Solubilization association constant

The extent of solubilization of the substrate to the micelle can be related with the association constant or the binding constant. Some of the important models developed to explain the micellar effect are described briefly as follows ... 

Another type of biphase partition comprises equilibration of a crown ether-containing solution with a sparingly soluble solid salt. Assuming that the amount of free salt [M+.X in (1)] at equilibrium equals the solubility—which can be determined separately—one can calculate the association constant ATlp from the amount of solubilized salt. Reinhoudt et al. (1977) applied this technique using Zeise s salts. 

Association constant (M-1) for the binding of water by crown ethers to form a 1 1 complex. Estimated accuracy 10% c Molar ratio solubilized water/crown ether... 

The determination of the association constant K values can be done either graphically or numerically (Kertes and Gutmann, 1976). The K values can be used to estimate thermodynamic quantities such as AG°, AH° and AS0. The interactions of polar substances, such as methanol, ethanol and acetone, with Aerosol OT in toluene systems were examined (Kon-no, 1993). The negative AG° value was found in the decreased order methanol > ethanol > acetone and the contribution to AG° was AH° > TAS°. This result indicates that the solubilization of three solutes with Aerosol OT micelle is an enthalpy driven process. 

The total solubilizate concentration is a function of the stepwise association constant, K, between a solubilizate and a monomer concentration solubilizate. It is very useful to consider the factors influencing solubilization. These values determine the general behavior of solubilization as follows ... 

A primary indication on how well the monomers have been chosen is to simply see whether they are capable of assisting solubilization of the template in the prepolymerization mixture. A small-scale solubility test may thus be a good way to initially screen the monomers for strong monomer-template interactions. Weak interactions may be revealed by complexation induced spectral changes (in NMR,UVor fluorescence spectra). The complexation induced shifts of the characteristic H-NMR signals of the template upon increasing monomer concentrations are often used to estimate the monomer-template association constants. Prior to this, however, knowledge about the stoichiometry of the monomer-template complexation and the tendency of the monomer and template to self-associate are required.The former can be obtained by means of a so-called Job s plot whereas the latter by a dilution experiment. 

Water-soluble pillar[6]arenes can be prepared using the same method as the synthesis of water-soluble pillar[5]arenes. The introduction of water-soluble substituents, such as cationic, anionic and nonionic moieties, allows pillar[6]arenes to solubilize in aqueous media. The first water-soluble pillar[6]arene was synthesized by Huang and co-workers, by introducing 12 carbojylate moieties (Figure 5.31, H5.36). H5.36 could capture paraquat (Table 5.9, run 145, G5.117) in water with a high association constant [ T= (1.02 0.10) x 10 M ], which is much higher than that of the anionic water-soluble pillar[5]arene H5.11 [Table 5.4, run 63, K= (8.20 1.70)xl0 M... 

If the concentration of solubilizates incorporates into micelles is close to or higher than the micellar concentration, we have to think about the distribution of solubilizates among micelles. As with solubilization, the distribution of solubilizates among micelles can be handled successfully only by rearding micelles as chemical species. The equations in Section 9.3 clearly indicate that the association constants between micelles and solubilizates determine the distribution of solubilizates among micelles. The stepwise association constants Kj and the concentration of MR, are given... 

We now address the effects of a polydisperse micellar aggregation number of the thermodynamic expressions of solubilization. One strong effect is variation of the association constant Kj, We define a new association constant which is Kj of the micelles of aggregation number n. Suppose the polydispersity of the aggregation number of micelles ranges from a to p. The concentration of micelles of aggregation number n with no solubilizate association becomes... 

As mentioned, the Poisson distribution shows excellent agreement with reality as long as the extent of solubilization is small. It should be stressed, however, that the distribution of solubilizates among micelles is determined by their association constants with micelles, not by mathematics. At solubilities to which the Poisson distribution is not applicable, the situation should be discussed from the viewpoint of microemulsion. 

Surfactants having an appropriate hydrophobic/hydrophilic balance (sodium bis(-2-ethylhexyl)sufosuccinate, or AOT, for example) undergo concentration-dependent self association in apolar solvents to form reversed or inverted micelles (Fig. 33) [256-262]. Reversed micelles are capable of solubilizing a large number of water molecules (AOT reversed micelles in hexane are able to take up 60 water molecules per surfactant molecule, for example). Reversed-micelle-entrapped water pools are unique they differ significantly from bulk water. At relatively small water-to-surfactant ratios (w = 8-10, where w = [H20]/[Surfactant]), all of the water molecules are strongly bound to the surfactant headgroups. Substrate solubilization in the restricted water pools of reversed micelles results in altered dissociation constants [256, 257, 263-265], reactivities [256, 258, 266], and reaction products [267]. 

While in the air compartment, the contaminant solubilizes in the vapor-liquid phase or is associated with aerosol particles by adsorption. It is also prone to desorption from the aerosol particles into the vapor phase. Relevant properties of the air used to model transport of partitioning of a contaminant in the air compartment include temperature, turbulence, wind speed, size and composition of aerosol particles, etc.16,19 Relevant properties of the contaminant that measure its tendency to partition among the vapor, liquid, and solid phases in the air include its aqueous solubility (Saq), vapor pressure (VP), Henry s constant... 

Acetonitrile (ACN) possesses some unique properties, such as a high dielectric constant (35.95) and the solubilization of many inorganic and organic materials . It is actually one of the few simple aprotic solvents miscible in water at any ratio. X-ray diffraction studies of pure acetonitrile revealed that ACN molecules do not strongly interact with themselves and are only weakly associated via dipole-dipole interaction . The IR spectrum of pure acetonitrile includes two major bands placed at 2257 and 2295 cm . The former, called V2, originates from the C=N stretching mode while the latter is a combination band composed of the CCH bend V3 and C—C stretch V4 modes. ... 

---