinetics of oxidation of DL-methionine (Mt) in the presence of HCl, HClO4, H2SO4 and NaOH by sodium N-bromobenzenesulphonamide (BAB) have been investigated at 40 deg (and 30 deg in alkaline medium).The rate law is identical in the three acids, .In alkaline medium, the rate law shows a first order dependence each on and ->.Effect of halide (Cl- or Br-) ion was studied.Addition of the reaction product, benzenesulphonamide retards the rate.Variation of ionic strength has no effect on the rate.The solvent isotope effect was studied using D2O.Activation parameters have also been determined.Methioninesulphone is identified as the reaction product.Mechanism proposed and the derived rate laws are in agreement with the observed kinetics.
Oxidation of Methionine by Sodium N-Chlorotoluene-p-sulphonamide in Aqueous Solution: a Kinetic Study
Mahadevappa, D.S.,Ananda, S.,Gowda, N.M. Made,Rangappa, Kanchugarakoppal S.
, p. 39 - 44 (2007/10/02)
Kinetics of oxidation of DL-methionine (Mt) in the presence of HCl, HClO4, H2SO4, and NaOH by sodium N-chlorotoluene-p-sulphonamide (CAT) have been investigated at 30 deg C (and 35 deg C in alkaline medium) and the results are compared with those obtained with HOCl as the oxidant, in acid medium.The reactions follow identical kinetics, being first order each in and +> and zero order in .In alkaline medium the rate shows first-order dependence each on and .An inverse fractional order is noted in ->.Studies of solvent isotope effects using D2O showed a retardation of rate both in acid and alkaline media.The derived rate laws are consistent with the observed kinetics.
Kinetics and Mechanism of Oxidation of Methionine by Sodium N-Bromotoluenesulphonamide in Aqueous Solution
Mahadevappa, D. S.,Mohan, K.
, p. 748 - 751 (2007/10/02)
Kinetics of oxidation of DL-methionine (Mt) in the presence of HClO4, HCl, H2SO4 and NaOH by bromamine-T (BAT) has been investigated at 45 deg C.Some rate law is obtained in all the acid media which depends on 1, 2 and 00.Halide ions catalyse the reaction.In alkaline medium, the rate law shows first order dependence each on 0 and and is independent of 0.Addition of the reaction product, p-toluenesulphonamide retards the reaction in the alkaline medium.Solvent isotope effect has been studied.Mechanisms proposed and the derived rate laws are in agreement with the observed results.
A BIOMIMETIC HETEROATOM OXIDATION
Ganem, Bruce,Biloski, Alan J.,Heggs, Richard P.
, p. 689 - 690 (2007/10/02)
The oxidation of amines and sulfides to N-oxides, sulfoxides and sulfones is smoothly accomplished using 2-hydroperoxyhaxafluoro-2-propanol (HPHI).
