Molecular geometric factor

It is of particular interest to be able to correlate solubility and partitioning with the molecular stmcture of the surfactant and solute. Likes dissolve like is a well-wom plirase that appears applicable, as we see in microemulsion fonnation where reverse micelles solubilize water and nonnal micelles solubilize hydrocarbons. Surfactant interactions, geometrical factors and solute loading produce limitations, however. There appear to be no universal models for solubilization that are readily available and that rest on molecular stmcture. Correlations of homologous solutes in various micellar solutions have been reviewed by Nagarajan [52]. Some examples of solubilization, such as for polycyclic aromatics in dodecyl sulphonate micelles, are driven by hydrophobic... 

In order to do this, we anticipate the form of the expression for Equation (10.31) will show that 1 /1q can be written as the product of two terms an optical-molecular factor we symbolize as and a geometrical factor 1 + cos where r is the distance from the scattering molecule and 0 is... 

The tortuosity for pore-filling liquids is ideally a purely geometric factor but can, in principle, depend on the fluid-surface interaction and the molecular size if very small pores are present such as in zeolites (see Chapter 3.1). To obtain a measure for a realistic situation, we have used n-heptane as a typical liquid and have computed x... 

On the other hand, the crystal structures of ionic compounds with small molecular ions depend mainly on how space can be filled most efficiently by the ions, following the principle of cations around anions and anions around cations. Geometric factors such as the relative size of the ions and the shape of molecular ions are of prime importance. More details are given in Chapter 7. 

Both Knudsen and molecular diffusion can be described adequately for homogeneous media. However, a porous mass of solid usually contains pores of non-uniform cross-section which pursue a very tortuous path through the particle and which may intersect with many other pores. Thus the flux predicted by an equation for normal bulk diffusion (or for Knudsen diffusion) should be multiplied by a geometric factor which takes into account the tortuosity and the fact that the flow will be impeded by that fraction of the total pellet volume which is solid. It is therefore expedient to define an effective diffusivity De in such a way that the flux of material may be thought of as flowing through an equivalent homogeneous medium. We may then write ... 

To calculate the effective diffusivity in the region of molecular flow, the estimated value of D must be multiplied by the geometric factor e/x which is descriptive of the heterogeneous nature of the porous medium through which diffusion occurs. 

Equations (27)—(29) imply that pseudo-contact shifts Sfc are maximum for complexes displaying large molecular magnetic anisotropies and that structural and geometrical informations can be extracted from the so-called non-linear geometrical factors G (eq. (30)) and Hi (eq. (31)) (Forsberg, 1996 Peters et al., 1996)... 

Ab initio quantum-chemical calculations were used in this study for the interpretation of the experimental data (EPR, IR, and optical). The main purpose of the calculations was to elucidate the question of how the geometric factors (spatial structure of the defect) and chemical ones (nature of the substituents) influence the spectral properties of the defects. At present time such calculations can be carried out on acceptable level for systems comparatively small in size. This makes it necessary to use molecular models for calculations of defects in solids. 

A steric exclusion mechanism implies that a geometric factor and not an energetic one, such as the differences in the intermolecular interactions between the constituents of the water+protein+PEG mixtures is responsible for the local composition around a protein molecule. This constitutes the main difference between the preferential binding in water+protein + PEG mixtures and water+protein+low molecular weight cosolvents (such as urea, glycerol, alcohol, etc.) mixtures. 

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