Effects of nonionic, cationic, and anionic micelles on the kinetics of the complexation reaction of nickel (II) with pyridine-2-azo-p-dimethylaniline

Carbone, Antonio I.; Cavasino, F. Paolo; Dio, Emanuele Di; Sbriziolo, Carmelo

doi:10.1002/kin.550180602

Cited by 17 publications

(4 citation statements)

References 28 publications

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“…The kinetic parameters of this reaction, as obtained through the Robinson version of the pseudophase model for micellar catalysis, are sensitive to variations in micelle structure and dynamics. The use of nonionic or cationic surfactants causes inhibition of the complexation . Reinsborough et al investigated the influence of the addition of cations on the catalytic effect produced by micelles, as well as the influence of the micellar structure and the effect exerted by zwitterionic surfactant solutions .…”

Section: Introductionmentioning

confidence: 99%

“…The use of nonionic or cationic surfactants causes inhibition of the complexation. 11 Reinsborough et al investigated the influence of the addition of cations on the catalytic effect produced by micelles, 12 as well as the influence of the micellar structure 13 and the effect exerted by zwitterionic surfactant solutions. 14 The studies on micellar systems were extended using fluorate surfactants 15 and mixtures of surfactants 16 and included the effect exerted by additives such as alcohols 17 and ureas on micellization.…”

Section: Introductionmentioning

confidence: 99%

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Metal−Ligand Complexation in Water-in-Oil Microemulsions. I. Thermodynamic Approach

Fernández¹,

García‐Río²,

Knörl³

et al. 2003

Langmuir

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The complexation constants of Ni 2+ and Co 2+ with pyridine-2-azo-p-dimethylaniline (PADA) were determined in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water microemulsions at 25 °C. The results show that the complexation constants depend on the microemulsion composition. In all cases, the values of the apparent complexation constants are greater than those obtained in bulk water. To carry out a quantitative interpretation of the experimental results, we propose a complexation scheme that considers the microheterogeneous character of the microemulsion. It was found that the PADA is distributed between the continuous medium and the interface of the latter, whereas the Ni 2+ or Co 2+ ions are distributed between the aqueous microdroplet and the interface. If we consider an ionic exchange equilibrium between the counterion (Na + ) of the AOT and the reactive cation (Ni 2+ or Co 2+ ), it is possible to obtain the true complexation constants at the interface of the microemulsion. The values obtained for the true complexation constants decrease as the water content of the microemulsion increases and are always lower than the values obtained in bulk water. The interaction of interfacial water with the surfactant headgroup in the microemulsion causes an increase in the electronic density on the oxygen atoms of water and a consequent increase in the interaction H 2O‚‚‚M 2+ , which in turn leads to a greater stabilization of the ion with respect to that in bulk water. As the water content decreases, this interaction becomes stronger but the quantity of water molecules available for hydration decreases. This situation results in destabilization of the ion and an increase in its complexation capacity.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metal−Ligand Complexation in Water-in-Oil Microemulsions. I. Thermodynamic Approach

Fernández¹,

García‐Río²,

Knörl³

et al. 2003

Langmuir

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“…16 #20 micelle and water using the relationship between the formation rate of their nickel(II) complexes and the concentration of the micelle. An inhibition effect of Triton X-100 micelle on the rate of formation of nickel(II) with pyridine-2-azo-p-dimethylaniline has been reported by Carbone et al, 18 and the phenomenon can be well explained only by the partitioning of the ligand between water and the pseudophase. In these studies, the deceleration effect found in the present study was not observed.…”

Section: Correction For the Rate Of Complex Formation With Htfa In Trmentioning

confidence: 80%

Unusually Slow Extraction Rate and Mechanism of Iron(III) with Trifluoroacetylacetone in Triton X-100 Micellar System. Part II. Interfacial Transport

Inaba

2000

ANAL. SCI.

