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1.
Summary The kinetics of OsO4-catalysed oxidation of cyclopentanol, cyclohexanol and cyclooctanol by alkaline hexacyanoferrate(III) have been studied at low [OH–] so that the equilibrium between alcohol and alkoxide ion is not unduly shifted towards the latter. The reaction shows a first-order dependence in [OH–]. The order of the reaction with respect to cycloalcohol is fractional, indicating the formation of an intermediate complex with OsVIII since the order with respect to hexacyanoferrate(III) ion is zero. The order with respect to OsVIII may be expressed by the equation kobs=a+b[OsVIII]. The analysis of the rate data indicates a significant degree of complex formation between [OsO3(OH)3]– and ROH. It was found that the bimolecular rate constant k for the redox reaction between complex and OH–k1, the forward rate constant for the formation of alkoxide ion. The activation parameters of these rate constants are reported. 相似文献
2.
Ramesh C. Kapoor Raj N. Mehrotra Shared K. Vajpai Purnima Chaudhary 《Transition Metal Chemistry》1991,16(1):65-70
Summary The kinetics of the OsVIII-catalysed oxidation of glycols by alkaline hexacyanoferrate(III) ion exhibits zerothorder dependence in [Fe(CN)
6
3–
] and first-order dependence in [OsO4]. The order with respect to glycols is less than unity, whereas the rate dependence on [OH–] is a combination of two rate constants; one independent of and the other first-order in [OH–]. These observations are commensurate with a mechanism in which two complexes, [OsO4(H2O)G]– and [OsO4(OH)G]2–, are formed either from [OsO4(H2O)(OH)]– or [OsO4(OH)2]2– and the glycol GH, or by [OsO4(H2O)2] and [OsO4(H2O)(OH)]– and the glycolate ion, G–, which is in equilibrium with the glycol GH through the reaction between GH and OH–. Hence there is an ambiguity about the true path for the formation of the two OsVIII-glycol complexes. A reversal in the reactivity order of glycols in the two rate-determining steps, despite the common attack of OH– ion on the two species of OsVIII-complexes, indicates that the two complexes are structurally different because S changes from the negative (corresponding to k11) to positive (related to k2). 相似文献
3.
Kondapi A. Kumar Pathaneni Sivaswaroop Kanuri Jaganmohana Rao Panuganti V. K. Rao 《Transition Metal Chemistry》1987,12(5):441-444
Summary The oxidation of MnII by S2O8
2– to MnVII in phosphoric acid medium proceeds via a stable MnIII and MnIV species. The reaction is catalysed by Ag+ and exhibits first order dependence on [S2O8
2–], [Ag+] and, is independent of [MnII]. The [H+] has no significant effect on the reaction. It is observed that the PO4
3– ion stabilises the transient manganese(III) and manganese(IV) species by forming a stable and soluble phosphato-complexes. The activation parameters for the two stages of oxidation, namely MnII MnIV and MnIVMnVII at 25° C are Ea=52 ±4 kJ mole–1, S*=–57±2 JK–1 mole–1 and Ea =56±4 kJ mole–1, S*=–44±2 JK–1 mole–1, respectively. A mechanism consistent with the experimental observations is proposed.Presented at the National Symposium on Reaction Kinetics and Mechanism, Department of Chemistry, University of Jodhpur, Jodhpur, India, Nov. 15–18, 1986. 相似文献
4.
Gianantonio Battistuzzi Marco Borsari Daniela Dallari Raffaele Battistuzzi 《Transition Metal Chemistry》1995,20(2):212-219
Summary
Tris-, bis- and mono-ligand complexes of NiII with 1-phenyl-4, 6-dimethylpyrimidine-2-thione (L) having the general formulae NiL3X2·2H2O (X = ClO
inf4
p–
, BF
inf4
p–
), NiL2X2 (X = Cl–, Br–, SCN– or NO
inf3
p–
), NiL2X2·EtOAc (X = Br– or I–), NiL2X2·H2O·EtOH (X = I– or NO
inf3
p–
) and NiLCl2·3H2O, were synthesized and their structures deduced from i.r. and electronic spectra, and magnetic properties. The combined evidence is consistent with an octahedral coordination for the NiII ion in all the complexes, with the ligand acting as a bidentate N,S-chelating agent. Spectral evidence, conductivity data and electro-chemical results in DMF solution show that the complexes undergo solvolysis readily. Polarographic and c.v. data for the [NiL3](ClO4)2·2H2O complex and for the [Ni-(DMF)6](ClO4)2-L systems, at increasing ligand concentrations, have shown that in DMF solution the [Ni(DMF)6]2+ cation prevails and that the thiopyrimidine-containing species, [NiL(DMF)5]2+ (L = N-monodentate ligand)
, can be formed only in the presence of a large excess of free ligand.Author to whom all correspondence should be directed. 相似文献
5.
