Effect of medium on dissociation of carboxylic acids

Mollin, J.; Pavelek, Zdeněk; Navrátilová, Jitka; Recmanová, Alena

doi:10.1135/cccc19852670

Cited by 10 publications

(6 citation statements)

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“…If necessary, the dyes were also taken into account in the proton balance. Based on comparative analysis 1 of data, available from the literature, 15b, [16][17][18]22 the pK HA values of HCl and salicylic and benzoic acids were equated to 3.2, 8.2 and 12.3, and the logK f HA 2 À values to 2.2, 1.7 and 2.4, respectively. In the case of 5,5-diethylbarbituric acid, homoconjugation was not taken into account, because in another aprotic solvent, acetonitrile, the K f HA 2 À value for this acid is 50-100-fold lower than those for salicylic and benzoic acids.…”

Section: Dissociation Constants and Visible Spectra Of Dyes In Dmfmentioning

confidence: 99%

“…However, in DMF, and also in other aprotic media, the poorly solvated COO À group can strongly influence the charge distribution within structure 9 (see above). Both the ÁpK a values and the K a;0 =K a;1 and K a;1 =K a;2 ratios in various solvents are caused by the nature of dissociating groups, as well as by the tautomerization constants [Eqns (18)- (22)]. The medium effect for the pK a;0 value of rhodamine B is expressed by…”

Section: Tautomerism Of Molecules and Ions Of Xanthenes And Comparisomentioning

confidence: 99%

“…Analogously, taking into account the conventional character of graphical formulae, rhodamine B, N,N-diethylrhodol, halogen derivatives of fluorescein and of phenol red, in addition to sulfonefluorescein (22)(23)(24) can be depicted.…”

Section: Peculiarities Of Electroreduction Of Xanthene and Sulfonephtmentioning

confidence: 99%

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Dissociation, tautomerism and electroreduction of xanthene and sulfonephthalein dyes inN,N‐dimethylformamide and other solvents

Mchedlov‐Petrossyan

Kukhtik

Bezugliy

2003

J of Physical Organic Chem

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Protolytic equilibria in DMF of 10 dyes, fluorescein and its halogen derivatives, rhodamine B and N,Ndiethylrhodol, and of four sulfonephthaleins were studied by visible spectroscopy. The ratios of the stepwise dissociation constants of the substances in DMF, and the changes of these constants on transferring from water to DMF and other solvents, were explained taking into account the nature of functional groups and of the state of tautomeric equilibria. From the correlations between the Gibbs energies of tautomerization of the neutral species (quinonoid Ð colorless lactone) and the normalized Reichardt's parameter, E N T , the 'limiting' values of tautomerization constants of fluorescein and eosin at E N T ! 0 (non-polar aprotic media) were evaluated. The conversion of the neutral form of sulfonephthaleins into colorless sultones in DMF is demonstrated. The peculiarities of the reduction of the substances on a dropping mercury electrode in non-aqueous media were revealed, namely the differentiating action of DMF in the first and second stages of electroreduction of the R 2À anions.

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Section: Dissociation Constants and Visible Spectra Of Dyes In Dmfmentioning

confidence: 99%

Section: Tautomerism Of Molecules and Ions Of Xanthenes And Comparisomentioning

confidence: 99%

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Dissociation, tautomerism and electroreduction of xanthene and sulfonephthalein dyes inN,N‐dimethylformamide and other solvents

Mchedlov‐Petrossyan

Kukhtik

Bezugliy

2003

J of Physical Organic Chem

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“…To demonstrate the generalizability of our method A to other carboxylic acids, mixture HMs are constructed and calibrated for formic, acetic, and citric acid for known p K a . 67–69 Furthermore, we apply method B to formic and acetic acid to validate its applicability to other carboxylic acids. In the herein presented case studies, the assumption of a dilute ideal mixture does not hold strictly speaking, because acid concentrations surpass 0.1 mol L −1 , ionic strength exceeds 0.01 mol L −1 , and polyvalent ions occur.…”

Section: Resultsmentioning

confidence: 99%

Inline Raman Spectroscopy and Indirect Hard Modeling for Concentration Monitoring of Dissociated Acid Species

et al. 2020

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We propose an approach for monitoring the concentration of dissociated carboxylic acid species in dilute aqueous solution. The dissociated acid species are quantified employing inline Raman spectroscopy in combination with Indirect Hard Modeling (IHM) and Multivariate Curve Resolution (MCR). We introduce two different titration-based Hard Model (HM) calibration procedures for a single mono- or polyprotic acid in water with well-known (method A) or unknown (method B) acid dissociation constants pKa. In both methods, spectra of only one acid species in water are prepared for each acid species. These spectra are used for the construction of HMs. For method A, the HMs are calibrated with calculated ideal dissociation equilibria. For method B, we estimate pKa values by fitting ideal acid dissociation equilibria to acid peak areas that are obtained from a spectral HM. The HM in turn is constructed on the basis of MCR data. Thus, method B on the basis of IHM is independent of a priori known pKa values, but instead provides them as part of the calibration procedure. As a detailed example, we analyze itaconic acid in aqueous solution. For all acid species and water, we obtain low HM errors of less than 2.87Ã10-4 mol mol-1 in the cases of both method A and B. With only four calibration samples, IHM yields more accurate results than partial least squares regression. Furthermore, we apply our approach to formic, acetic, and citric acid in water, thereby verifying its generalizability as a process analytical technology for quantitative monitoring of processes containing carboxylic acids.

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“…The differences in pK* values of carboxylic acids in a solvent S and in water pK*(HA)s -pK*(HA)H20 = ilpK*(HA) are related to each other through 8 ilpK*(HA) = W. (ilpK(HAc))i ,…”

mentioning

confidence: 99%

Ratio of lyate ions activities in two-components protogenic solvents

Mollin

Pavelek

Kašpárek

1987

Collect. Czech. Chem. Commun.

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Kinetic method for the evaluation of Iyate ions activities in two-component protogenic solvents has been discussed. Spectral methods for the measurement of equilibria between alkoxide and hydroxide ions have been compared. A correlation between dissociation constants of water and of weak organic acids in solvent mixtures has been found. By means of this correlation, ratios of Iyate ions activities in water-ethanol and water-2-propanol mixtures have been calculated. These activity ratios, together with the known composition of reaction products, have been used to evaluate the selectivity of the neutral and alkaline solvolysis of phthalic anhydride and benzyl chloride in solvent mixtures quoted above.

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Effect of medium on dissociation of carboxylic acids

Cited by 10 publications

References 0 publications

Dissociation, tautomerism and electroreduction of xanthene and sulfonephthalein dyes inN,N‐dimethylformamide and other solvents

Dissociation, tautomerism and electroreduction of xanthene and sulfonephthalein dyes inN,N‐dimethylformamide and other solvents

Inline Raman Spectroscopy and Indirect Hard Modeling for Concentration Monitoring of Dissociated Acid Species

Ratio of lyate ions activities in two-components protogenic solvents

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