Acids In Nonaqueous Solutions Research Articles

A comprehensive study on the impact of the substituent on pKa of phenylboronic acid in aqueous and non-aqueous solutions: A computational approach

The acid dissociation constant (pKa) is the fundamental physicochemical properties required to understand the structure and reactivity of boronic acid-based material as a sensor that identifies carbohydrates. However, there is a lack of comprehensive study on the impact of the substituent on the pKa of monosubstituted phenylboronic acid in aqueous and non-aqueous solutions. In this work, extensive experimental data on the pKa of monosubstituted phenylboronic acid in an aqueous solution was reviewed and compared in terms of accuracy. In addition, computational, were used to predict and investigate the impact of the substituent on the pKa for a series of monosubstituted phenylboronic acid in an aqueous solution at the molecular level. Good agreement was observed between predicted and literature pKa values of monosubstituted phenylboronic acid in the aqueous solution. While some deviations exist, predominantly with fluorine-containing phenylboronic acid, the COSMO-RS model is proficient at predicting the pKa of boronic acid in an aqueous solution with the accuracy of ±1.5 pKa. Subsequently, the model was used to predict the pKa of boronic acid in the non-aqueous solution, which data is not available in the literature. Furthermore, an excellent relationship is observed between the acidity of para-substituted, and to some extent, meta-substituted phenylboronic acid with the atomic charge of acidic hydrogen calculated using Natural Bond Orbital (NBO) Population Analysis. In contrast, the steric hindrance and the existence of other molecular forces might influence the acidity of ortho-substituted phenylboronic acid. The gathered information in this work could be of benefit for the understanding of the acidity of the boronic acid-based materials not only as a sensor but also in many diverse areas.

Determination of Trace Amounts of Hydrofluoric Acid in Non-Aqueous Solutions by the Coulometric Titration Method.

For monitoring of trace amounts of hydrofluoric acid in the organic fluorine chemical industry, a facile method for determination of the hydrofluoric acid in an ethanol solution of lithium chloride, by coulometric titration, was proposed. Relying on homemade acid–base coulometric autotitrator, the electrolyte was 0.50 mol·L−1 LiCl ethanol solution and the constant current intensity was 0.2–2 mA. As for the working electrode pair, a platinum plate was used as a working electrode, and a platinum wire was used as an auxiliary electrode. The indicating electrode was the pH composite glass electrode and the titration endpoint was pH 5.50. The results showed that the relative standard deviation was below 2.0%, as the content of the hydrofluoric acid was between 2 μg to 100 μg. The recovery rate was 99.0–102.0%. This proposed route has the advantages of simplicity, convenience, quickness, accuracy, and automation, which can be applied to the accurate determination of trace amounts of hydrofluoric acid, in non-aqueous solutions.

NMR and luminescence spectroscopy study of the formation of mixed europium β-diketonate complexes with trifluoroacetic acid in nonaqueous solutions

The ligand substitution in Eu(AA)3 · Phen-CDCl3-TFA systems, where AA is acetylacetone, Phen is 1,10-phenanthroline, and TFA is trifluoroacetic acid was studied at various molar ratios (m) of competing ligands (m = TFA/AA) using NMR (1H, 19F) and luminescence spectroscopy. The formation of mixed Eu(AA)2(TFA) · Phen and Eu(AA)(TFA)2 · Phen complexes in the resultant solutions was attested. The luminescence spectra were studied. The competitive capacity of TFA was ascertained to be higher than that of AA. Depending on the m value, the substitution of acido ligands was shown to occur successively according equations Eu(AA)3 · Phen + (TFA)n = Eu(AA)3 − n(TFA)n · Phen + (AA)n (n = 1, 2, 3).

IEF-PCM Calculations of Absolute pKa for Substituted Phenols in Dimethyl Sulfoxide and Acetonitrile Solutions

Absolute (nonrelative) pKa calculations for substituted phenols were carried out in nonaqueous media, demonstrating the predictive power of the integral equation formalism PCM method with a mean unsigned error of 0.6 pKa units for DMSO and 0.7 pKa units for MeCN at the B3LYP/6-31+G** level of theory combined with the scaled B3LYP/6-311+G** gas-phase data. At the same time, the correlation between the calculated and experimental pKa values yielded the value of the linear regression slope very close to unity for both DMSO and MeCN. Computation of pKa of neutral acids in nonaqueous solutions with a reasonable precision obviously depends on carefully tuned cavities, optimized for nonaqueous solutions. The ability of continuum solvation model to compensate charge escape from the cavity, which is prominent in the case of anions, is also required. And finally, good quality gas-phase data is essential to achieve required pKa precision.

Nonaqueous Solution Studies on the Protonation Equilibria of some Phenolic Acids

The protonation equilibria for some phenolic acids in nonaqueous solutions have been studied by pH-potentiometry. The dissociation constants, pKa, of these phenolic acids and the thermodynamic functions, ΔGo,ΔHo and ΔSo, for the successive and overall protonation processes of these phenolic acids have been derived at different temperatures in three different mixtures of water and dioxane (mole fractions of dioxane were 0.083, 0.174 and 0.33). Titrations were also carried out in (water + dioxane) with ionic strengths of 0.15, 0.20 and 0.25 mol⋅dm−3 NaNO3, and the resulting dissociation constants are reported. A detailed thermodynamic analysis of the effects of organic solvent, dioxane, temperature and ionic strength on the protonation processes of phenolic acids is presented and discussed to determine the factors which control these processes.