Michail Bogdanov Ryszard Gryboś Alina Samotus Konstantin Bogolitsyn 《Transition Metal Chemistry》1993,18(6):599-603
Summary The kinetics of the reduction of octacyanometallates(IV) in alkaline aqueous medium have been studied spectrophotometrically. The experimental results are in agreement with following rate law:-d[M(CN)
inf8
sup3–
]/dt = k
obs[M(CN)
inf8
sup3–
]2[OH–][Na+] where k
obs = 4.1 × 10–2M–3s–1 (Mo) and 4.0 × 10–4 M–3 s–1 (W). The rate data were used to calculate the thermodynamic activation parameters H
and S
. A mechanism of the reaction is discussed.On leave from Faculty of Chemistry, Forest Engineering Institute, Archangelsk, Russia. 相似文献
6.
Pesyeti Saroja Mulakaluri Prasad Rao Sushama Kandlikar 《Transition Metal Chemistry》1990,15(5):351-356
Summary The oxidation ofi-propanol (IPA) by N-bromosuccinimide (NBS) in basic solution was investigated separately in the presence of RuIII, OsVIII and RuIII + OsVIII ions. The order in [IPA] was found to be 0.7, 0.5 and 0.3 respectively in the above three cases in the concentration range studied. The order in [NBS] was unity in the presence of RuIII chloride but was found to be zero in the case of OsVIII and RuIII+OsVIII catalysis. The order in [metalion] was found to be nearly unity in all the three catalysed reactions. Increase in [–OH] increased the rate of reaction while addition of succinimide retarded the rate of reaction. Decrease in dielectric constantsof the medium decreased the rate of oxidation. The pseudo first order rate constants (k), zero order rate constants (k0) and the formation constants (kf) of the substrate-catalyst complexes and the thermodynamic parameters have been evaluated. Suitable mechanisms in conformity with the experimental observations have been proposed for the three catalysed reactions. 相似文献
7.
Summary The reversible complex formation between 2-(2-aminoethyl) benzimidazole (AEB) and nickel(II) was studied by stopped flow spectrophotometry at I = 0.30 mol dm–3. Both the neutral and monoprotonated form of AEB reacted to give the NiAEB2+ chelate. At 25 °C, the rates and activation parameters for the reactions NiII + AEB
NiAEB2+ and NiII + AEBH+
NiAEB2+ + H+ are k
f
L(dm–3 mol–1 s–1) = (2.17 ± 0.24) × 103, H
(kJ mol–1) = 40.0 ± 0.8, S
(JK–1 mol–1) = – 47 ± 3 and k
inff
pHL
(dm3 mol–1 s–1) = 33 ± 10, H
(kJ mol–1) = 42.0 ±2.7, S
(JK–1 mol–1) = – 72 ± 9. The dissociation of NiAEB2+ was acid catalysed and k
obs for this process increased linearly with [H+] in the 0.01–0.15 mol dm–3 (10–30 °C) range with k
H(dm3 mol–1s–1) (25 °C) = 329 ± 6, H
(kJ mol–1) = 40 ± 2 and S
(JK–1 mol–1) = – 61 ± 8. The results also indicated that the formation of NiAEB2+ involves a chelation-controlled, rate-limiting process. Analysis of the S ° data for the acid ionisation of AEBH
inf2
p2+
and the formation of NiAEB2+ showed that the bulky AEBH+ ion has a solvent structure breaking effect as compared to AEB [s
aqS ° (AEBH+) – s
aq ° (AEB) = 69 JK–1 mol–1], while AEBH
inf2
p2+
is a solvent ordering ion relative to NiAEB2+ [s
aq° (NiAEB2+) – ovS
aq ° (AEBH
inf2
p2+
) = 11 JK–1 mol–1].Author to whom all correspondence should be directed. 相似文献
8.
