Página 1 dos resultados de 470 itens digitais encontrados em 0.018 segundos

Solvation simplified

EL SEOUD, Omar A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.32%
The effects of solvents on chemical phenomena is complex because there are various solute-solvent interaction mechanisms. Solvatochromism refers to the effects of solvents on the spectra of probes. The study of this phenomenon sheds light on the relative importance of the solvation mechanisms. Solvation in pure solvents is quantitatively analyzed in terms of a multi-parameter equation. In binary solvent mixtures, solvation is analyzed by considering the organic solvent, S, water, W, and a 1:1 hydrogen bonded species (S-W). The applications of solvatochromism to understand distinct chemical phenomena, reactivity and swelling of cellulose, is briefly discussed.; (FAPESP) São Paulo Research Foundation; CNPq National Council for Scientific and Technological Research

Understanding solvation

SEOUD, Omar A. El
Fonte: INT UNION PURE APPLIED CHEMISTRY Publicador: INT UNION PURE APPLIED CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.42%
The effects of solvents on different chemical phenomena, including reactivity, spectroscopic data, and swelling of biopolymers can be rationalized by use of solvatochromic probes, substances whose UV-vis spectra, absorption, or emission are sensitive to the properties of the medium. Thermo-solvatochromism refers to the effect of temperature on solvatochromism. The study of both phenomena sheds light on the relative importance of the factors that contribute to solvation, namely, properties of the probe, those of the solvent (acidity, basicity, dipolarity/polarizability, and lipophilicity), and the temperature. Solvation in binary solvent mixtures is complex because of ""preferential solvation"" of the probe by some component of the mixture. A recently introduced solvent exchange model is based on the presence in the binary solvent mixture of the organic component (molecular solvent or ionic liquid), S, water, W, and a 1:1 hydrogen-bonded species (S-W). Solvation by the latter is more efficient than by its precursor solvents, due to probe-solvent hydrogen-bonding and hydrophobic interactions; dimethyl sulfoxide (DMSO)-W is an exception. Solvatochromic data are employed in order to explain apparently disconnected phenomena, namely, medium effect on the pH-independent hydrolysis of esters...

Thermodynamic Stabillity of Hydrogen-Bonded Systems in Polar and Nonpolar Environments

PASALIC, Hasan; AQUINO, Adelia J. A.; TUNEGA, Daniel; HABERHAUER, Georg; GERZABEK, Martin H.; Georg, Herbert de Castro; Moraes, Tatiane Faustino de; Coutinho, Kaline Rabelo; Canuto, Sylvio Roberto Accioly; LISCHKA, Hans
Fonte: JOHN WILEY & SONS INC Publicador: JOHN WILEY & SONS INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.42%
The thermodynamic properties of a selected set of benchmark hydrogen-bonded systems (acetic acid dimer and the complexes of acetic acid with acetamide and methanol) was studied with the goal of obtaining detailed information on solvent effects on the hydrogen-bonded interactions using water, chloroform, and n-heptane as representatives for a wide range in the dielectric constant. Solvent effects were investigated using both explicit and implicit solvation models. For the explicit description of the solvent, molecular dynamics and Monte Carlo simulations in the isothermal isobaric (NpT) ensemble combined with the free energy perturbation technique were performed to determine solvation free energies. Within the implicit solvation approach, the polarizable continuum model and the conductor-like screening model were applied. Combination of gas phase results with the results obtained from the different solvation models through an appropriate thermodynamic cycle allows estimation of complexation free energies, enthalpies, and the respective entropic contributions in solution. Owing to the strong solvation effects of water the cyclic acetic acid dimer is not stable in aqueous solution. In less polar solvents the double hydrogen bond structure of the acetic acid dimer remains stable. This finding is in agreement with previous theoretical and experimental results. A similar trend as for the acetic acid dimer is also observed for the acetamide complex. The methanol complex was found to be thermodynamically unstable in gas phase as well as in any of the three solvents. (C) 2010 Wiley Periodicals...

