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1.
The kinetics of the oxidation of glycol by dihydroxyditelluratoargentate (Ⅲ) complex(DDA) was studied in alkaline medium with spectrophotometry(in a temperature range of 16.6-40 ℃).The first-order rates with respect to glycol and Ag(Ⅲ) were all found.The rates increased with the increase in [OH-] and decreased with the increase in [TeO2-4].No effect was found with the addition of KNO3 and no free radical was detected.In view of this,the dihydroxymonotelluratoargentate(Ⅲ) species(DMA) is assumed to be the active species.A plausible mechanism involving a two-electron transfer is proposed,and the rate equation derived from the mechanism can explain all experimental observations.Activation parameters of the rate-determining step and constants are evaluated. 相似文献
2.
Gupta Kalyan K. Sen Bhattacharjee Nandini Pal Biswajit Ghosh Saktiprosad 《Transition Metal Chemistry》1999,24(3):268-273
The kinetics of oxidation of the neutralized -hydroxy acids: lactic, -hydroxyisobutyric, mandelic, benzilic and atrolactic acids by tris(pyridine-2-carboxylato)manganese(III) have been studied. The reactions were carried out in a Na(pic)-picH [Na(pic) = sodium salt of pyridine-2-carboxylic acid and picH = pyridine-2-carboxylic acid] buffer medium in the 4.89–6.10pH range. The oxidation rate was found to be independent of pH, and rate follows the order: benzilate > mandelate >atrolactate>lactate > -hydroxy isobutyrate. The oxidation products are MeCHO, Me2CO, PhCHO, Ph2CO and PhCOMe for the respective reactions. A mechanism is proposed involving intermediate formation of hepta-coordinated MnIII complexes in a fast step. The complexes then decompose to give free radicals and MnII in the rate determining step. The free radicals subsequently react with another molecule of the MnIII species to give the respective carbonyl compounds in a fast step. 相似文献
3.
The authors present the results of a kinetic investigation concerning the formation and growth of the primary particles of
the ferrite phase in isothermal conditions, in static and well-stirred regimes. The kinetics of coprecipitation is described
with the help of equations corresponding to the homogeneous nucleation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
IntroductionZincisanessentialtraceelementtoorganism .α Aminoacidisthebasicunitofproteinrelatedwithlife .L α Leu(leucine)isoneofeightsortsofaminoacidsindispensabletolifewhichareabsorbedfromfoodbecauseitcannotbesyn thesizedinhumanbody .Thecomplexesofzincsaltswithα aminoacidasadditivehaveawideapplicationinmedicine ,foodstuffandcosmetics.1 3Thesyntheticmethodsofthecom plexesofzincsaltswithα aminoacidhavebeenreviewed .4 ,5ThesolubilityofZnSO4 Leu H2 Osystemat 2 98 15Khasbeeninvestigatedbys… 相似文献
5.
Janusz Chatłas 《Transition Metal Chemistry》2005,30(1):58-62
The kinetics of anation of hexaaquachromium(III) by thiocyanates follows the rate law: –d[complex]/dt=k[NCS] (20–40°C, [NCS–]=0.1–0.6M, I=2.0M, pH=1.0). The specific salt effect has been studied for five media: NaCl, NaBr, NaClO4, KCl and CsCl. The series of chloride (Na+, K+ and Cs+) salts show a negligible effect on the anation rate. On the contrary, the series of sodium salts (Cl–, Br– and ClO
4
–
) reveal a marked difference in the reaction rate. The anation rate decreases sharply with the ionic strength increase (I=0.2–2.0M, NaCl). The results were interpreted within the frame of fast equilibria of ion-pair formation followed by an interchange mechanism step. The difference of reaction rate is a result of competition between anions (thiocyanates and supporting electrolyte anions) to the complex cation at an ion-pair formation process. 相似文献
6.
The thermal dehydration reaction of potassium titanium oxalate, K2TiO(C2O4)2·2H2O, has been studied by means of thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) in nitrogen atmosphere at different heating rates. K2TiO(C2O4)2·2H2O dehydrates in a single step through a practically irreversible process. The activation energy involved and its dependence on the conversion degree were estimated by evaluating the thermogravimetric data according to model-free methods, and values of activation energy were determined for the dehydration reaction. Activation energy values were also evaluated from DSC data using isoconversional methods. The complexity of the dehydration of K2TiO(C2O4)2·2H2O is illustrated by the dependence of E on the extent of conversion, ?? (0.05??????????0.95). 相似文献
7.
