Studies on a Furane Analogue of Malachite Green. Protolytic Equilibria and Reaction Rate Constants of Furane Green in Aqueous Solutions.

Cigén, Rune; Bengtsson, Gösta; Theander, Olof; Hatanaka, Akikazu; Munch‐Petersen, Jon

doi:10.3891/acta.chem.scand.17-2091

Cited by 3 publications

(2 citation statements)

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“…Probably, this discrepancy is due to the possibility of H + ions concentrating in the Stern layer of anionic surfactant micelles due to electrostatic attraction at low micelles concentrations. This also accelerates the interaction of the dye with water, because the rate constant of this reac-tion increases with decreasing pH [16,17]. The H + ions concentrating in micelles decreases with increasing SDS concentration, which reduces this effect on the observed rate constant.…”

Section: The Results Of Quantitative Analysis According To Berezin's Model and Their Discussionmentioning

confidence: 98%

Quantitative analysis of micellar effect on the reaction rate of cationic triphenylmethine dyes with water according to Berezin’s model

2020

Chemical Series

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Several approaches quantitatively describe the effect of surfactant micellar solution on the reaction rate. The most used among them are Piszkiewicz’s, Berezin’s, and Pseudophase Ion-Exchange (PIE) models. The last-named was developed by Bunton and Romsted. Piszkiewicz’s model is based on representations of the micellization according to the mass action law with the formation of a catalytic micelle, which consists of some surfactant molecules and a substrate. In our previously paper, this model was used to explain the kinetic micellar effect on the reaction of cationic triphenylmethine dyes with water once again showed the main disadvantages of this approach. Berezin’s model is based on another model of micelle formation viz. the pseudophase model, and the binding of reagents by micelles is considered as the distribution of a substance between two phases. In this work, we aim to consider the applicability of Berezin’s approach for the interaction of malachite green and brilliant green cations with water molecule as a nucleophile in aqueous systems of nonionic, anionic, cationic, and zwitterionic surfactants. On the whole, Berezin's model performed well when applied to the description of the micellar effect on the reaction of similar dye with the hydroxide ion. However, it was revealed that this model does not take into account the change in the local concentration of the HO– ions due to a compression of the double electric layer upon addition of reacting ions to the system, as well as the constant of association of the HO– ions with cationic head groups of surfactant. In this case, when water is used as a nucleophile, the question of the degree of nucleophile binding can be solved differently. The PIE model is also based on a pseudophase model of micellization, but a substrate binding by micelles is considered as an association in a stoichiometric ratio of 1:1, and a nucleophile concentration is expressed in a local concentration based on the neutralization degree of micelles. Given the latter, its approach cannot be applied to the kinetic micellar influence on the reaction of cationic triphenylmethine dyes with water.

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Section: The Results Of Quantitative Analysis According To Berezin's Model and Their Discussionmentioning

confidence: 98%

Quantitative analysis of micellar effect on the reaction rate of cationic triphenylmethine dyes with water according to Berezin’s model

2020

Chemical Series

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“…This mechanism resembles the reactions of malachite green and related dyes in aqueous acidic media, which was considered in a vast set of papers by Ginzburg et al . , Cigen , and their followers . In this case, the triarylmethyl cation is liable to nucleophilic attack only at high pH values.…”

Section: Resultsmentioning

confidence: 99%

3,3′‐Dinitrophenolsulphonephthalein: an acid–base indicator dye with unusual properties

Mchedlov‐Petrossyan

Laguta

Shekhovtsov

et al. 2016

Coloration Technology

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This paper is devoted to the phenolsulphonephthalein nitro derivative 3,3 0 -dinitrophenolsulphonephthalein, also called nitrophenol violet (NPV). The neutral molecular form, H 2 R, was isolated as a sultonic tautomer, and an X-ray crystal structure analysis was carried out. UV-vis absorption spectra in methanol, DMSO, acetonitrile, and water at different pH values were ascribed to the molecular and anionic (H 2 R, HR À , and R 2À ) species. Whereas the pK a values of this acid-base indicator (HR À ¡ R 2À + H + ) in water and DMSO are close to those of 3,3 0 ,5,5 0 -tetrabromophenolsulphonephthalein (or bromophenol blue), replacing the four Br atoms with two NO 2 groups results in a pronounced tendency to carbinol formation. In weakly acidic aqueous media, the HR À anion slowly converts into the colourless carbinol H 2 ROH À . The latter is transformed to the orange carbocation only in concentrated (70-94 wt%) sulphuric acid. The formation of H 2 ROH À is atypical for the common sulphonephthalein indicators and should be ascribed to the enhanced positive charge density on the nodal carbon atom. The reaction mechanism and kinetic equation explaining this pH-dependent process are proposed, in addition to a kinetic study of the common process R 2À + HO À ? ROH 3À in the alkaline region. The numerical characterisation of the protolytic processes obtained for NPV is also helpful in gaining a better understanding of the properties of previously studied 3,3 0 ,5,5 0 -tetranitrophenolsulphonephthalein, which is much less accessible for a quantitative description.

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Kinetic Studies on the Decolorization Reaction of Rosaniline in Aqueous Acidic Medium

Sinha¹,

Katiyar²

1977

Bulletin of the Chemical Society of Japan

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The reaction responsible for the decolorization of rosaniline in acid medium has been studied spectrophotometrically. The rate-determining step has been found to be the reaction of the protonated dye cation with water molecule. Kinetic data have been analyzed on the basis of rate equations which were derived considering the complete protolytic scheme involving all the steps of the reaction of rosaniline in acid and alkaline media. The rate constant k1 for the ion-molecule reaction has been found to be independent of the dye concentration and hydrogen ion concentration. The apparent rate constant k at various hydrogen ion concentrations has been utilized for calculating the equilibrium constant for the fast protonation step. Effect of ionic strength in the range 0–0.27 indicates no substantial effect on the rate constant k1. Anomalous solvent effects were obtained suggesting the solvated nature of the reactants. The average energy of activation for the reaction of rosaniline in aqueous medium corresponded to 10.52 kcal. Chemical and kinetic evidence has been presented to prove the participation of water molecule in the rate-determining step.

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Studies on a Furane Analogue of Malachite Green. Protolytic Equilibria and Reaction Rate Constants of Furane Green in Aqueous Solutions.

Cited by 3 publications

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Quantitative analysis of micellar effect on the reaction rate of cationic triphenylmethine dyes with water according to Berezin’s model

Quantitative analysis of micellar effect on the reaction rate of cationic triphenylmethine dyes with water according to Berezin’s model

3,3′‐Dinitrophenolsulphonephthalein: an acid–base indicator dye with unusual properties

Kinetic Studies on the Decolorization Reaction of Rosaniline in Aqueous Acidic Medium

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