A structural study of saturated aqueous solutions of some alkali halides by X-ray diffraction 总被引:2,自引:0,他引:2
The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H2O)–1], KCI [4.56 mol (kg H2O)–1], KF [16.15 mol (kg H2O)–1] and CsF [31.96 mol (kg H2O)–1] has been investigated by means of solution X-ray diffraction at 25°C. In the NaCI and KCI solutions about 30% and 60%, respectively, of the ions form ion pairs and the Na+–Cl– and K+–Cl– distances have been determined to be 282 and 315 pm, respectively. The average hydration numbers of Na+ and Cl– ions are 4.6 and 5.3, respectively, in the NaCI solution and those of K+ and Cl– ions in the KCI solution are both 5.8. In the KF solution, clusters containing some cations and anions, besides 1:1 (K+–F–) ion pairs, are formed. The K+–F– interatomic distance has been determined to be 269 pm, and nonbonding K+...K+ and F–...F– distances in the clusters are 388 and 432 pm, respectively, and the average coordination numbers n
KF
, n
KK
and n
FF
have been estimated to be 2.3, 1.9, and 1.6, respectively. In the highly supersaturated CsF solution an appreciable amount of clusters containing several caesium and fluoride ions are formed. The Cs+–F– distance in the cluster has been determined to be 312 pm, while the nonbonding Cs+...Cs+ and F–...F– distances are estimated to be 442 and 548 pm, respectively, the distances being about
and
times the Cs+–F– distance, respectively. The coordination numbers n
CsF
, n
CsCs
, and n
FF
in the first coordination sphere of each ion are 3.3, 2.3 and 5.3, respectively, and the result shows the formation of clusters of higher order than 1:1 and 2:2 ion pairs. These ion pairs and clusters may be regarded as embryos for the formation of nuclei of crystals and the results obtained in the present diffraction study support observations for the nucleation of the alkali halide crystals studied by molecular dynamics simulations previously examined. 相似文献
9.
Kinetics of oxidation of pyruvic acid by [ethylenebis(biguanide)]silver(III) in aqueous acidic media
The oxidation of pyruvic acid by the title silver(III) complex in aqueous acidic (pH, 1.1–4.5) media is described. The reaction products are MeCO2H and CO2, together with a colourless solution of the Ag+ ion. The free ligand, ethylenebis(biguanide) is released in near-quantitative yield upon completion of the reduction. The parent complex, [Ag(H2L)]3+ and one of its conjugate bases, [Ag(HL)]2+, participate in the reaction with both pyruvic acid (HPy) and the pyruvate anion (Py–) as the reactive reducing species. Ag+ was found to be catalytically inactive. At 25.0°C, I=1.0moldm–3, rate constants for the reactions [Ag(H2L)]3++HPy (k
1), [Ag(H2L)]3++Py– (k
2), [Ag(HL)]2++HPy (k
3) and [Ag(HL)]2++Py– (k
4) arek
1=(94±6)×10–5dm3mol–1s–1, (k
2
K
a+k
3
K
a1)= (1.3±0.1)×10–5s–1 and k
4=(58±4)×10–5dm3mol–1s–1, respectively, where K
a1is the first acid dissociation constant of the [Ag(H2L)]3+ and K
a is for pyruvic acid. A comparison between the k
1 and k
4 values is indicative of the judgement that k
2k
3. A one-electron inner-sphere redox mechanism seems more justified than an outer-sphere electron-transfer between the redox partners. 相似文献
10.
Summary The kinetics of aqueous polymerization of acrylonitrile monomer (M) initiated by the MnIII-KNCS redox system have been studied under deaerated conditions in the temperature range 26–40 °C at constant ionic strength. The overall rates of polymerization and the disappearance of MnIII were determined. The polymerization was initiated by the free radicals arising from the MnIII-thiocyanate redox reaction. The rate of polymerization was investigated at various concentrations of monomer and initiator. The effects of varying [MnIII], [NCS–], pH, total [P2O
inf7
sup4–
], added [MnII], metal ions, ClO
inf4
sup–
, Cl– and SO
inf4
sup2–
were examined. Dependence of the rate of polymerization on temperature was studied and activation parameters were computed from an Arrhenius plot. A suitable kinetic scheme consistent with the observed results is proposed and discussed. 相似文献
11.
