Search results for "Perchloric acid"
showing 9 items of 19 documents
Biomimetic oxygen reduction by cofacial porphyrins at a liquid-liquid interface.
2012
Oxygen reduction catalyzed by cofacial metalloporphyrins at the 1,2-dichlorobenzene−water interface was studied with two lipophilic electron donors of similar driving force, 1,1'-dimethylferrocene (DMFc) and tetrathiafulvalene (TTF). The reaction produces mainly water and some hydrogen peroxide, but the mediator has a significant effect on the selectivity, as DMFc and the porphyrins themselves catalyze the decomposition and the further reduction of hydrogen peroxide. Density functional theory calculations indicate that the biscobaltporphyr- in, 4,5-bis(5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl))-9,9-dimethylxanthene, Co2(DPX), actually catalyzes oxygen reduction to hydrogen p…
Indirect Catalytic Spectrophotometric Determination of Metamizol Following Oxidation by Lead Dioxide Immobilized in A Polyester Resin Bed
1996
Abstract A spectrophotometric-indirect procedure for the determination of metamizol is described. The method is based on the reaction of the drug in a solid-phase (lead dioxide immobilized in a polyester resin bed) in acidic media (perchloric acid 0.01 M as carrier). The lead dioxide reactor provides simultaneously an effective oxidation of the drug and a controlled liberation of Pb(II) which acts as catalyst on the reaction pyrogallol red-potassium persulphate; the oxidation of the red pyrogallol results in a less coloured solution. The decreased red colour (negative FIA peaks) is monitored at 520 nm. The calibration graph is linear in the interval 2–16 ppm in metamizol. The relative stand…
Clarification of the oxidation state of cobalt corroles inheterogeneous and homogeneous catalytic reduction of dioxygen
2008
Co(III) corroles were investigated as efficient catalysts for the reduction of dioxygen in the presence of perchloric acid in both heterogeneous and homogeneous systems. The investigated compounds are (5,10,15-tris(pentafluorophenyl)corrole)cobalt (TPFCor)Co, (10-pentafluorophenyl-5,15-dimesitylcorrole)cobalt (F 5PhMes 2Cor)Co, and (5,10,15-trismesitylcorrole)cobalt (Mes 3Cor)Co, all of which contain bulky substituents at the three meso positions of the corrole macrocycle. Cyclic voltammetry and rotating ring-disk electrode voltammetry were used to examine the catalytic activity of the compounds when adsorbed on the surface of a graphite electrode in the presence of 1.0 M perchloric acid, a…
Mechanism of four-electron reduction of dioxygen to water by ferrocene derivatives in the presence of perchloric acid in benzonitrile, catalyzed by c…
2004
The selective two-electron reduction of dioxygen occurs in the case of a monocobalt porphyrin [Co(OEP)], whereas the selective four-electron reduction of dioxygen occurs in the case of a cofacial dicobalt porphyrin [Co(2)(DPX)]. The other cofacial dicobalt porphyrins [Co(2)(DPA), Co(2)(DPB), and Co(2)(DPD)] also catalyze the two-electron reduction of dioxygen, but the four-electron reduction is not as efficient as in the case of Co(2)(DPX). The micro-superoxo species of cofacial dicobalt porphyrins were produced by the reactions of cofacial dicobalt(II) porphyrins with dioxygen in the presence of a bulky base and the subsequent one-electron oxidation of the resulting micro-peroxo species by…
Fine tuning of the catalytic effect of a metal-free porphyrin on the homogeneous oxygen reduction.
2011
The catalytic effect of tetraphenylporphyrin on the oxygen reduction with ferrocene in 1,2-dichloroethane can be finely tuned by varying the molar ratio of the acid to the catalyst present in the solution. The mechanism involves binding of molecular oxygen to the protonated free porphyrin base, in competition with ion pairing between the protonated base and the acid anion present.
Heterocyclic rearrangements. Synthesis of 1,2,4-oxadiazolo[2,3-a]pyrimidinium systems and their ring opening into pyrimidineN-oxides
1986
Reaction des methyl- et phenyl-5 amino-3 oxadiazoles-1,2,4 avec l'acetylacetone ou la benzoylacetone en presence d'acide perchlorique: obtention de methyl- et phenyl-2 methyl- et phenyl-5 methyl-7 oxadiazolo [2,3-a] pyrimidiniums-4 qui se decyclisent ensuite en oxydes-1 d'acylamino-2- et amino-2 methyl-4 methyl- et phenyl-6 pyrimidines
UV-Photometrische Analyse kationisch erzeugter Polystyrole, 2. Quantitative Bestimmung von Endgruppen in Polystyrolen, dargestellt mit Acylperchlorat…
1984
Acyl perchlorates generated in styrene without a solvent by acyl chlorides and silver perchlorate gave polystyrenes with covalently bonded acyl groups. In order to gain secured values their number average relative molecular masses (Mn) were determined by different methods. The polystyrenes could be hydrogenated with hydrogen and Raney nickel at room temperature and under atmospheric pressure without attacking the phenolic nuclei. In addition IR data and a UV absorption at 294 nm of the polystyrenes revealed the presence of and olefinic bond, which was also found in a polystyrene obtained by polymerisation with perchloric acid. Also the quantitative evaluation of the hydrogeneation by UV abs…
[21] Assay of blood glutathione oxidation during physical exercise
1995
Publisher Summary This chapter describes a method to accurately measure glutathione (GSH) and glutathione disulfide (GSSG) in the blood of humans and animals that perform physical exercise. With this method, it is possible to assess the oxidative stress associated with physical exercise by measuring changes in the blood GSH/GSSG ratio. Glutathione measurement is performed by a modification of the glutathione S -transferase method of Brigelius et al. This is based on the conjugation of chlorodinitrobenzene with GSH catalyzed by glutathione S -transferase. The adduct formed, S-(2,4-dinitrophenyl)glutathione, exhibits a maximum of absorbance at 340 nm. The precipitation of proteins is carried …
One-pot synthesis of fluorinated 2-amino-pyrimidine-N-oxides. Competing pathways in the four-atom side-chain rearrangements of 1,2,4-oxadiazoles
2006
Abstract Trifluoromethylated 2-amino-pyrimidine N-oxides have been synthesized by reaction of the 3-amino-5-methyl-1,2,4-oxadiazole with trifluoromethyl-β-diketones in the presence of perchloric acid, followed by hydrolysis. In this ring-to-ring transformation an initial formation of (unisolated) 1,2,4-oxadiazole-pyrimidinium salts, and subsequent ring-opening at the oxadiazole moiety occurs. Isolation of 2-(hydroxyamino)-pyrimidine from the reaction mixture evidenced the presence of a competing pathway where the N(4) nitrogen of the oxadiazole is involved in the formation of a regioisomeric pyrimidinium salt. The effect of the trifluoromethyl group on the product distribution is discussed.…