Solvatação em solventes puros e misturas binárias: fundamentos e aplicações; Solvation in pure solvents and binary mixtures: fundamentals and applications

Silva, Priscilla Leandro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/03/2011 PT
Relevância na Pesquisa
36.39%
Este trabalho visou compreensão da solvatação em solventes puros e misturas binárias, e aplicar as informações obtidas para analisar o efeito de solventes na síntese de líquido iônico, e na dependência das propriedades de filmes de acetatos de celulose, AC, sobre o grau de substituição do éster. Para a compreensão da solvatação utilizou-se compostos (sondas solvatocrômicas) cujos espectros Uv-Vis são sensíveis às propriedades do meio. Juntamente com tais sondas, foram usadas outras duas ferramentas: (i) Modelo de solvatação preferencial; proposto por nosso grupo e que descreve a composição da camada de solvatação da sonda, considerando a existência de um "agregado" água - solvente orgânico. (ii)Correlações multi-paramêtricas de energia livre de solvatação; que correlacionam uma propriedade dependente do meio com as propriedades dos solventes e suas misturas. Primeiramente, estudamos a solvatação de pares de sondas que possuíam pKas semelhantes e lipofilicidades diferentes em solventes próticos. Concluiu-se que a acidez e a dipolaridade/polarizabilidade dos solventes são as propriedades mais importantes. As conclusões foram corroboradas por cálculos teóricos, que mostraram a relação entre as características estruturais da sonda e suas susceptibilidades às propriedades do meio. O mesmo conjunto de sondas foi usado no estudo de misturas água-solventes próticos. Neste...

Influência de parâmetros moleculares em funções de correlação temporal na dinâmica de solvatação mecânica; Influence of molecular parameters on time correlations functions of mechanical solvation dynamics

Martins, Marcio Marques
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
36.36%
No presente trabalho descrevemos nossos resultados relativos à investigação da dinâmica de solvatação mecânica por meio de simulações por dinâmica molecular, respeitando o regime da resposta linear, em sistemas-modelo de argônio líquido com um soluto monoatômico ou diatômico dissolvido. Estudamos sistematicamente a influência dos parâmetros moleculares dos solutos (tamanho, polarizabilidade) e da densidade frente a vários modelos de solvatação. Funções de Correlação Temporal da Energia de Solvatação foram calculadas com relação à correlações de n-corpos (n = 2; 3) distinguindo interações repulsivas e atrativas para ambos os sistemas líquidos. Também obtivemos segundas derivadas temporais dessas funções referindo-se à parcelas translacionais, rotacionais e roto-translacionais na solução do diatômico. Encontramos que funções de correlação temporal coletivas podem ser razoavelmente bem aproximadas por correlações binárias a densidades baixas e, a densidades altas, correlações ternárias tornam-se mais importantes produzindo um descorrelacionamento mais rápido das funções coletivas devido a efeitos de cancelamento parciais. As funções de correlação para interações repulsivas e atrativas exibem comportamentos dinâmicos independentes do modelo de solvatação devido a fatores de escalonamento linear que afetam apenas as amplitudes das dessas funções de correlação temporal. Em geral...

Solvation simplified

El Seoud,Omar A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
Relevância na Pesquisa
36.32%
The effects of solvents on chemical phenomena is complex because there are various solute-solvent interaction mechanisms. Solvatochromism refers to the effects of solvents on the spectra of probes. The study of this phenomenon sheds light on the relative importance of the solvation mechanisms. Solvation in pure solvents is quantitatively analyzed in terms of a multi-parameter equation. In binary solvent mixtures, solvation is analyzed by considering the organic solvent, S, water, W, and a 1:1 hydrogen bonded species (S-W). The applications of solvatochromism to understand distinct chemical phenomena, reactivity and swelling of cellulose, is briefly discussed.

Solvation effects are responsible for the reduced inhibitor affinity of some HIV-1 PR mutants.