A new method of synthesis 2,2-dimethylolpropionic acid from 2,2-dimethylolpropionaldehyde was put forward. The electrochemical
oxidation behavior of 2,2-dimethylolpropionaldehyde has been investigated on a Ti/SnO2 + Sb2O4/PbO2 electrode by cyclic voltammetry (CV) and stable polarization curves in sulfuric acid. The results showed that it was an irreversible
reaction controlled by diffusion. The formation mechanism of 2,2-dimethylolpropionic acid in the sulfuric acid was then proposed
and the transfer coefficients of the reaction were calculated. It was concluded that RCHO+ỌHads→RCHOỌHads was the rate-determining step in the electrolysis process. The rate of this step obtained from the assumed process agrees
well with experiment. 相似文献
8.
Fe(III) chloride hydrate (FeCl3·xH2O) undergoes simultaneous dehydration and dehydrochlorination from its molten phase in the temperature range 100–200C. The kinetics of these two parallel thermal processes has been studied by both isothermal and non-isothermal methods. Whereas for the dehydration reaction at temperature below 125C a second order rate model (F2) fits well, a three-dimensional diffusion (D3) model is found to fit better at temperature above 135C. For the dehydrochlorination reaction an interface growth controlled model of 1/3 order (F 1/3) appears to be the most suitable over a wide range of reaction. Dynamic thermogravimetry reveals two major steps in the temperature range 50–250C. The first step which corresponds to the loss of about 4 mols of H2O, invariably follows second order kinetics (F2). The second step which is predominantly a process of dehydrochlorination, generally fits mixed diffusion controlled models due to the overlapping with the dehydration process. There is an excellent agreement in results among the isothermal and non-isothermal methods of determining kinetic parameters.The authors are thankful to the Director, R. R. L. Bhubaneswar for his kind permission to publish this paper. One of the authors (SKM) is grateful to the Council of Scientific and Industrial Research, New Delhi, for the award of a Research Fellowship. 相似文献
9.
10.
FewcompoundswithMninthe 5oxidationstatewerestructuraIlycharacterizedsofaLC.L.HilIlfirstdeterminedthecrystalstructUreoftheMn(V)complex:NMnTpMPP-Nitriodotrtrakis(p-methoxyphenyl)porphinnato-manganese(V).Thepapers'-'reportedseveralnovelmanganese(V)and(Vl)complexes.RecentpublicationshavebeenestablishedthatthecoordinationcompoundsofhighvaIentmanganesedisplaymanyinterestingfeatures.Theyshowabilitytoundergointramolecularinterligandormetal-ligandelectrontransferreaction,especiallyonthenatUreo… 相似文献
11.
Introduction In the field of thermal analysis kinetics, there have been many kinetic models and methods of processing the corresponding data, which can depict the most probable kinetic mechanism of solid state reactions, such as the method combining differential and integral methods,1-6 the method combining isothermal and non-isothermal processes7,8 and method of TA curve shape,9,10 and so on. Recently, based on the predeces-sor抯 work, a more complete kinetic method of process-ing thermal ana… 相似文献
12.
The product and kinetics studies of 2,3,6-trimethylphenol (TMP) oxidation by 30% aqueous 22 in the presence of a heterogeneous catalyst, TiO2–SiO2 aerogel, are performed in an MeCN medium. The main reaction products are 2,3,5-trimethyl-1,4-benzoquinone and 2,2",3,3",6,6"-hexamethyl-4,4"-biphenol. The reaction is first-order in 22 and fractional order (1–0) in TMP. The reaction rate is proportional to the catalyst amount and depends on the water concentration in the reaction mixture in a complex manner. The results suggest the formation of an active intermediate on the titanium center. In this intermediate containing both a TMP molecule and the hydroperoxide group, inner-sphere one-electron oxidation of TMP occurs to give the phenoxyl radical. 相似文献
13.
The kinetics of H2S destruction in the radiolysis of CH4–H2S and CH4–H2S–O2 mixtures has been studied. It has been shown that G(–H2S) depends on amounts of hydrogen sulfide and the presence of oxygen in the starting mixture and is within the range of 5–13 mol/100 eV. G(H2) decreases with the increases of O2 content and amounts to the constant value of 2. 相似文献
14.
