Kinetic-Fluorimetric Determination of Choline and Acetylcholine by Oxidation with Ce(IV)

Abstract

A kinetic fluorimetric method for the determination of choline and acetylcholine based on the oxidation of these analytes by Ce(IV) in a sulfuric acid medium yielding fluorescent Ce(III) is proposed. The calibration graph of each analyte is linear over the range 1.7x10^?5 ? 1×10^?3 M and the relative standard deviation is about 2% in both cases. The rate of appearance of Ce(III) fluorescence was found to be influenced by various processes in addition to the oxidation reaction and experiments were carried out in order to elucidate them.     

Oxidation of ethanol by Ce(IV) in acid nitrate medium

The oxidation kinetics of ethanol by Ce(IV) has been studied as a function of pH, nitrate and water concentration. Even at high concentration of H⁺ and NO ₃ ^– several species appear to exist. The oxidation is fastest in strongly acidic medium without added nitrate ions.

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Ce(IV) pH, . H⁺ NO ₃ ^– , Ce(IV). .

     

Kinetics of Oxidation of Diphenylmethane and Derivatives with Ce(IV) in Aqueous Acidic Acetonitrile

In aqueous acidic acetonitrilc solution cerium(IV) oxidizes diphenylmethane (Ph₂CH₂) to produce diphenylmethanol (Ph₂CHOH) first and then benzophenone (Ph₂CO). With the organic reductant in great excess, both the Ce(IV)-Ph₂CH₂ and Ce(IV)-Ph₂CHOH rcactions follow second-order kinetics. The rates of both reactions increase nonlinearly with increasing [H⁺] or with decreasing [H₂O]. Both kinetic and spectrophotometrc results indicate that replacement of water molecules by complex formation through the phenyl or hydroxyl group plays an important role in activating the reaction. Under similar conditions, the order of relative reactivities toward Ce(IV) oxidation is PhCH₂OH > CH₃CH₂OH > Ph2CHOH > Ph₂CH₂ > PhCH₃> (Ph₂CO, C₆H₆). Mechanistic interpretations of the kinetic results are presented.     

Oxidative Rearrangement via Oxycerication with Ce(IV) Salt

α-Arylpropanoic acids are pharmaceutically interesting compounds, some of them exhibit anti-flammatory and analgestic activities1. Even the enormous progress made in the synthesis of α-arylpropanoic acids by 1,2-aryl rearrangement of arylpropanone using thalium (III) nitrate1,2, silver (I) compounds,3,4 lead (IV) acetate5,6 and iodinate7 during the last decades. The route is, however, unsuitable for the preparation of pharmaceutical products (Naproxen, Ibuprofen and so on) because of the …     

Chemiluminescence system of Ce(IV)-RhB-bismerthiazol

A novel chemiluminescence system for the determination of bismerthiazol is first described in this paper. It is based on the chemiluminescence reaction of bismerthiazol and Ce(IV) in nitric acid solution. The emission intensity could be enhanced greatly by Rhodamine B. The chemiluminescence intensity was proportional to bismerthiazol concentration over the range 30–1000 μg/L. The detection limit was 12 μg/L (3σ) and the relative standard deviation is 2.4% for 500 μg/L of bismerthiazol (n = 11). The proposed method was successfully applied to the determination of bismerthiazol in water and in rice. The recovery was 96.4%–104.1%. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24(5): 593–595     

H2O2 Oxidation by Ce(IV) Contained Weakley-Type Heteropolyoxometalate for Various Alcohols

Catalytic activity of Ce(IV) contained Weakley-type heteropoly-oxometalate for the H₂O₂ oxidation of primary and secondary alcohols was evaluated for the first time. It was found that this catalyst exhibited a mild and thus quite selective activity, especially for benzylalcohols.     

Kinetics and Mechanism of Oxidation of Adipic Acid by Ce(IV) Ion in Acidic Medium

Kinetic study of oxidation of adipic acid by Ce(IV) ion in aqueous solution of sulphuric acid shows that the reaction follows first order kinetics in both Ce(IV) and adipic acid and the over all reaction order ascertained is two. The specific rate constant increases with an increase in the concentration of adipic acid. Effects of hydrogen ion concentration, bisulphate ion and temperature have been studied in detail. Various kinetic parameters have been computed. The experimental findings are consistent with the mechanism involving rapid resersible formation of an activated complex between Ce(IV) and adipic acid followed by a rate determining step involving C-C bond fission.     