By using pH-metric and conductometric methods it has been found that tetracycline (H3TC) forms with WO
4
2–
and MoO
4
2–
ions the following complex compounds: [WO3HTC]2–, [WO3(H2TC)2]2– and [MoO3(H2TC)2]2–. Stability constants log/gb
1
k
=7.86 and log
1
k
=7.80 for [WO3HTC]2– and [MoO3HTC]2–, respectively, have been calculated from pH-metric measurements. 相似文献
12.
Summary The kinetics and mechanisms of the oxidation of Nb(CN)
inf8
sup5–
by the oxyanions S2O
inf8
sup2–
, BrO
inf3
sup–
, and IO
inf4
sup–
have been investigated in alkaline aqueous media (pH 12). The second-order rate constant for the electron transfer reaction between Nb(CN)
inf8
sup5–
and S2O
inf8
sup2–
at 25.0 °C, I = 0.36m (K+), is 11.1± 0.3 m
–1
s
–1 with H
= 30 ± 2kJmol–1 and S
= - 125 + 7JK–1 mol–1. The rate constant for the oxidation of Nb(CN)
inf8
sup5–
by BrO
inf3
sup–
at 25.0 °C, I = 0.20m (Na+), is 2.39 ± 0.08m
–1
s
–1 with H = 28 ± 2kJmol–1 and S
= -139 ± 7JK–1mol–1. The oxidation of Nb(CN)
inf8
sup5–
by IO
inf4
sup–
proceeds by two parallel pathways involving the monomeric IO
inf4
sup–
ion and the hydrated dimer H2I2O
inf10
sup4–
. The second-order rate constant for the oxidation of Nb(CN)
inf8
sup5–
by monomeric IO
inf4
sup–
at 5.0 °C, I = 0.050m (Na+), is (3.3 ± 0.6) × 103
m
–1
s
–1 with H
= 75 ± 6 kJ mol–1 and S
= 94 ± 15 J K–1 mol–1, while the rate constant for the oxidation by H2I2O
inf10
sup4–
is (1.8 ± 0.1) × 103
m
–1
s
–1 with H
= 97 ± 5 kJ mol–1 and S
= 166 ± 16 J K–1 mol–1 under the same reaction conditions. The rate constants for each of the oxidants employed display specific cation catalysis with the order of increasing rate constants: Li+ < Na+ < NH
inf4
sup+
< K+ < Rb+ < Cs+, in the same direction as the electronic polarizability of the cations. The results are discussed in terms of the outer-sphere electron-transfer processes and compared with the corresponding data and mechanisms reported for other metal-cyano reductants. 相似文献
13.
Geoffrey J. Honan Stephen F. Lincoln Evan H. Williams 《Journal of solution chemistry》1978,7(6):443-451
The species UO2(DMSO)
5
2+
is shown from1H NMR studies to be the predominant dioxouranium(VI) species existing in dilute anhydrous acetonedimethyl sulfoxide (DMSO) solutions, and this result is compared with data reported for the analogous water-acetone-dimethyl sulfoxide system. Complete line-shape analyses of exchange-modified1H NMR line shapes indicate that the mechanism for DMSO exchange on UO2(DMSO)
5
2+
is probably of theD orI
D
type. A typical set of rate parameters arek
ex
(260°K) =273±14 sec–1, H
#=38.9±0.5 kJ-mole–1, and S
#=–47.5±1.8 J-oK–1-mole–1 for a solution in which [UO2(DMSO)5
2+], [DMSO], and [d
6 acetone] are, respectively, 0.01155, 0.0875, and 13.00 moles-dm–3. 相似文献
14.