Sussman, F.; Villaverde, M. C.; Davis, A.
Fonte: Cold Spring Harbor Laboratory Press Publicador: Cold Spring Harbor Laboratory Press
Tipo: Artigo de Revista Científica
Publicado em /05/1997 EN
Relevância na Pesquisa
46.09%
The formulation of HIV-1 PR inhibitors as anti-viral drugs has been hindered by the appearance of protease strains that present drug resistance to these compounds. The mechanism by which the HIV-1 PR mutants lower their affinity for the inhibitor is not yet fully understood. We have applied a modified Poisson-Boltzmann method to the evaluation of the molecular interactions that contribute to the lowering of the inhibitor affinity to some polar mutants at position 82. These strains present drug resistance behavior and hence are ideally suited for these studies. Our results indicate that the reduction in binding affinity is due to the solvation effects that penalize the binding to the more polar mutants. The inhibitor binding ranking of the different mutants can be explained from the analysis of the different components of our free energy scoring function.

Towards Accurate Microscopic Calculation of Solvation Entropies: Extending the Restraint Release Approach to Studies of Solvation Effects

Singh, Nidhi; Warshel, Arieh
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 21/05/2009 EN
Relevância na Pesquisa
36.52%
The evaluation of the solvation entropies is a major conceptual and practical challenge. On the one hand, it is interesting to quantify the factors that are responsible for the solvation entropies in solutions, while on the other, it is essential to be able to assess the contributions of the solvation entropies to the binding free energies and related properties. In fact, the solvation entropies are neglected in almost all the studies of the binding entropies. The main problem is that widely used approaches, such as the quasiharmonic (QH) approximation do not provide reliable results particularly, in cases of shallow potential and multidimensional surfaces while brute force evaluations of the entropic effects by simulating temperature dependence of the free energy converges very slowly. This paper addresses the above issue by starting with an analysis of the factors that are responsible for the negative solvation entropy of ions, showing that it is not due to the change in the solvent vibration modes or to the solvent force constant but to the changes in the solvent configurational space upon change in the solute charges. We begin by clarifying that when one deals with aqueous solutions, it is easy to evaluate the corresponding entropic effect by the Langevin dipole(LD) treatment. However...

Association Thermodynamics and Conformational Stability of β-Sheet Amyloid β(17-42) Oligomers: Effects of E22Q (Dutch) Mutation and Charge Neutralization

Blinov, Nikolay; Dorosh, Lyudmyla; Wishart, David; Kovalenko, Andriy
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em 20/01/2010 EN
Relevância na Pesquisa
36.31%
Amyloid fibrils are associated with many neurodegenerative diseases. It was found that amyloidogenic oligomers, not mature fibrils, are neurotoxic agents related to these diseases. Molecular mechanisms of infectivity, pathways of aggregation, and molecular structure of these oligomers remain elusive. Here, we use all-atom molecular dynamics, molecular mechanics combined with solvation analysis by statistical-mechanical, three-dimensional molecular theory of solvation (also known as 3D-RISM-KH) in a new MM-3D-RISM-KH method to study conformational stability, and association thermodynamics of small wild-type Aβ17–42 oligomers with different protonation states of Glu22, as well the E22Q (Dutch) mutants. The association free energy of small β-sheet oligomers shows near-linear trend with the dimers being thermodynamically more stable relative to the larger constructs. The linear (within statistical uncertainty) dependence of the association free energy on complex size is a consequence of the unilateral stacking of monomers in the β-sheet oligomers. The charge reduction of the wild-type Aβ17–42 oligomers upon protonation of the solvent-exposed Glu22 at acidic conditions results in lowering the association free energy compared to the wild-type oligomers at neutral pH and the E22Q mutants. The neutralization of the peptides because of the E22Q mutation only marginally affects the association free energy...

Role of Solvation Effects in Protein Denaturation: From Thermodynamics to Single Molecules and Back

England, Jeremy L.; Haran, Gilad
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/2011 EN
Relevância na Pesquisa
46.24%
Protein stability often is studied in vitro through the use of urea and guanidinium chloride, chemical cosolvents that disrupt protein native structure. Much controversy still surrounds the underlying mechanism by which these molecules denature proteins. Here we review current thinking on various aspects of chemical denaturation. We begin by discussing classic models of protein folding and how the effects of denaturants may fit into this picture through their modulation of the collapse, or coil-globule transition, which typically precedes folding. Subsequently, we examine recent molecular dynamics simulations that have shed new light on the possible microscopic origins of the solvation effects brought on by denaturants. It seems likely that both denaturants operate by facilitating solvation of hydrophobic regions of proteins. Finally, we present recent single-molecule fluorescence studies of denatured proteins, the analysis of which corroborates the role of denaturants in shifting the equilibrium of the coil-globule transition.

