Solvent/water systems, different

Catalyst Cation. The logarithms of extraction constants for symmetrical tetra- -alkylammonium salts (log rise by ca 0.54 per added C atom. Although absolute numerical values for extraction coefficients are vastly different in various solvents and for various anions, this relation holds as a first approximation for most solvent—water combinations tested and for many anions. It is important to note, however, that the lipophilicity of phenyl and benzyl groups carrying ammonium salts is much lower than the number of C atoms might suggest. Benzyl is extracted between / -propyl and -butyl. The extraction constants of tetra- -butylammonium salts are about 140 times larger than the constants for tetra- -propylammonium salts of the same anion in the same solvent—water system. 

A. Effect of Different Wetting Solvent-Water Systems... 

Different balance between intermolecular forces can be accessible via partition coefficients measured in solvents systems other than the traditional 1-octanol/water. Therefore there was a growing interest in the partition processes in several solvent/ water systems [64, 65] and in particular the critical quartet of solvents which was designed to merge the main information about a solute concerning its partition and transport. Only a few studies have been performed to characterize the lipophilicity profile of new chemical entities in different solvent/water systems and consequently the number of methods attempting to model such partitioning systems is limited. 

Ottaviani, G., Martel, S., Escalara, C., Nicolle, E. and Carrupt, P.A. (2008) The PAMPA technique as a HTS tool for partition coefficients determination in different solvent/water systems. European Journal of Pharmaceutical Sciences,... 

LFERs Relating Partition Constants in Different Solvent-Water Systems Model for Description of Organic Solvent-Water Partitioning Illustrative Example 7.1 Evaluating the Factors that Govern the Organic Solvent-Water Partitioning of a Compound... 

Comparison of Different Organic Solvent-Water Systems 217... 

Such multiparameter LFERs have been developed for a few organic solvent-water systems (Table 7.2.) The magnitudes of the fitted coefficients, when combined with an individual solute s Vix, nDh nit ah /3, values, reveal the importance of each inter-molecular interaction to the overall partitioning process for that chemical. To interpret the various terms, we note that these coefficients reflect the differences of the corresponding terms used to describe the partitioning of the compounds from air to water and from air to organic solvent, respectively (see Chapter 6). Some applications of Eq. 7-9 are discussed in Illustrative Example 7.1. 

Kishino and Kobayashi (1994) determined the n-octane-water (Kioclw) and n-octanol-water (Kiow) partition constants of a series of chlorinated phenols (see Table below). Plot the log Kioctw values versus the log Kiov/ values of the 13 compounds. Inspect the data and derive meaningfull LFERs of the type Eq. 7-7 for subsets of compounds. Discuss your findings in terms of the molecular interactions that govern the partitioning of the chlorinated phenols in the two different solvent-water systems. 

Aw G° and Aq 0° are not experimentally accessible quantities, e.g., the standard ion transfer potential can be measured with respect to the potential difference between the two terminals of an electrochemical cell using two appropriate reference electrodes. The values of these quantities have been compiled for several organic solvent-water systems on the basis of a nonthermodynamic assumption [4, 11]. In general, the values of the Gibbs energy of transfer of an ion in Eq. (2) differ from those for the transfer from one pure solvent to another pure solvent. 

Substituent descriptors defined by measuring the additive contributions of molecular fragments to the hydrogen bonding ability of a molecule [Seiler, 1974]. Such descriptors are calculated from the difference in logP value in two solvent/water systems ... 

The computed values of real (U ) and ideal (Vp) energies of interaction between solvents and a delocalized electron, and also the surface potentials x used in calculating Vp are listed in Table 2. The mercury-solvent Volta potential differences needed in the calculations of U were computed from the Volta potential differences for the solvent-water system these have been measured for methanol, ethanol, dimethylsulfoxide, ethylene glycol, and propylene glycol-1,2 by Damaskin and co-... 

Analogous partition data are available for solvents other than octanol, e.g. olive oil, and these may be more pertinent in certain situations. However, log P values based on octanol/water partition are easily accessible for thousands of substances and, for most of the compounds found in perfumery, may be estimated reasonably well using one of the mathematical prediction models described in the literature [the two most well known are those due to Rekker (1977), and to Leo et al. (1971)]. Additionally, it is often true that for many materials partition coefficients determined in different solvent-water systems often correlate strongly with one another. 

R Organic acids, alcohols, phenols, ketones, esters, ethers, amides, imines, imides, nitriles, aromatic amines, sulfonamides, barbiturates, aromatic hydrocarbons, other miscellaneous groups. Regression equations for calculation of from Kw in any of 20 different solvent/water systems are given. Equations primarily for mono-functional chemical classes. 

While partition coefficients from many different organic solvent/water systems have been used in early structure-activity relationships, n-octanol became the organic solvent of choice after the pioneering work of Hansch on n-octanol/water partition coefficients of substituted phenoxyacetic acids and the lipophilicity parameter 7t derived from these partition coefficients [14, 15, 17, 18, 173, 180]. 

From thermodynamic considerations, the equilibrium partitioning of an organic compound in a solvent/water system is determined by the difference between the partial molar excess free energy (AG% ) of the compound in the organic solvent (o) and in the water phase (w) with molar volumes and V, respectively (Schwarzenbach, Gschwend and Imboden, 1993) ... 

The presumed relationships between partitioning in different solvent/water systems (organic phases A and B) according to the Collander equation (1951)... 

Table 1.2 Partition coefficients obtained in different solvent/water systems (Dunn, Grigoras and Johansson, 1986).

In recent years, the use of solvent-borne adhesives has been seriously restricted. Solvents are, in general, volatile, flammable and toxic. Further, solvent may react with other airborne contaminants contributing to smog formation and workplace exposure. These arguments have limited the use of solvent-bome adhesives by different national and European regulations. Although solvent recovery systems and afterburners can be effectively attached to ventilation equipment, many factories are switching to the use of water-borne rubber adhesives, hot melts or 100% solids reactive systems, often at the expense of product performance or labour efficiency. 

Table 1 Effect of Ratio of Different Solvents in Water System on Polymer Loading and Grafting Yield...

Solvation and especially hydration are rather complex phenomena and little is known about them. Depending on the kind of molecular groups, atoms or ions interacting with the solvent, one can differ between lyo- or hydrophilic and lyo-or hydrophobic solvation or hydration. Due to these interactions the so-called liquid structure is changed. Therefore it seems to be unavoidable to consider, at least very briefly, the intermolecular interactions and the main features of liquids, especially water structure before dealing with solvation/hydration and their effects on the formation of ordered structures in the colloidal systems mentioned above. 

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