Ashis Kumar Pondit Asim Kumar Das Soma Gangopadhyay Debabrata Banerjea 《Transition Metal Chemistry》1988,13(6):437-439
Summary Acid catalysed dissociation of the copper(II) and nickel(II) complexes (ML2+ of the quadridentate macrocyclic ligand 1, 5, 9, 13-tetraaza-2, 4, 4, 10, 12, 12-hexamethyl-cyclohexadecane-1, 9-diene (L) has been studied spectrophotometrically. Both complexes dissociate quite slowly with the observed pseudo-first order rate constants (kobs) showing acid dependence; for the nickel(II) complex (kobs)=kO+kH[H+], the ko path is however absent with the copper(II) complex. At 60°C (I=0.1M) the kH values areca 10–4 M–1 s–1 for both complexes; k
H
Cu
/k
H
Ni
=ca. 3.9, comparable to some other square-planar complexes of these metal ions. The rate difference is primarily due to H values [copper(II) complex, 29.4±0.5 kJ mol–1; nickel(II) complex, 35.6±1.5 kJ mol–1] with highly negative S values [for copper(II), –215.5 ±6.1 JK–1 mol–1 and for nickel(II), –208.1 ±5.6 JK–1 mol–1] which are much higher than the entropy of solvation of Ni2+ (ca. –160 JK–1 mol–1) and Cu2+ (ca. –99 JK–1 mol–1) ions; significant solvation of the released metal ions and the ligand is indicated. 相似文献
15.
Nadimpalli Sridevi Padmavathy Jelaja Yusuff Karukapadath K. M. 《Transition Metal Chemistry》2001,26(3):315-321
The nature of the diperiodatocuprate(III) (DPC) species present in aqueous alkaline medium has been investigated by a kinetic and mechanistic study on the oxidation of iodide by DPC. The reaction kinetics were studied over the 1.0 × 10–3–0.1 mol dm–3 alkali range. The reaction order with respect to DPC, as well as iodide, was found to be unity when [DPC] [I–]. In the 1.0 × 10–3–1.0 × 10–2 mol dm–3 alkali region, the rate decreased with increase in the alkali concentration and a plot of the pseudo-first order rate constant, k
versus 1/[OH–] was linear. Above 5.0 × 10–2 mol dm–3, a plot of k
versus [OH–] was also linear with a non-zero intercept. An increase in ionic strength of the reaction mixtures showed no effect on k at low alkali concentrations, whereas at high concentrations an increase in ionic strength leads to an increase in k. A plot of 1/k
versus [periodate] was linear with an intercept in both alkali ranges. Iodine was found to accelerate the reaction at the three different alkali concentrations employed. The observed results indicated the following equilibria for DPC.[Cu(H2IO6)2]3- [Cu(H2IO6)]- + H2IO6
3-
[Cu(H2IO6)] + OH- [Cu(HIO6)]- + H2OA suitable mechanism has been proposed on the basis of these equilibria to account for the kinetic results. 相似文献
16.
Summary The copper(III)-imine-oxime complexes [CuIII(Enio)]+ and [CuIII(Pre)]+ {EnioH2 =N,N-ethylene bis(isonitrosoacetylacetoneimine) and PreH2 = N,N-propylene bis (isonitrosoacetylacetoneimine)} react very rapidly with iodide. The rate law under fixed conditions for the reaction is given by the equation: –d[CuIII]/dt = (2k2[I–] + 2k3[I–]2)[CuIII] The [CuIII(Enio)]+ reaction was pH-independent whereas the [Cu (Pre)]+ reaction rate increased with increasing pH. Both the k2 and the k3 pathways are believed to involve one-electron transfer. An inner-sphere mechanism may operate in the pathway, first-order in [I–]. 相似文献
17.
Frank J. Millero Sara Sotolongo David J. Stade Carmen A. Vega 《Journal of solution chemistry》1991,20(11):1079-1092
The oxidation of Fe(II) with H2O2 has been measured in NaCl and NaClO4 solutions as a function of pH, temperature T (K) and ionic strength (M, mol-L–1). The rate constants, k (M–1-sec–1), d[Fe(II)]/DT=-k[Fe(II)][2O2]at pH=6.5 have been fitted to equations of the formlog k = log k0+ AI
1/2+BI+CI
1/2/T
Where log k0=15.53-3425/T in water; A=–2.3, –1.35; B=0.334, 0.180; and C=391, 235, respectively, for NaCl (=0.09) and NaClO4 ( =0.08). Measurements made in NaCl solutions with added anions yield rates in the order B(OH)
4
–
>HCO
3
–
>ClO
4
–
>Cl–>NO
3
–
>SO
4
2–
and are attributed to the relative strength of the interactions of Fe2+ or FeOH+ with these anions. The FeB(OH)
4
+
species is more reactive while the FeCO
3
0
, FeCl+, FeNO
3
+
and FeSO
4
0
species are less reactive than the FeOH+ ion pair. The general trend is similar to our earlier studies of the oxidation of Fe(II) with O2 except for B(OH)
4
–
. The effect of pH on the logk was found to be a quadratic function of the concentration of H+ or OH– from pH=4 to 8. These results have been attributed to the different rate constants for Fe2+ (k0) and FeOH+ (k1) which are related to the measured k by, k=k0Fe + k1FeOH, where i is the molar fraction of species i. The rates increase due to the greater reactivity of FeOH+ compared to Fe2+. k0 is independent of composition and ionic strength but k1 is a function of ionic strength and composition due to the interactions of FeOH+ with various anions. 相似文献
18.
