Variation of acidity constants and pH values of some organic acids in water—2-propanol mixtures with solvent composition. Effect of preferential solvation

Bosch, Elisabeth; Ràfols, Clara; Rosés, Martı́

doi:10.1016/0003-2670(94)00435-o

Cited by 51 publications

(29 citation statements)

References 19 publications

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“…in methanol/water, ethanol/water, isopropanol/water, tetrahydrofuran/water, and acetonitrile/water systems; Bosch et al, 1995;Cox, 2015;Rosés and Bosch, 2002). The findings also agree with intermolecular attraction theory, in that organic mixtures are poor solvators of ions compared to water (Cox, 2015;Sarmini and Kenndler, 1999 Cox, 2015;Sarmini and Kenndler, 1999).…”

Section: Resultssupporting

confidence: 77%

“…In 98% IPA, the pKa values of organic acids increase to such an extent that they no longer protonate bases such as nicotine in approximately neutral solutions. The pKa of acetic acid increases from 4.75 in water to 11.35 in pure IPA (Bosch et al, 1995). The pKa of nicotine in IPA is not precisely known, but the following NMR data demonstrates that acetic acid does not protonate nicotine at a 1:1 concentration in a 95% IPA solution.…”

Section: Discussionmentioning

confidence: 85%

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Acid-Base Equilibria in Organic-Solvent/Water Mixtures and Their Relevance to Gas/Particle Partitioning in the Atmosphere and in Tobacco Smoke

DeGagne¹

2000

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Acid-base equilibria in organic particulate matter (PM) are poorly understood, but have important implications for air quality and public health. First, acid-base reactions in organic particulate matter affect the gas/particle partitioning of organic compounds in the atmosphere, and these processes are not currently represented in atmospheric and climate change models. Second, the acid-base balance of tobacco smoke affects the amount of nicotine absorbed by the smoker, and a greater understanding of this balance would help to relate cigarette smoke composition to the addictive properties of cigarettes. This work presents data related to both air quality and tobacco smoke modeling.The gas/particle partitioning behavior of organic acids and bases is highly dependent on acid-base equilibria and speciation between neutral and ionic forms, because ionic compounds do not volatilize. Descriptions of acid dissociation behavior in atmospheric PM have, to date, focused primarily on phases in which the solvent is water; however, atmospheric PM may include up to 90% organic matter. Data is presented here describing the acid dissociation behavior of organic acids and protonated amines in organic/aqueous mixtures (chosen to approximate the characteristics of organic PM) with varying levels of water content. In such mixtures, the preferential solvation of ions and neutral molecules (by the aqueous portion or the organic portion, respectively) affects the acid-base equilibria of the solutes. It is demonstrated that neutralization reactions between acids and bases that create ions are likely to have non-negligible effects on gas/particle partitioning under certain atmospheric conditions. Thus, including acid-base reactions in organic gas/particle partitioning models could result in a greater proportion of acidic and ii basic compounds partitioning to the particulate phase. In addition, the acid dissociation constants (pKa values) of atmospherically-relevant acids and bases vary with water content. Specifically, as water content increases, the pKa values of organic acids decrease dramatically, while the pKa values of protonated amines changes only slightly. This situation can result in drastically different speciations and partitioning behavior depending on water content. This second part of this work reports some of the data needed to develop an acid-base balance for tobacco smoke PM using electroneutrality as a governing principle. Five brands of cigarettes were sampled and the smoke PM extracted. Cations (sodium, potassium, and ammonia) and anions (organic acids, nitrate, nitrite, and chloride) were measured using ion chromatography. Ammonia and organic acids were also re-measured after the acidification of the sample in order to determine whether "bound" forms of these compounds exist in cigarette PM. Weak acids were determined by acid-base titration to determine whether or not all of the weak acids (including organic acids) had been accounted for by the ion chromatography. Weak bases were also determined by acid-base...

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Section: Resultssupporting

confidence: 77%

Section: Discussionmentioning

confidence: 85%

Acid-Base Equilibria in Organic-Solvent/Water Mixtures and Their Relevance to Gas/Particle Partitioning in the Atmosphere and in Tobacco Smoke

DeGagne¹

2000

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“…For the sake of simplicity, this solvent system is usually considered to be a binary system consisting pure methanol and water. However, Katz et al in 1986 [4,5] and after that Bosch et al [6,7] showed that binary concept of methanol-water mixtures does not comfort to the solute distribution theory and acid-base studies. As a result of strong hydrogen bonding, Katz et al [4,5] considered methanol-water mixtures to consist of water associated with itself, methanol associated with itself and a methanol-water association cluster that is in equilibrium with the pure water and methanol.…”

