The Kinetics of the Chromate-Dichromate Reaction as Studied by a Relaxation Method

Swinehart, James H.; Castellan, Gilbert W.

doi:10.1021/ic50012a033

Cited by 29 publications

(12 citation statements)

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“…The equilibrium (14), where any co-ordinated The close similarity of k, and k, to rate coiistants for other hydrogen-ion dependent substitution reactions of [HCrO,]-is consistent with an S N ~ process. We are not able to test whether the same mechanism applies to substitution reaction of molybdenum(v1) in acid solution, because, whereas (15) can be reformulated in the desired form (since the acid dissociation constant for [H,Mo0a2+ has been determined, Table 2), the acid dissociation constant for [HMoOa + is not known, and we are unable to evaluate the forward rate constant when ( 14) is expressed as in (18).…”

Section: Resultsmentioning

confidence: 99%

Kinetics of the rapid monomer–dimer equilibration of molybdenum(VI) in aqueous perchloric acid solutions

Ojo¹,

Taylor²,

Sykes³

1975

J. Chem. Soc., Dalton Trans.

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The monomer-dimer equilibration of molybdenurn(vi) in 0.2--3.0~ perchloric acid solutions, / = 3 O M (LiCIOJ, has been studied at 25 "C. Spectrophotometric measurements are consistent with the presence of a monomeric species, [HMoO,] +, and dimeric species, [HzMo20a]2+ and [H,Mo2O,'J3+, in agreement with previous work by Krumenacker. Evidence for the further monomeric species [ H2M00,12+ has been obtained. Kinetic studies using the temperature-jump technique indicate a major pathway (i) for equilibration, with rate constant k, = Chemistry, The University, Leeds LS2 9JT(1.71 f 0.10) x lo5 I mol-l s-l and k-, = (3.20 f 0.20) x lo3 s -l . The equilibration (ii). appears to con-tribute to a small extent with k, = (0.3 f 0.3) x los I mol-l s-l and k-2 = (30 f 20) s-l. (ii) ONE of the most interesting features of the chemistry even in >Lini-acid solutions), and examples with molybof molybdenum is the prevalence of dimeric species. denum-(11) and -(Iv) are now well established. .Those of molybdenum(v) are extensive (and present Monomeric and dimeric forms of molybdenum(Ir1) have 1 See for example, P. C . H. Mitchell, Co-ordination Chem. Rev., been identified,4 while molybdenum(v1) is known t o 1966, 1, 316.

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Section: Resultsmentioning

confidence: 99%

Kinetics of the rapid monomer–dimer equilibration of molybdenum(VI) in aqueous perchloric acid solutions

Ojo¹,

Taylor²,

Sykes³

1975

J. Chem. Soc., Dalton Trans.

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“…Schwarzenbach and Meier (4) interpreted the results of their study of pH change accompanying dilution of concentrated dichromate solutions in a constant-flow apparatus on the assumption that there was zero-order hydroxide dependence. Attempts by Lifshitz and Perlmutter-Hayman (5) to utilize the thermal change in the dichromate-hydroxide reac-T h e kinetics of the monomer-dimer equilibrium was further studied by a "concentration-jump" relaxation method by Swinehart and Castellan (6), and the results of this investigation were found to be consistent with the assumed rate-determining step:…”

Section: Introductionmentioning

confidence: 63%

Oxygen exchange between chromium(VI) oxyanions and water

Holyer¹,

Baldwin²

1967

Can. J. Chem.

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The rate of oxygen exchange between 0 ' 8 enriched CrOd2-, HCr04-, Cr2072-and solvent water has been measured as a function of pH and total chromium(V1) concentration. The exchange can be explained in terms of the dimerization equilibria HCrOa-+ C r 0 4 2 -e Cr2072-+ OH-and 2HCr04-Cr2Ol2-+ Hz0 except a t high pH, where slow pH-independent exchange is observed. Rate constants for the reactions of the dimerization equilibria have been evaluated from the exchange results, and are in agreement with values obtained by a variety of other methods.

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“…Measurements with 0.075 M BeCrO, at pH = 4.67 and 298 K lead to two relaxation times: A fast one was attributed to the substitution process with r = 17.2 ms and an apparent energy of activation of 60 f 13 kJ/moI. A slower process with a relaxation time of 4.1 s and an apparent energy of activation of 36 2 7 kJ/mol is presumably due to the formation of bichromate (see [25]). Measurements on 0.1 M beryllium benzosulfonate at pH = 2.86 failed to show a relaxation process.…”

Section: Beryllium Acetate In Water-dimethylsulfoxidementioning

confidence: 97%

On Complex Formation in Mixed Solvents

Strehlow¹,

Busse²

1984

Ber Bunsenges Phys Chem

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In a mixture of solvents S1 and S2 a cation Mz+ forms “solvatomers” of the type M(S1)i(S2)k‐iz+, where k is the coordination number of the cation and i = 0 to k. The rate of substitution of a solvating molecule by a ligand LzL depends in general on the specific solvatomer and on the solvent molecule being substituted. – Kinetic measurements are reported on systems with the cations Be2+, Al3+, and Ni2+, the ligands sulfate, rhodanide and acetate and the solvent pairs water‐dimethylsulfoxide, water‐N‐methylformamide, water‐hexamethylphosphoric triamide, water‐formamide and methanol‐dimethylsulfoxide. – Some rules concerning the kinetic behaviour of such systems have been developed. In particular, an explanation is presented for the different kinetics observed with tetrahedrally coordinated complexes (k = 4) and with octahedrally coordinated ones (k = 6).

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The Kinetics of the Chromate-Dichromate Reaction as Studied by a Relaxation Method

Cited by 29 publications

References 0 publications

Kinetics of the rapid monomer–dimer equilibration of molybdenum(VI) in aqueous perchloric acid solutions

Kinetics of the rapid monomer–dimer equilibration of molybdenum(VI) in aqueous perchloric acid solutions

Oxygen exchange between chromium(VI) oxyanions and water

On Complex Formation in Mixed Solvents

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