Stereoselective addition of diorganyl chalcogenides to cyclohexene catalyzed with tin(IV) chloride

The addition of diorganyl disulfides and dimethyl diselenide to cyclohexene in the presence of tin(IV) chloride proceeded stereoselectively affording trans-adducts of 1:1 composition. No reaction occurs in the absence of tin(IV) chloride.     

Oxidation of p-chlorotoluene and cyclohexene catalysed by polymer-anchored oxovanadium(IV) and copper(II) complexes of amino acid derived tridentate ligands

3-Formylsalicylic acid (Hfsal), covalently bound to chloromethylated polystyrene (PS) and cross-linked with 5% divinylbenzene reacts with d,l-alanine and l-isoleucine to give the Schiff-base tridentate ligands PS-H(2)fsal-d,l-Ala and PS-H(2)fsal-l-Ile, respectively. These anchored ligands upon reaction with VOSO(4) and Cu(CH(3)COO)(2).H(2)O form the complexes PS-[VO(fsal-d,l-Ala)(H(2)O)], PS-[Cu(fsal-d,l-Ala)(H(2)O)], PS-[VO(fsal-l-Ile)(H(2)O)] and PS-[Cu(fsal-l-Ile)(H(2)O)]. The structures of these immobilized complexes have been established on the basis of scanning electron micrographs, spectroscopic (infrared, electronic and EPR), thermogravimetric and elemental analysis studies. The oxidation of p-chlorotoluene and cyclohexene has been investigated using these complexes as the catalysts in the presence of H(2)O(2) as the oxidant. Reaction conditions have been optimised by considering the concentration of the oxidant, the amount of catalyst used and the temperature of the reaction mixture. Under the optimised conditions, p-chlorotoluene gave a maximum of 14% conversion using PS-[VO(fsal-d,l-Ala)(H(2)O)] as the catalyst, with the main products having a selectivity order of: p-chlorobenzaldehyde > p-chlorobenzylalcohol > p-chlorobenzoic acid > 2-methyl-5-chlorophenol > 3-methyl-6-chlorophenol. The oxidation of cyclohexene with PS-[VO(fsal-d,l-Ala)(H(2)O)] proceeds with 79% conversion, which is followed by PS-[VO(fsal-l-Ile)(H(2)O)] with 77% conversion, and the oxidation of cyclohexene by Cu-based catalysts occurs with considerably lower conversions (29-32%). The selectivity of the products follows the order: 2-cyclohexene-1-ol > cyclohexene oxide > cyclohexane-1,2-diol > 2-cyclohexene-1-one. Recycling studies indicate that these catalysts can be reused at least three times without any significant loss in their catalytic potential. However, EPR studies indicate that while the polymer supported V(iv)O-complexes do not change after being used, the EPR spectra of the Cu-complexes show significant changes. The corresponding non-polymer bound complexes [VO(fsal-d,l-Ala)(H(2)O)], [Cu(fsal-d,l-Ala)(H(2)O)], [VO(fsal-l-Ile)(H(2)O)] and [Cu(fsal-l-Ile)(H(2)O)] have also been prepared in order to compare their spectral properties and catalytic activities. The non-polymer bound complexes exhibit lower conversion, along with lower turn-over frequency as compared to their polymer-bound analogues. Several EPR, (51)V NMR and UV-vis studies have been undertaken to detect the intermediate species, and outlines for the mechanisms of the catalytic reactions are proposed.     

Effect of Mn(II) and Ce(IV) Ions on the Oxidation of Lactic Acid by Chromic Acid

The kinetics and mechanism of lactic acid oxidation in the presence of Mn(II) and Ce(IV) ions by chromic acid were studied spectrophotometrically. The oxidation of lactic acid by Cr(VI) was found to proceed in two measurable steps, both of which gave pyruvic acid as the primary product in the absence of Mn(II). 2Cr(VI)+2CH₃CHOHCOOH → 2CH₃COCOOH+Cr(V)+Cr(III) Cr(V)+CH₃CHOHCOOH → Cr(III)+CH₃COCOOHThe observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II) and Ce(IV) on the lactic acid oxidation by Cr(VI). The reactivity of lactic acid depends upon the experimental conditions. It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II). It was examined that Cr(III) products resulting from the direct reduction of Cr(VI) by three-equivalent reducing agents. The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid]. The activation parameters E_a, ΔH^#, and ΔS^# were calculated and discussed.     

