Solvophobic parameters

Ri seems to be related to solute size, but it is obtained by an iterative curve-fitting procedure. The parameters M and D are characteristic of the solvent. For water Af = 0. A solvophobicity parameter Sp is then defined for the solvent having value M... 

There are numerous attempts to correlate solvent parameters with the reaction rate of Diels-Alder reactions122. Examples are the Brownstein Polarity Parameter S123, the Solvophobicity Parameter Sp124,125 the D-it parameter (based on the solvent effect on the reaction of tetracyanoethylene and diazodiphenylmethane with benzene as the reference solvent)126 or the Acceptor Number / /V127, l2X (a parameter which describes the ability of a solvent to act as an electron pair acceptor)129. These examples included either reactions that were next to insensitive to solvent effects (like that in Table 9) or reactions in which the reactants mainly interact with the electron pair on the donor atom of the solvent130. 

Solvent coordination number, 134, 403 Solvent effects, 385, 418 initial and transition state, 418 kinetic measures of, 427 Solvent ionizing power parameter, 430 Solvent isotope effects, 272, 300 Solvent nucleophilicity, 431 Solvent participation, covalent, 429 Solvent polarity, 399, 425 Solvent polarity parameter, 436 Solvent properties, 389 Solvent-separated complex, 152 Solvent sorting, 404 Solvent structure, 402 Solvophobic interaction, 395 Solvophobicity parameter, 427 Sound absorption chemical, 145 classical, 145... 

GRUNWALD-WlNSTEIN EQUATION KAMLET-TAFT SOLVENT PARAMETERS KOPPEL-PALM SOLVENT PARAMETERS SOLVOPHOBICITY PARAMETER Z-VALUE. 

There are numerous attempts to correlate solvent parameters with the reaction rate of Diels-Alder reactions. Examples are the Brownstein Polarity Parameter 5, the Solvophobicity Parameter the D-n parameter (based on the solvent effect on... 

The drop in enantioselectivity going from the organic system to the aqueous phase was attributed to solvent effects and the difference in enantioselectivity is due to the reaction kinetics in the two solvents [16]. When the reaction was carried out in alcohol/water solvent mixtures, an increase in water content induced a decrease in enantioselectivity. In a systematic study of the influence of various solvents on the enantioselectivity in the reduction of dehydroamino acids, a linear relationship was found between log (%S/%R) and the solvophobicity parameter Sp of various solvents, log (% S/% R) decreasing with increasing Sp. 

Breslow also noted that the presence of detergents such as sodium dodecyl-sulfate and cetyltrimethylammonium bromide (data not shown) had little effect on the product ratios of these aqueous Diels-Alder reactions. These results suggest that the increased endo/exo ratios and rates measured for a series of similar Diels-Alder reactions in aqueous detergent solutions by Sauer and co-workers may not be due to micellar effects as proposed [41]. Further support for Breslow s hydrophobic solvent effect hypothesis came from a study of Diels-Alder reactions of cyclopentadiene and a series of maleate and fumarate derivatives by Schneider and Sangwan [42]. They found a better correlation between the endo/exo product ratios for these reactions and solvophobicity parameters for various solvent systems as opposed to polarity effects alone. Subsequently, Cativiela et al. noted that a dual model (solvophobicity and polarity effects) can satisfactorily account... 

The solvophobic model of Hquid-phase nonideaHty takes into account solute—solvent interactions on the molecular level. In this view, all dissolved molecules expose microsurface area to the surrounding solvent and are acted on by the so-called solvophobic forces (41). These forces, which involve both enthalpy and entropy effects, are described generally by a branch of solution thermodynamics known as solvophobic theory. This general solution interaction approach takes into account the effect of the solvent on partitioning by considering two hypothetical steps. Eirst, cavities in the solvent must be created to contain the partitioned species. Second, the partitioned species is placed in the cavities, where interactions can occur with the surrounding solvent. The idea of solvophobic forces has been used to estimate such diverse physical properties as absorbabiHty, Henry s constant, and aqueous solubiHty (41—44). A principal drawback is calculational complexity and difficulty of finding values for the model input parameters. 

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%... 

In section 8.2 we described the solvophobic effect, which theory leads us to expect is related to the solvent surface tension. Abraham et al. have developed a di erent measure of solvophobicity by relating the transfer free energy 8MGtr(S<—W) for several solutes from water to given solvent S (which may be an aqueous-organic mixture) to an empirical solute parameter R by... 

In spite of widespread applications, the exact mechanism of retention in reversed-phase chromatography is still controversial. Various theoretical models of retention for RPC were suggested, such as the model using the Hildebrand solubility parameter theory [32,51-53], or the model supported by the concept of molecular connectivity [54], models based on the solvophobic theory [55,56) or on the molecular statistical theory [57j. Unfortunately, sophisticated models introduce a number of physicochemical constants, which are often not known or are difficult and time-consuming to determine, so that such models are not very suitable for rapid prediction of retention data. 

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