Kinetics and Mechanism of Oxidation of Glycol by Dihydroxydiperiodatonickelate ( Ⅳ )Complex in Aqueous Alkaline Medium 总被引:1,自引:0,他引:1
The kinetics of oxidation of glycol by dihydroxydiperiodato nickelate ( Ⅳ) complex (DDN) was studied by spectrophotometry in aqueous alkaline medium in a temperature range of 25-40℃. The reaction was found to be first order with respect to Ni( Ⅳ ) and also to be first order with respect to glycol. The rate increases with the increase in [OH ] and decreases with the increase in [IO-4], showing that dihydroxymonoperiodatonickelate ( Ⅳ )(DMN) is the reactive species of oxidant. Salt effect indicated that the reaction is of ion-dipole type. No free radical was detected. A mechanism of an inner-sphere two-electron transfer reaction involving a preequilibrium between DDN and DMN is proposed, and the rate equation derived from the mechanism can explain all experimental observations. Activation parameters of the rate-determing step and the equilibrium constants were calculated. 相似文献
15.
Rita Das Nigamananda Das Anadi C. Dash Ansuman Roy Shyamal K. Sarkar 《Transition Metal Chemistry》1996,21(1):90-94
Summary The reaction of ()-(tetren)CoOH2+ with S2O
3
2-
in the 7.25–8.28 pH range at 20–40 °C yielded S- (yellow) and O- (purple) bonded thiosulfato(tetren)cobalt(III) complexes, the former in larger quantities. The rate determining step is preceded by diffusion-controlled ion-pair [(tetren)CoOH2+,S2O
3
2-
] formation. Replacement of coordinated OH- by S2O
3
2-
is interpreted in terms of an internal conjugate base mechanism: (tetren)CoOH2+ (tetren-H)CoOH
2
2+
, the reactive amido conjugate base being generated by intramolecular proton transfer from the coordinated NH site.In acid medium the S-bonded (tetren)Co(S2O3)+ is highly stable to redox decomposition, in contrast to its pentaammine analogue. The complex however, undergoes base hydrolysis yielding the corresponding hydroxo complex. The rate and activation parameters for the base hydrolysis have been reported. Photolysis of O- and S-bonded isomers of [(tetren)CoS2O3]+ in acidic medium at 254 and 313 nm, respectively, yielded aquation products accompanied by some decomposition of S2O
3
2-
. 相似文献
16.
Gordana A. Milovanović Ferenc T. Pastor Goran M. Petković Marija Todorović 《Mikrochimica acta》2004,144(1-3):51-56
The kinetics of the iodide-catalyzed Mn(III) metaphosphate–As(III) reaction was studied in the presence of orthophosphoric acid. The reaction rate was followed spectrophotometrically at 516nm. It was established that orthophosphoric acid increased the reaction rate and that the extent of the non-catalytic reaction was extremely small. A kinetic equation was postulated and the apparent rate constant calculated. The dependence of the reaction rate on temperature was investigated and the energy of activation and other kinetic parameters determined. Iodide was determined under the optimal experimental conditions in the range 0.6–2.5ng·mL–1 with a relative standard deviation of up to 6.7% and a detection limit of 0.12ngmL–1. The effect of foreign ions on the accuracy of the determinations was also investigated. 相似文献
17.
《Journal of Coordination Chemistry》2012,65(6):977-987
The tris(2-chloromethyl-4-oxo-4H-pyran-5-olato-κ2O5,O4)iron(III), [Fe(kaCl)3], has been synthesized and characterized by the crystal structure analysis, magnetic susceptibility measurements, Mössbauer, and EPR spectroscopic methods. The X-ray single crystal analysis of [Fe(kaCl)3] revealed a mer isomer. The magnetic susceptibility measurements indicated the paramagnetic character in the temperature range of 2 K–298 K. The EPR and Mössbauer spectroscopy confirmed the presence of an iron center in a high-spin state. Additionally, the temperature-independent Mössbauer magnetic hyperfine interactions were observed down to 77 K. These interactions may result from spin–spin relaxation due to the interionic Fe3+ distances of 7.386 Å. 相似文献
18.
Summary The kinetics of the oxidation of ascorbic acid by diaquatetrakis (2,2-bipyridine)--oxo diruthenium(III) in aqueous HClO4 were investigated. The dependence of the second order rate constantk
2 on [H+] is given by k
2=a+b[H+]–, indicating that both the undissociated form and the monoanion of ascorbic acid are reactive. Marcus theory was used to estimate the redox potential for the RuIII-O-RuIII/RuIII-O-RuII couple and a feasible mechanism has been proposed to explain the results. 相似文献
19.
20.
The kinetics of oxidation of pyruvate by diperiodatoargentate( III) ion (DPA) has been studied spec-trophotometrically in alkaline medium. It was found that the reaction order with respect to both DPA and pyruvate is unity and the rate equation can be expressed asThe rate increases with the increase in [OH ] and decreases with the increase in [periodate]. There is a positive ionic strength effect in this reaction system. A mechanism has been proposed to explain the experimental results. The observed activation parameters are presented. 相似文献