Adduct formation in Ce(IV) thenolytrifluoroacetonate

Russian Chemical Bulletin -     

Investigation of the interaction of Ce(IV) with diethylenetriaminepentaacetic acid

Conclusions The formation of a neutral monocomplex of Ce(IV) with diethylenetriaminepentaacetic acid was found by a spectrophotometric method. The instability constant of the complex at =1.0 and pH 1.4, the value of which was equal to (0.8±0.2)·10^–34, was calculated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2186–2189, October, 1970.     

Ce(IV)-induced polymerization of allyl methacrylate with cotton cellulose

Ce(IV)-induced polymerization of allyl methacrylate (AMA) with cotton cellulose was investigated under a variety of conditions. Polymer add-on was directly related to AMA concentration. The same holds good for Ce(IV) ion concentration up to a certain concentration (30 mmol/L), after which it decreases. Polymer add-on was higher at 60 than at 50 and 70°C. A methanol/water mixture (20/80) offers the best medium for polymerization. Addition of nitric acid (up to 400 mol equivalent/L) or perchloric acid (up to 800 mol equivalent/L) to the polymerization system caused significant enhancement in polymer add-on. The reverse was the case with sulphuric acid irrespective of the concentration used. A comparison between polymer add-on values based on increase in weight and those based on estimated allyl double bonds indicated that the latter undergo partial homopolymerization.     

Isolation of dithiocarbazate salts as oxinato-complexes of titanium(IV), zirconium(IV) and hafnium(IV)

Summary Ionic chelate complexes of the type, [(⁵-R)₂ML][dtz] [R=cyclopentadienyl (Cp) or indenyl (C₉H₇); M=Ti^IV, Zr^IV or Hf^IV; HL=oxine; dtz=phenyldithiocarbazate (PhNHNHCS₂)] have been synthesised and characterised. Conductance measurements indicate that the complexes are 11 electrolytes. From i.r. and u.v. spectral studies we conclude that the oxinato-group is chelating. Consequently there is tetrahedral coordination around the metal ion.¹H and¹³C N.m.r. studies are consistent with the stoichiometries. X-ray powder diffraction studies have been made for [(⁵-Cp)₂ZrL][dtz]. For [(⁵-Cp)₂TiL][dtz] and [(⁵-Cp)₂ZrL][dtz] thermal (t.g. and d.t.a.) and mass spectral studies have been carried out.     

Oxidation of Thiols to Their Disulfides with Bis Trinitratocerium (IV)l Chromate [Ce(NO3)312 CrO4 and Pyridinum Chlorochromate

Oxidation of thiophenols, benzyl thiol, and alkyl thiols with bis [trinitratocerium (IV)] chromate and pyridinum chlorochromate are investigated. Pyridinum chlorochromate is quite ineffective for the oxidative dimerization of alkyl thiols.     

Chemiluminescence of Ce(IV) and surfactant Tween 20

It was found that cerium(IV) reacted with surfactant Tween 20 in acidic medium to generate green chemiluminescence. The maximum emission wavelength was about 478 nm. The enhancement and inhibition of the CL reaction by some polyphenols and anilines was studied and the possibility of analytical application was explored.     

A Raman investigation of some metal (II) hexafluorosilicate (IV) and hexafluorotitanate (IV) salts

Raman data on M(II)(H₂O)₆SiF₆ (MNi, Fe, Mg, Zn) and M(II)(H₂O)₆TiF₆ (MNi, Zn) are presented. The results allow a positive identification of the symmetric MO stretch for the first time in these salts; other band assignments are also discussed. Low temperature (300⩽TK⩽15) results are also presented and a discussion of the mechanism of the phase transition at 120 K in NiTiF₆·6H₂O is given. It is shown that the phase transition in this salt has a different origin from that in the hexafluorosilicate salts.