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As has been demonstrated in Part I, 1 the rate of formation/extraction of iron(III) with a kind of trifluoromethylsubstituted β-diketone (HA), trifluoroacetylacetone (1,1,1-trifluoro-2,4-pentanedione; Htfa) in aqueous Triton X-100 micellar solution system is sometimes slower than that estimated from the complex formation rate in the single aqueous solution, although the formation reaction proceeds only in the bulk aqueous phase. The difference in the rates observed and estimated are found to be larger when the ligand anion concentration in the bulk aqueous phase is higher and/or the surfactant concentration is higher. In such conditions, the molar fraction of the extracted tris-complex (FeA3) to the whole complex species in the system (FeA 2+ , FeA2 + , FeA3 and FeA3m) becomes higher. The formation reaction in the present micellar system is essentially controlled only by the formation of the mono-complex in the bulk aqueous phase and the equilibria among the three complex species in the bulk aqueous phase (FeA 2+ , FeA2 + and FeA3) are established while the reaction proceeds; hence, the deceleration phenomenon is assumed to be due to a slow material transport of the extractable tris-complex from the bulk aqueous phase to the micellar pseudophase.In the present part of the series, the rate of material transport of the tris-complex from the bulk aqueous phase to the micellar pseudophase has been directly measured using a novel micellarconcentration-jump stopped-flow technique in order to learn the reason for the slow extraction of iron(III) with Htfa into Triton X-100 micellar pseudophase. ExperimentalAll the reagents, instruments and experimental conditions are similar to those used in Part I. 1 The measurements for the material transport of the tris-complex were carried out as follows. An acidic metal solution containing 2 × 10 -4 M iron(III), 4 × 10 -3 -2 × 10 -2 M Htfa and 0.2, 0.5 or 1.0% Triton X-100, and an acidic ligand solution containing 4 × 10 -3 -3 × 10 -2 M Htfa and 0.8 -9.8% of the surfactant were mixed up and the change of absorbance at 435 nm was monitored by the stoppedflow spectrophotometer. The ligand anion concentration in the bulk aqueous phase of the resulting solution was controlled similar to that in the starting metal solution to avoid changes of total concentrations of complex species in the resulting solution just after the mixing with formation/decomposition due to some changes of the ligand anion concentration. The rate constants were taken as the average of results for a minimum of 5 kinetic runs. The absorbance and the pH of the resulting solutions were also monitored after the extraction equilibria were established. Data TreatmentIn the present paper, the chemical species in the micellar pseudophase are denoted by subscript "m", those in the bulk aqueous phase by lack of subscript, and those on the basis of total volume of the micellar solution by subscript "t". The subscript "(S)" denotes the species in the starting metal solution and "(R)" denotes a species in the resulting soluti...

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“…Therefore in the present case the reaction shown in scheme 1 applies. Such a scheme has been proposed by Carbone et al to explain the complex formation 14 between Ni(II) and pyridine-2-azo p-dimethyl aniline. The apparent rate constant is m k given by 2 Since the rate decreases from a maximum as the anionic surfactant concentration increases, k w can be neglected with respect to the other term in the numerator of (2) and the rearrangement of this expression yields Examination of the binding constants reveals that K s values are much larger than K o values.…”

Section: Experimental -Materials and Methodsmentioning

confidence: 96%

Kinetic investigation of the oxidation of N-alkyl anilines by peroxomonophosphoric acid in anionic surfactant sodium lauryl sulphate

Panigrahp

Panda

2000

J Chem Sci

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Kinetics of oxidation of N-methyl and N-ethyl aniline by peroxomonophosphoric acid (PMPA) in aqueous and 5% (v/v) acetonitrile medium respectively have been studied in presence of anionic micelles of sodium lauryl sulphate (SLS) at different pH. Oxidation rate of both the substrates increases up to a certain [SLS] much below the critical micellar concentration (cmc) after which the rate is retarded. Kinetic data have been used to compute the binding constants of both substrate and oxidant with the micelle. A scheme explaining the kinetic data has been proposed.

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Effects of nonionic, cationic, and anionic micelles on the kinetics of the complexation reaction of nickel (II) with pyridine-2-azo-p-dimethylaniline

Cited by 17 publications

References 28 publications

Metal−Ligand Complexation in Water-in-Oil Microemulsions. I. Thermodynamic Approach

Metal−Ligand Complexation in Water-in-Oil Microemulsions. I. Thermodynamic Approach

Unusually Slow Extraction Rate and Mechanism of Iron(III) with Trifluoroacetylacetone in Triton X-100 Micellar System. Part II. Interfacial Transport

Kinetic investigation of the oxidation of N-alkyl anilines by peroxomonophosphoric acid in anionic surfactant sodium lauryl sulphate

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