Oxidations by vanadium V

The oxidation by vanadium(V) of iron(II), a reaction in which a metal-oxygen bond is broken, takes place according to the stoichiometric equation 

Oxidation potentials lead to a value of 7.9 x 10 for the equilibrium constant. Kinetic data for the reaction (from 0 to 55.6 °C) in acid perchlorate solutions (over the range 0.047-1.0 M) have been obtained spectrophotometrically by following the disappearance of V(V) (which absorbs strongly between 305 and 350 m/i) as a function of time. The second-order nature of the rate law 

The three terms of this expression indicate three competitive activation processes, respectively 

Step (2.3), and AS, are 1.52 kcal.mole and —37.3 cal.deg . mole , respectively. It is noteworthy that the following reduction reactions of the analogous M02 actinide ions show a similar first-order hydrogen-ion dependence (NpOi- +Fe + ) , (Np02- - -Np + ) , (Pu02++Pu02 ) and (U02 -l-In Table 1 the activation parameters of the V(V)-t-Fe(II) reaction are 

ACTIVATION PARAMETERS FOR REACTIONS HAVING +4 ACTIVATED COMPLEXES  

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Dzhabarov FZ, Gorbachev SV (1965) Kinetics of the citric acid oxidation by vanadium) V) compounds. Zh Fiz Khim 39 2198 201... 

Raminelli C, Barreto WJ, Takashima K (2000) Citric acid oxidation by vanadium(V) in sulfuric acid medium kinetic and mechanistic study. Intern J Kinet 32 566-572... 

Phenanthrene can be directly oxidized by vanadium(V) oxide to 9,10-phenanthraquinone. Based on the resonance forms of phenanthrene, explain why the central ring is oxidized rather than the other rings. 

Anthraquinone itself is traditionally available from the anthracene of coal tar by oxidation, often with chromic acid or nitric acid a more modern alternative method is that of air oxidation using vanadium(V) oxide as catalyst. Anthraquinone is also produced in the reaction of benzene with benzene-1,2-dicarboxylic anhydride (6.4 phthalic anhydride) using a Lewis acid catalyst, typically aluminium chloride. This Friedel-Crafts acylation gives o-benzoylbenzoic acid (6.5) which undergoes cyclodehydration when heated in concentrated sulphuric acid (Scheme 6.2). Phthalic anhydride is readily available from naphthalene or from 1,2-dimethylbenzene (o-xylene) by catalytic air oxidation. 

The nitric acid oxidation of cycloalkenes yields, among other products, a,(0-dicarboxylic acids.663,664 The reaction is catalyzed by vanadium(V) ion.665,666 Oxidations with H202,284,667 PhIO,650 or KHSO5650 catalyzed by heteropoly acids284,650 or tungstic acid667 have been recently described. 

K. K. Sen Gupta and S. N. Basu, Kinetics and mechanism of oxidation of some aldoses by vanadium(V) in perchloric acid medium, Carbohydr. Res., 72 (1979) 139-149. 

Scheme 24. The synthesis of tylophorine by vanadium(V)-mediated oxidative cyclization of septicine.

Oxidative coupling of a protected tyrosine substrate promoted by vanadium(V) reagents. 

Effecting deposition-precipitation by decreasing the pH level is interesting with metal ions present in the stable state in aqueous solution as anions [35]. With silica no interaction is observed, which has led to the development of the electrochemical reduction procedure. To apply metal ions, such as, molybdenum or vanadium, on alumina, a homogeneous decrease in pH level is interesting. The pH level has been decreased by injection of nitric acid or perchloric acid and electro-chemically. However, the rate of crystallization of the hydrated oxides of vanadium(V) and molybdenum(VI) was observed to be fairly low. To prevent dissolution of the alumina supports the pH cannot be decreased to levels below about 3, at which the crystallization of the hydrated metal oxides does not proceed rapidly. 

Chromium(VI) oxide nitrate and vanadium(V) oxide nitrate were first prepared by Schmeisser and Lutzow by the reaction of chromium(VI) oxide and vanadium(V) oxide with nitrogen(V) oxide. The nitrogen(V) oxide was prepared in the solid state by dehydration of fuming nitric acid with phosphorus(V) oxide. The method described below simplifies the preparation of anhydrous nitrogen(V) oxide and shortens significantly the time required. The products obtained can be protected from hydrolysis by totally excluding water from the all-glass system. 

Tungstophosphates probably constitute the largest number of different heteropolyanions, yet the synthesis of specific (transition metal)-substituted positional isomers of these species has been hampered because of doubt in the formulation of precursor lacunary (defect) polyanions and uncertainties in product identification. This work describes the preparation of several vanadium(V) substituted dodecatungstophosphates. Replacement of tungsten(VI) by vanadium(V) produces significantly stronger oxidants. 

Bonds to Oxygen.—Kinetic data on the oxidation of arsenic(ni) by vanadium(v)... 

R 353 K. P. Bryliakov and E. P, Talsi, Intermediates of Asymmetric Oxidation Processes Catalysed by Vanadium (V) Complexes , Kinet. Catal., 2003, 44, 334... 

M. Ziglio and K. Takashima [Int. J. Chem. Kinet., 27, 1055-1064 (1995)] studied the oxidation of malic acid by vanadium (V) in aqueous sulfuric acid ... 

The e.s.r. spectra of oxovanadium ions in redox systems have been reported. The interaction of free-radicals generated using the reactions of cerium(iv) or ferrous ions with hydrogen peroxide with oxovanadium(v), produces a complex which decays in a first-order manner (k = 6-2 s at 22 °C) with the formation of vanadium(iv). The oxidation of phenetidines by bromate is catalysed by vanadium(v) and kinetic parameters involved in the interactions of various substrates with vanadium(v) have been correlated with electron configurations. The redox behaviour of oxo-3,5-disulphocatecholatovanadium(v) has been studied and the acidity dependence in the reaction with phenylethyl alcohol reported. In the... 

Table 2 Thermodynamic parameters for oxidation of organic substrates by vanadium(v) from ref 9, Introduction and references therein)...

The kinetics of the oxidation of hexoses, pentoses, hexitols and pentitols by vanadium(V, cerium(IV), manganese(III) and thallium-(III) in aqueous acidic media have been claimed to proceed via a... 

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