Yu. B. Tsaplev 《High Energy Chemistry》2004,38(3):174-179
Alkaline hydrolysis of nitroglycerin (G) was studied using the chemiluminescent reaction of the hydrolysis products with 4-dimethylaminophthalhydrazide (L). The chemiluminescence kinetics follows the pseudo-unimolecular law, with the rate constant k
1 proportional to [OH–]. The apparent bimolecular constant k
2 = k
1/[OH–] is equal to 0.021 l mol–1 s–1. The chemiluminescence quantum yield per one nitroglycerin molecule G = (1.3 ± 0.3) × 10–3 photons per one molecule ([G0] [L]), and the reactant chemiluminescence quantum yield upon excitation by species X formed from G in the course of hydrolysis is (2.6 × 0.5) × 10–2 photons per molecule ([G] [L0]]). Hence, it follows that the hydrolysis of 100 nitroglycerin molecules results in about five X molecules exciting chemiluminescence. The effects of temperature, ionic strength, and composition of the solution on k
2 were studied. Quantum-chemical calculation on the interaction of – ion with G molecule shows a possibility for peroxynitrite formation upon approach of the ion to the nitro group within the NO2 plane. If the approach occurs not in the NO2 plane, the conventional hydrolysis mechanism with substitution at nitrogen is realized. 相似文献
19.
Summary Reaction of CrCl3(DMF)3 with [15]aneN4 (L; L = 1,4,8,12-tetra-azacyclopentadecane) gives the green trans-{Cr([15]-aneN 4)Cl2}Cl in high yield. The base hydrolysis kinetics of the cations [CrLCl2]+ and [CrLCl(OH)] + have been investigated over a temperature range. For the dichloro complex, k
OH = 1.03 dm3 mol–1 s–1] at 25° C with H
=30.4 kJmol–1 and S
inf298
sup
= -143 JK–1 mol–1. The substantial negative entropy of activation implies more association of water in the loss of Cl– from the conjugate base in a DCB mechanism. The kinetic parameters for the chlorohydroxo complex are k
OH = 1.9 × 10–2dm3mol–1 s–1 at 25°C with H
= 78.3kJmol–1 and H
inf298
sup
= -15 J K–1 mol –1. The chlorohydroxo complex probably has the trans
VI configuration with the chloride ligand on the same side of the equatorial plane as the four chiral sec-NH groups. The visible spectra of a variety of complexes trans-[Cr(L)XY]
n+ (X = Y = Cl, OH, OH2; X = Cl, Y = OH) have been determined. 相似文献
20.
Summary Cyanide ion reacts with [Fe(Par)2]2–,i.e. Par=4-(2-pyridylazo)resorcinol to form a 113 mixed cyanocomplex. The reaction has been studied spectrophotometrically at 720 nm
max, pH=11.5±0.02, and I=0.1 M (NaClO4) at 25±0.1°C. The order with respect to cyanide varies from one to two at high and low cyanide concentrations respectively. The rate constants for respective reactions are k1=(6.1±0.3)×10–2 M–1 s–1, k2=(12.6±1.0) M–2 s–1. The reverse reaction does not occur at a measurable rate even in presence of a large excess of Par. These observations suggest that [Fe(Par)2]2– forms a mixed [FePar(CN)3]3– complex in presence of an excess of cyanide ion. The activation parameters for the reaction have been calculated and used to support a three step mechanism consistent with these results. The effect of ionic strength tends further support to the mechanism. 相似文献