Ionic equilibria in aqueous organic solvent mixtures the dissociation constants of acids and salts in tetrahydrofuran/water mixtures

Muinasmaa, Urmas; Ràfols, Clara; Bosch, Elisabeth; Rosés, Martı́

doi:10.1016/s0003-2670(96)00516-8

Cited by 33 publications

(10 citation statements)

References 34 publications

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“…However, determination of pK a in mobile phases commonly used in RP-HPLC is not trivial because of the presence of organic solvents, which can affect both the pK a of buffer compounds (leading to pH changes in the mobile phase) and that of the solute itself [6,7]. In general, the pK a of acids increases as organic solvent concentration increases, whereas that of bases decreases compared with the value in aqueous solution [8][9][10][11][12][13][14]. The pK a of acid silanol groups on the surface is likely to be affected in a similar fashion.…”

Section: Introductionmentioning

confidence: 99%

Determination of ionisation constants of organic bases in aqueous methanol solutions using capillary electrophoresis

Buckenmaier

McCalley

Euerby

2004

Journal of Chromatography A

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Section: Introductionmentioning

confidence: 99%

Determination of ionisation constants of organic bases in aqueous methanol solutions using capillary electrophoresis

Buckenmaier

McCalley

Euerby

2004

Journal of Chromatography A

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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: 98%

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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“…However, it was found that the conversion of xylose decreased by 5 mol% in the presence of THF than that in a single water solvent. This was possibly due to the lower dielectric constant of H 2 O/THF (ε = 40) than that of pure water (ε = 78.5 at 25 • C) which decreased the acidity of reactions system (Critchfield et al, 1953;Muinasmaa et al, 1997). In final, furfural with 56.6 mol% of yield and 62.3 mol% of selectivity was obtained in this H 2 O/THF/MIBK-high-pressure CO 2 system (50 bar).…”

Section: Lignin Solubilization and Depolymerization In H 2 O/thf Systemmentioning

confidence: 89%

The Roles of H2O/Tetrahydrofuran System in Lignocellulose Valorization

Zhang

et al. 2020

Front. Chem.

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Lignocellulosic biomass as a potential alternative to fossil resource for the production of valuable chemicals and fuels has attracted substantial attention, while reducing the recalcitrance of lignocellulosic biomass is still challenging due to the complex and cross-linking structure of biomass. Solvent system plays important roles in the pretreatment of lignocellulose, enabling the transformation of solid biomass to liquid fluid with better mass and heat transfer, as well as in the selective formation of target products. In particular, H 2 O/tetrahydrofuran (H 2 O/THF) system has recently been widely applied in lignocellulose valorization, which has been proved to exhibit outstanding efficiency for the conversion of lignocellulose, solubilization of the intermediates and products, and shifting reaction equilibrium, thereby significantly improving the yield and selectivity of target products, as well as the full utilization of lignocellulose. In addition, THF shows low toxicity, and is known as a renewable solvent which can be produced from bio-derived chemicals. Herein, this review concentrates on the advances of H 2 O/THF system in lignocellulose valorization in recent years. Several aspects relative to the roles of H 2 O/THF system are discussed as follows: the pretreatment of lignin, conversion of hemicellulose and cellulose components in lignocelluloses, and the promoting formation of valuable chemicals like furfural, 5-hydroxymethyl furfural (HMF), levulinic acid, and so on, as well as the inhibiting role in humins formation. This review might provide useful information for the design of effective solvent system in full utilization of lignocellulosic biomass.

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Ionic equilibria in aqueous organic solvent mixtures the dissociation constants of acids and salts in tetrahydrofuran/water mixtures

Cited by 33 publications

References 34 publications

Determination of ionisation constants of organic bases in aqueous methanol solutions using capillary electrophoresis

Determination of ionisation constants of organic bases in aqueous methanol solutions using capillary electrophoresis

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

The Roles of H2O/Tetrahydrofuran System in Lignocellulose Valorization

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