Modelling specific ion effects with the continuum solvent

Duignan, Timothy Thomas
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD)
EN
Relevância na Pesquisa
36.45%
Electrolyte solutions play a central role in many processes from industry to biology. Understanding and building predictive models of their properties has therefore been a fundamental goal of physical chemistry from its beginnings. The challenge remains. In this thesis I outline a continuum solvent model of univalent monatomic ions in water. This model calculates the free energy of: 1) a single ion in bulk, 2) of an ion approaching the air–water interface and 3) of two ions approaching each other. Its central advancements are to include quantitatively accurate ionic dispersion interaction energies, missing from classical theories, including the higher order multipole moment contributions to these interactions. It also includes the contribution from the cavity formation energy consistently, including the effect of changes in the cavity’s shape. Lastly, it uses a quantum mechanical treatment of the ions and provides satisfactory values for their size parameters. Because one consistent framework is used with the same assumptions to calculate the free energies in these three different situations the number of parameters can be minimised and the model can be properly tested. These three calculations can be used to reproduce experimental solvation free energies...

Estudo teórico de efeitos de solvatação do tetraidrofurano sobre um mecanismo modelo de Suzuki-Miyaura; Theoretical study of the effects of tetrahydrofuran's solvation over a Suzuki-Miyaura's model mechanism

Mauricio Chagas da Silva
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/02/2011 PT
Relevância na Pesquisa
46.39%
Utilizando a implementação do método da coordenada geradora discretizada nos orbitais atômicos, conjuntos de bases adaptados ao pseudopotencial de caroço SBKJC (conjuntos GBSMCS) foram desenvolvidos, validados e utilizados no estudo de possíveis efeitos de solvatação do tetraidrofurano sobre um mecanismo modelo de Suzuki-Miyaura. As metodologias de validação adotadas para os conjuntos GBSMCS foram os cálculos teóricos da afinidade por próton de sistemas atômicos e moleculares, iônicos e neutros, das entalpias de liquefação de alguns solventes orgânicos rotineiros e das entalpias de hidratação de 29 compostos orgânicos diversos. Nas etapas de validação, observou-se de uma maneira geral, uma boa relação entre custo e benefício na utilização dos conjuntos de bases GBSMCS, obteveram-se desvios médios por volta de 0 até 20 kJ.mol, nas propriedades estudadas. Com as metodologias propostas neste trabalho e com a utilização dos conjuntos GBSMCS, determinou-se o perfil potencial da reação modelo de Suzuki-Miyaura tanto em fase gasosa como em fase solvatada de tetraidrofurano. Não se observou efeitos significativos nas estruturas dos estados estacionários caracterizados e nem nas DrG para as etapas de adição-oxidativa...

Efectos de solvatación en agregados supramoleculares; Solvation effects in supramolecular aggregates

Pomata, Matías H.H.
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2010 SPA
Relevância na Pesquisa
46.2%
En la primera parte de esta tesis presentamos simulaciones de dinámica molecular sobre micelas inversas inmersas en ciclohexano. Consideramos tres interiores polares diferentes: agua (W), formamida (FM) y una mezcla equimolar de ambos solventes. En todos los casos, el surfactante utilizado fue bis(2-etilhexil)sulfoccinato de sodio (usualmente conocido como AOT). El radio inicial de las micelas fue deR ∼ 15 Å , mientras que los cocientes molares (w0=[fase polar]/[surfactante]) correspondientes fueronintermedios entre w0 = 4;3 para FM y w0 = 7 paraW. La forma global de las micelas se asemeja a elipsoidesdistorsionados, con una excentricidad media del orden de ∼ 0;75. Las correlaciones de densidadlocal dentro de las micelas muestran una solvatación preferencial de la especie iónica sodio por el agua,en contraposición con el comportamiento encontrado en mezclas equimolares en fase condensada. Comparadocon los resultados en fase condensada, los modos traslacionales y rotacionales de los solventesconfinados, exhiben una desaceleración importante, que se hace más notable en los movimientos rotacionales donde las escalas temporales características pueden ser hasta 50 veces más largas. también se discuten las modificaciones en la conectividad intramolecular...