Use of the electrical conductivity method to investigate the acid properties of heteropoly acids in nonaqueous solutions

1. The authors measure the electrical conductivities of heteropoly acids (HPA) of the compositions H3PMo12O40, H4PMo 11 VI MoVO40, H4PMo11VO40, H4SiMo12O40 and H4SiW12O40 in ethanol and acetone at 25°C. In the concentration range 10−5−10−3 mole/liter, all the HPA are partly dissociated 2−1 electrolytes; dissociation to the third and fourth degree is not manifested. 2. Using the Fuoss-Edelson method, they calculate the thermodynamic dissociation constants K2 and the limiting mobilities of the HPA.

Polarography of α-Keto Acids in Aqueous and Nonaqueous Solutions

Abstract Phenylglyoxylic acid (I), phenylpyruvic acid (II), and pyruvic acid (III) were polarographically studied in buffer solutions and in DMF. Their reduction waves were reinvestigated in a wider pH range. Cyclic voltammetry showed that most electrode reactions of these acids in acidic pH are irreversible. pH-Dependence of E1⁄2 and limiting current was studied. The observed decrease of the limiting currents of II and III in the strongly alkaline region was attributed to the dissociation of their corresponding enol forms. The i-E curves of these acids in DMF showed successive poorly-defined reduction waves, while those of the corresponding tetraethylammonium salts (TEA salts) were found to be much simpler in shape. A small oxidation wave was also observed with TEA salts of II and III, suggesting the presence of the enol form in DMF. The reduction products of I and its salt in DMF were studied by means of controlled potential electrolysis and NMR-spectroscopy. The electrode reaction mechanism of α-keto acids in nonaqueous solution is discussed, emphasizing the role of the free acid form as a proton-donor and the formation of a radical anion followed by a disproportionation reaction.

Influence of sodium perchlorate as conductive salt for coulometric determinations on the shape of electrometric titration curves of acids in non-aqueous solutions

Influence of sodium perchlorate as conductive salt for coulometric determinations on the shape of electrometric titration curves of acids in non-aqueous solutions

Application of bismuth indicating system for coulometric determination of oxalic and succinic acids in nonaqueous solutions

Coulometric determinations of the mentioned acids alone and in mixture, in the presence of sodium perchlorate as conductive salt, were performed in a number of organic solvents applying the bismuth electrode-pair biamperometry and as reference glass/calomel electrode potentiometry. It appeared that also in this case, the bismuth indicating system could be successfully applied.

Application of an indicating system of bismuth electrodes for the determination of organic bases and acids in nonaqueous solutions

Tertiary amines and salts of organic acids have been titrated by means of perchloric acid applying a biamperometric indicating system consisting of a polarised or unpolarised pair of bismuth electrodes. Also, mono- and polycarboxylic acids, alone and in mixtures, have been determined with a strong base using the same end-point detection technique. The results obtained are in good agreement with those of potentiometry or catalytic thermometry.

The conductometric titration of carboxylic and phenolic acids in non-aqueous solutions: Study of the titration of dibasic acids

An experimental study has been made of the conductoinetric titration of dibasic acids in non-aqueous solvents. The factors governing the shape of the titration curve and hence determining the accuracy of the analysis of these compounds are discussed, and the conditions are given under which optimum results are obtained.

The conductometric titration of carboxylic and phenolic acids in non-aqueous solutions: The resolution of acid mixtures and some practical applications

A detailed study has been made of non-aqueous conductometric titrations suitable for the resolution of acid mixtures. The optimum conditions for the various determinations with respect to base and solvent are extensively discussed. The applications include determinations of diphen-ylolpropane, naphthenic acids, perchloric acid and mixtures containing sulphuric acid.

Titration of Acids in Nonaqueous Solutions with Tetrabutylammonium Hydroxide. Reaction of Solvents with Strong Acids

Titration of Acids in Nonaqueous Solutions with Tetrabutylammonium Hydroxide. Reaction of Solvents with Strong Acids

The conductometric titration of carboxylic and phenolic acids in non-aqueous solutions : Preliminary experiments

The present study deals with the conductometric titration of weak organic acids and alkylphenols in non-aqueous solution. It is shown that the results are highly dependent on the bases and solvents used. A detailed account is given of experience gained with this method. A series of successful titrations of some types of acids is described in order to illustrate the versatility of conductometric titration.

Tetrabutylammonium Hydroxide as Titrant for Acids in Nonaqueous Solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTetrabutylammonium Hydroxide as Titrant for Acids in Nonaqueous SolutionsR. H. Cundiff and P. C. MarkunasCite this: Anal. Chem. 1956, 28, 5, 792–797Publication Date (Print):May 1, 1956Publication History Published online1 May 2002Published inissue 1 May 1956https://doi.org/10.1021/ac60113a004RIGHTS & PERMISSIONSArticle Views819Altmetric-Citations130LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (614 KB) Get e-Alerts Get e-Alerts