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Shweta J. Malode Jyothi C. Abbar Sharanappa T. Nandibewoor 《Monatshefte für Chemie / Chemical Monthly》2011,34(6):469-479
Abstract
The kinetics of the oxidation of ruthenium(III)-catalyzed oxidation of pentoxifylline (PTX) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.30 mol dm−3 was studied spectrophotometrically. The reaction between PTX and DPC in alkaline medium in the presence of Ru(III) exhibits 1:2 stoichiometry (PTX:DPC). The reaction was of first order in DPC, less than the unit order in [PTX] and [OH−] and negative fractional order in [IO4 −]. The order in [Ru(III)] was unity. Intervention of free radicals was observed in the reaction. The main products were identified by TLC and spectral studies including LC-MS. The oxidation reaction in alkaline medium has been shown to proceed via a Ru(III)-PTX complex, which reacts with monoperiodatocuprate(III) to decompose in a rate determining step followed by a fast step to give the products. The reaction constants involved in different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic quantities were also determined. The active species of catalyst and oxidant have been identified. 相似文献2.
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The oxidation kinetics of the 2-aminomethylpyridineCrIII complex with periodate in aqueous solution were studied and found to obey the rate law:Rate = [CrIII]T [IO4
-]{k1K2 + k2 K1 K3/[H+]}/{1+K1/[H+] + k2[IO4
-]+K1K3/[H+][IO4
-]} where K
1, K
2 and K
3 are the deprotonation of [Cr(L)2(H2O)]3+ and pre-equilibrium formation constants for [(L)2—Cr—OIO3]2+ and [(L)2—Cr—OH—OIO3]+ precursor complexes respectively. An inner-sphere mechanism was proposed. The effect of Cu2+ on the oxidation rate was studied over the (1.0–9.0) × 10−5 mol dm−3 range. The reaction rate was found to be inversely proportional to the Cu2+ concentration over the range studied.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Ahmed A. Abdel-Khalek Said M. Sayyah Fadia F. Abdel-Hameed 《Transition Metal Chemistry》1994,19(1):108-110
A novel chromium(III) complex of tetraoxalylurea was prepared. In aqueous solutions, [CrIII(H2L)(H2O)]+ (H2L = diprotonated tetraoxalylurea) is oxidized by IO
4
–
according to the rate law
相似文献
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Abdel-Khalek Ahmed A. Sayyah El-Said M. Ewais Hassan A. 《Transition Metal Chemistry》1997,22(6):557-560
Oxidation of the chromium(III)-l-arginine complex [CrIII(L)2(H2O)2]+ by periodate has been investigated. In aqueous solutions,
[CrIII(L)2(H2O)2]+ is oxidized by IO−4 according to the rate law: d[CrVI]/dt=k2K5[CrIII]T [IVII]T/1 +([H+]/K1)+K5[IVII]T where
k2 is the rate constant for the electron transfer process, K1 the equilibrium constant for the dissociation of [CrIII(L)2-
(H2O)2]+ to [CrIII(L)2(H2O)(OH)]+H+, and K5 the pre-equilibrium formation constant. Values of k2= 4.02×10−3s−1, K1=5.60×10−4m
and K5=171m−1 were obtained at 30°C and I=0.2m. Thermodynamic activation parameters were calculated. It is proposed that electron
transfer proceeds through an inner-sphere mechanism via coordination of IO−4 to chromium(III).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Pacholska E Espinosa E Guilard R 《Dalton transactions (Cambridge, England : 2003)》2004,(20):3181-3183
A meso-aryl-substituted face-to-face biscorrole was synthesised in a two-step reaction and the corresponding homo- and heterobimetallic complexes were obtained and fully characterised. 相似文献
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The kinetics and mechanism of the oxidation of [CrIII(DPA)(IDA)(H2O)]? (DPA = dipicolinate and IDA = iminodiacetate) by periodate in the presence of Mn(II) as a catalyst have been investigated. The rate of the reaction increases with increasing pH, due to the deprotonation equilibria of the complex. Addition of Mn(II) in the concentration range of (2.5–10) × 10?6 mol dm?3 enhanced the reaction rate; the reaction is first order with respect to both [IO4 ?] and the Cr complex, and obeys the following rate law: \( {\text{Rate}} = [ {\text{Cr}}^{\text{III}} ({\text{DPA}})({\text{IDA}})({\text{H}}_{2} {\text{O}})^{ - } ][{\text{Mn}}^{\text{III}} ]\{ (k_{7} + K_{1} k_{8} /[{\text{H}}^{ + } ]) + [{\text{I}}^{\text{VII}} ]((k_{9} k_{11} /k_{ - 9} + k_{11} ) + (K_{1} k_{10} k_{12} )/(k_{ - 10} + k_{12} )[{\text{H}}^{ + } ])\} . \) Catalysis by Mn(II) is believed to be due to initial oxidation of Mn(II) to Mn(III), which acts as the oxidizing agent. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4 ? to Cr(III). Thermodynamic activation parameters were calculated using the transition state theory equation. 相似文献
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