Solvation Effects in Near-Critical Binary Mixtures

Onuki, Akira; Kitamura, Hikaru
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/05/2004
Relevância na Pesquisa
46.2%
A Ginzburg-Landau theory is presented to investigate solvation effects in near-critical polar fluid binary mixtures. Concentration-dependence of the dielectric constant gives rise to a shell region around a charged particle within which solvation occurs preferentially. As the critical point is approached, the concentration has a long-range Ornstein-Zernike tail representing strong critical electrostriction. If salt is added, strong coupling arises among the critical fluctuations and the ions. The structure factors of the critical fluctuations and the charge density are calculated and the phase transition behavior is discussed.; Comment: 12 pages, 8 figures, to be published in J. Chem. Phys

Modeling solvation effects in real-space and real-time within Density Functional Approaches

Delgado, Alain; Corni, Stefano; Pittalis, Stefano; Rozzi, Carlo Andrea
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/07/2015
Relevância na Pesquisa
46.2%
The Polarizable Continuum Model (PCM) can be used in conjunction with Density Functional Theory (DFT) and its time-dependent extension (TDDFT) to simulate the electronic and optical properties of molecules and nanoparticles immersed in a dielectric environment, typically liquid solvents. In this contribution, we develop a methodology to account for solvation effects in real-space (and real-time) (TD)DFT calculations. The boundary elements method is used to calculate the solvent reaction potential in terms of the apparent charges that spread over the Van der Waals solute surface. In a real-space representation this potential may exhibit a Coulomb singularity at grid points that are close to the cavity surface. We propose a simple approach to regularize such singularity by using a set of spherical Gaussian functions to distribute the apparent charges. We have implemented the proposed method in the Octopus code and present results for the electrostatic contribution to the solvation free energies and solvatochromic shifts for a representative set of organic molecules in water.; Comment: Version submitted to The Journal of Chemical Physics 10 pages, 7 Figures + supplemental material

Solvation Effects and Driving Forces for Protein Thermodynamic And Kinetic Cooperativity: How Adequate Is Native-Centric Topological Modeling?

Kaya, Huseyin; Chan, Hue Sun
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.09%
What energetic and solvation effects underlie the remarkable two-state thermodynamics and folding/unfolding kinetics of small single-domain proteins? To address this question, we investigate the folding and unfolding of a hierarchy of continuum Langevin dynamics models of chymotrypsin inhibitor 2. We find that residue-based additive G\=o-like contact energies, although native-centric, are by themselves insufficient for proteinlike calorimetric two-state cooperativity. Further native biases by local conformational preferences are necessary for proteinlike thermodynamics. Kinetically, however, even models with both contact and local native-centric energies do not produce simple two-state chevron plots. Thus a model protein's thermodynamic cooperativity is not sufficient for simple two-state kinetics. The models tested appear to have increasing internal friction with increasing native stability, leading to chevron rollovers that typify kinetics that are commonly referred to as non-two-state. The free energy profiles of these models are found to be sensitive to the choice of native contacts and the presumed spatial ranges of the contact interactions. Motivated by explicit-water considerations, we explore recent treatments of solvent granularity that incorporate desolvation free energy barriers into effective implicit-solvent intraprotein interactions. This additional feature reduces both folding and unfolding rates vis-\`a-vis that of the corresponding models without desolvation barriers...

