Hydrophobic interactions solvophobic

Entropy-related adsorption, denoted hydrophobic sorption (or solvophobic interaction) is the partitioning of nonpolar organics out of the polar aqueous phase onto hydrophobic surfaces. Fig. 5.6 shows a schematic model of forces that contribute to the sorption of hydrophobic organics, relevant to the subsurface environment. 

Ben-Naim (1972b, c) has examined hydrophobic association using statistical mechanical theories of the liquid state, e.g. the Percus-Yevick equations. He has also examined quantitative aspects of solvophobic interactions between solutes using solubility data for ethane and methane. The changes in thermodynamic parameters can be calculated when two methane molecules approach to a separation of, 1-533 x 10-8 cm, the C—C distance in ethane, and the solvophobic quantities 8SI/i, s 2 and 8SiS2 can be calculated. In water (solvophobic = hydrophobic) 5si/i is more negative than in other solvents and decreases as the temperature rises both 8s iH%... 

Secondary binding forces are mainly classified into Coulomb forces, hydro-gen-bonding forces, van der Waals forces, charge transfer forces, exchange repulsion and hydrophobic interactions (Table 1). Besides these forces, there are other interactions such as ion-dipole and solvophobic interactions. 

Section 2.5.3 in Chapter 2 expounded upon the hydrophobic ion-pair concept The peculiarities of this association mode, not even likely in the Bjerrum s model, were elucidated. Electrostatic attraction is only part of the story and solvophobic interactions are crucial to rationalize experimental evidence that often runs counter to the pristine electrostatic description of the process. 

The research on aggregation of surfactants in nonaqueous, polar solvent systems can be motivated, mainly, with two different arguments. First, are the basic considerations of amphiphile aggregation involving a description of the hydrophobic interaction leading to, for example, micelle and liquid crystal formation. What can be learned from comparing water with other polar solvents Much work has been performed to elucidate those properties of the solvent that are essential in order to obtain a hydrophobic (or solvophobic ) interaction. Comparisons of critical micelle concentrations in different solvents with parameters characterizing the solvent are numerous in the literature [1,2],... 

A number of articles (Karger et al., 1976 Colin et al., 1983 Verzele and Dewaele, 1984) have examined the mechanisms of retention on the column. Hydrophobic, silano-philic and solvophobic interactions have been identified as important factors in the retention processes. It is likely that some or all of these interactions exist to varying degrees during a separation and the dominance of any one will depend on the experimental conditions. 

An important criterion is the solvent s capacity for solvophobic interactions, of which hydrophobic interactions are a specific case (Ray, 1971 see also Cramer, 1977 Klibanov et al., 1978 Tanford, 1978 Kauzmann, 1979 Hildebrand, 1979). According to this criterion, solvents can be grouped in the following three classes in decreasing order of solvolytic interactions, that is, of biphasic effectiveness ... 

In this chapter, we use the superscript HI mainly for hydrophobic interaction. Clearly, the quantities defined in (8.26) can also apply to any other solvent for which the term solvophobic interaction may be more appropriate. Nevertheless, for simplicity of notation, we continue to use the same symbol for these other solvents as well. 

We continue the use of the term hydrophobic interaction even when reference is made to nonaqueous solvents. A more appropriate term for the latter could be solvophobic interaction. ... 

Intermolecular interaction A collective term for the attractive (and repulsive) forces that control the association of two or more molecular entities. Intermolecular interactions include electrostatic (Coulombic) forces, van der Waals forces including dispersion (London) forces, hydrogen bonding interactions, Lewis acid—Lewis base interactions, electron-donor—electron-acceptor interactions, and the hydrophobic (solvophobic) effect. The same types of interactions can also occur between parts of the same molecular entity (intramolecular interactions). Although some interactions are weak relative to a covalent bond, others are not. The term includes a range of bonding characters from predominantly covalent, polar covalent, or ionic. 

Supramolecular aggregate A collection of many molecular entities possessing a degree of order that is exclusively maintained through intermolecular interactions (including hydrophobic or solvophobic interactions). 

Zheng et al. investigated how organic solvents (cyclohexane, p-xylene, toluene, and benzene) worked in the formation of [bmimjBF -based oil-in-IL nonaqueous microemulsion systems [12]. The added molecular solvents provided a nonpolar environment that resulted in the aggregation of the hydrophobic tails of the surfactant TX-lOO, so that the molecular solvents formed droplets dispersed in the continuous [bmim]BF phase. Results of 2D H-NMR confirmed that the solvophobic interaction between the molecular solvents and the hydrophobic tails of TX-lOO was the driving force in the formation of those oil-in-IL microemulsions. 

The hydrophobic interaction also occurs in other solvents. Solvophobic interactions have been exploited in nonaqueous media using surfactants based around silicone oils or fluorocarbons. The expulsion of both of these molecular groups by bulk liquids leads to adsorption at air-solution interfaces and to the formation of stable, nonaqueous foams, that are used in the production of both rigid and flexible isocyanate-based polymeric foams for insulation and cushioning applications [3]. 

To address the difficulty imposed by the limitations on sampling and the time scales accessible to computer simulations of atomic-level models, mimimal models of proteins have been developed. These models are meant to preserve the most fundamental interactions that are believed to contribute to the thermodynamic and kinetic properties of proteins (see Protein Modeling). These include solvophobic interactions (hydrophobic/hydrophilic partitioning), backbone hydrogen bonding, and structural constraints (imposed by backbone dihedral angles summarized in the Ramachandran potential energy surface). ... 

Separations in hydrophobic interaction chromatography have been modeled as a function of the ionic strength of the buffer and of the hydrophobicity of the column, and tested using the elution of lysozyme and ovalbumin from octyl-, butyl- and phenyl-Sepharose phases.2 The theoretical framework used preferential interaction analysis, a theory competitive to solvophobic theory. Solvophobic theory views protein-surface interaction as a two-step process. In this model, the protein appears in a cavity in the water formed above the adsorption site and then adsorbs to the phase, with the free energy change... 

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