Section: Introductionmentioning

confidence: 96%

“…By using the same data as Katz et al they found the logarithm of the formation constant of MW to be 0.8 on a mole fraction scale. The solutesolvent and solvent-solvent interactions in methanol-water mixtures have also been studied by Roses, Bosch and coworkers using solvatochromic methods [2,[6][7][8][9][10]. They defined and determined the values of preferential solvation parameters for different solute indicators.…”

Section: Introductionmentioning

confidence: 98%

Characterization and prediction of solute properties in methanol–water association by chemometrics analysis of solvation data

Hemmateenejad

2005

Journal of Chemometrics

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Methanol-water binary mixtures have been characterized as a ternary or quaternary system composed of unassociated methanol (M) and water (W) and one or two methanol-water complex (MW). Identification of the methanol-water association was performed by chemometrics analysis of some solvent-related properties of binary methanol-water mixtures with compositions between 0 and 100% volume percent of methanol. Abstract factor analysis of the solvation data identified three chemical species in the solvent mixtures that can be attributed to the pure methanol and water solvents and a MW association. The stoichiometric molar ratio of the W:M associate was investigated by the multivariate curve resolution-alternative least squares (MCR-ALS) of the solvation data and the resulted concentration profiles of the solvent species implied a 1:1 molar ratio for the M:W association. The equilibrium constant of the formation of the M-W association was determined by MCR-ALS and iterative rank annihilation factor analysis (RAFA) to be equal to 13.72. The solvation data of the pure M-W cluster was calculated by target factor analysis (TFA) procedure. Higher hydrogen-bond basicity and lower hydrogen-bond acidity was obtained for the MW solvent in comparison with both the M and W solvents. The proposed model was employed to calculate the acidity constant and HPLC capacity factors of some solutes in the MW cluster. Interestingly, the solutes were found to be stronger acid in relative to pure methanol and water. Finally, the specific solute-solvent interactions and preferential solvation of the solutes were explained by the nonmodeled solute-related data.

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“…In fact, Roses and co-workers [20][21][22] and Takayanagi and co-workers 23 have studied this behavior, which is probably related to the association of several factors, such as auto-protolysis and solute-solvent/solventsolvent interactions. Figure 8 and its inset show that, above 40% of water, the RLS intensity for magnesium and zinc chlorophylls decreases abruptly, reaching a minimum light scattering from approximately 60% of water in ethanol/water mixture.…”

Section: Resultsmentioning

confidence: 99%

Metallochlorophylls of magnesium, copper and zinc: evaluation of the influence of the first coordination sphere on their solvatochromism and aggregation properties

Moreira¹,

Lima²,

Soares³

et al. 2009

J. Braz. Chem. Soc.

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No presente estudo, o papel de diferentes centros metálicos (magnésio, zinco e cobre) sobre o caráter hidrofílico de metaloclorofilas foi avaliado. O solvatocromismo, assim como o processo de agregação para esses compostos, em misturas água/etanol foram avaliados usando medidas de fluorescência e de espalhamento de luz ressonante (ELR), visando caracterizar o comportamento desses compostos. Independente da metaloclorofila estudada, a presença de ao menos 60% de água resulta em incremento considerável na emissão de fluorescência apresentada por esses compostos. Isso, provavelmente, é uma conseqüência direta de uma menor agregação, o que é confirmado pelos resultados de ELR. Adicionalmente, os resultados sugerem que as clorofilas de magnésio e de zinco devem ser promissores agentes fototerapêuticos para emprego em Terapia Fotodinâmica.In this study the role of different metal centers (magnesium, zinc and copper) on the enhancement of the hydrophilic character of metallochlorophylls, was evaluated. The solvatochromism as well as the aggregation process for these compounds in water/ethanol mixtures at different volume ratios were evaluated using Fluorescence, and Resonant Light Scattering (RLS) measurements, aiming to characterize the behavior of these compounds. Independently on the studied metallochlorophyll, the presence of at least 60% of water results in a considerable increase in the fluorescence emission, probably a direct consequence of a lower aggregation of these compounds, which is confirmed by the results from RLS measurements. Additionally, the results suggest that magnesium and zinc chlorophyll should be promising phototherapeutic agents for Photodynamic Therapy.

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Variation of acidity constants and pH values of some organic acids in water—2-propanol mixtures with solvent composition. Effect of preferential solvation

Cited by 51 publications

References 19 publications

Acid-Base Equilibria in Organic-Solvent/Water Mixtures and Their Relevance to Gas/Particle Partitioning in the Atmosphere and in Tobacco Smoke

Acid-Base Equilibria in Organic-Solvent/Water Mixtures and Their Relevance to Gas/Particle Partitioning in the Atmosphere and in Tobacco Smoke

Characterization and prediction of solute properties in methanol–water association by chemometrics analysis of solvation data

Metallochlorophylls of magnesium, copper and zinc: evaluation of the influence of the first coordination sphere on their solvatochromism and aggregation properties

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