Solvation effects on the band edge positions of photocatalysts from first principles

Ping, Yuan; Sundararaman, Ravishankar; Goddard, William A., III
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Article; PeerReviewed Formato: application/pdf; application/pdf
Publicado em 26/10/2015
Relevância na Pesquisa
46.45%
The band edge positions of photocatalysts relative to the redox potentials of water play an important role in determining the efficiency of photoelectrochemical cells. These band positions depend on the structure of the solid–liquid interface, but direct ab initio molecular dynamics calculations of these interfaces, while expected to be accurate, are too computationally demanding for high-throughput materials screening. Thus rapid theoretical screening of new photocatalyst materials requires simplified continuum solvation models that are suitable for treating solid–liquid interfaces. In this paper, we evaluate the accuracy of the recently developed CANDLE and SaLSA continuum solvation models for predicting solvation effects on the band positions of several well-studied surfaces [Si(111), TiO_2(110), IrO_2(110) and WO_3(001)] in water. We find that the solvation effects vary considerably, ranging from <0.5 eV for hydrophobic surfaces, 0.5–1 eV for many hydrophilic oxide surfaces, to ∼2 eV for oxygen-deficient surfaces. The solvation model predictions are in excellent agreement (within ∼0.1 eV) with ab initio molecular dynamics results where available, and in good agreement (within ∼0.2–0.3 eV) with experimental measurements. We also predict the energetics for surface oxygen vacancies and their effect on the band positions of the hydrated WO_3(001) surface...

Continuum level treatment of electronic polarization in the framework of molecular simulations of solvation effects

Leontyev, I V; Vener, M V; Rostov, Ivan; Basilevsky, M V; Newton, Marshall D
Fonte: American Institute of Physics (AIP) Publicador: American Institute of Physics (AIP)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.2%
The methodology for the computation of charge transfer reorganization energies was developed. The problem of a consistent separation of inertial and electronic polarization was also solved in a simple continuum electron transfer (ET) theories. The electrostatic component of experimental equilibrium solvation energies was obtained.

Preferential solvation of naringin in ethanol + water cosolvent mixtures according with the inverse Kirkwood-Buff integrals

Caviedes Rubio,Diego Iván; Sotomayor Pino,Reinaldo Gabriel; Delgado,Daniel Ricardo
Fonte: Revista Colombiana de Ciencias Químico - Farmacéuticas Publicador: Revista Colombiana de Ciencias Químico - Farmacéuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2015 EN
Relevância na Pesquisa
46.31%
The preferential solvation parameters, i.e., the differences between the local and bulk mole fractions of the solvents in solutions of naringin is derived from their solubility in binary solvent mixtures by means of the inverse Kirkwood-Buff integral (IKBI) method. According to IKBI method it is found that naringin is sensitive to solvation effects, so the preferential solvation parameter by ethanol δx1,3, is negative in waterrich and ethanol-rich mixtures but positive in compositions from 0.24 to 0.40 in mole fraction of ethanol. This could demonstrate the relevant role of hydrophobic hydration around the non-polar groups in the drug solvation in water-rich mixtures. Otherwise, in mixtures of intermediate co-solvent compositions, the drug is mainly solvated by ethanol, probably due to the basic behavior of the co-solvents; whereas, in ethanol-rich mixtures, the preferential solvation by water could be due to the acidic behavior of water.

Preferential solvation of acetaminophen in ethanol + water solvent mixtures according to the inverse Kirkwood-Buff integrals method

Delgado,Daniel Ricardo; Peña,Maria Angeles; Martínez,Feming
Fonte: Revista Colombiana de Ciencias Químico - Farmacéuticas Publicador: Revista Colombiana de Ciencias Químico - Farmacéuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 EN
Relevância na Pesquisa
46.39%
The preferential solvation parameters, i.e., the differences between the local mole fraction of solvents around the solute and those for the bulk co-solvent mixtures in solutions of acetaminophen in ethanol + water binary mixtures were derived from their thermodynamic properties by means of the inverse Kirkwood-Buff integrals (IKBI) method. It is found that acetaminophen is sensitive to solvation effects, so the preferential solvation parameter δxE,A, is negative in water-rich and ethanol-rich mixtures but positive in co-solvent compositions from 0.24 to 0.73 in mole fraction of ethanol. It is conjecturable that in water-rich mixtures the hydrophobic hydration around the aromatic ring and methyl group present in the drug plays a relevant role in the solvation. The more solvation by ethanol in mixtures of similar co-solvent compositions could be due mainly to polarity effects. Finally, the preference of this drug for water in ethanol-rich mixtures could be explained in terms of the bigger acidic behavior of water molecules interacting with the hydrogen-acceptor groups present in acetaminophen such as the carbonyl group.