Liquid solubilizers dielectric constant

Liquid solubilizers act by reducing the dielectric constant properties of the solvent system, thereby reducing the electrical conductance capabilities of the solvent and increasing the solubility of hydrophobic or non-polar drugs. Lanoxin, Valium, and Nembutal are examples of commercially available sterile solutions containing cosolvent solubilizers. A popular combination consists of 40% propylene glycol and 10 /o ethanol in water. 

The last point which can be evoked here is conceptually linked to the hot-spot theory. If the limit liquid layers around a bubble are in direct contact with the heated and pressurized bubble content, far above the critical point of the liquid, these layers should be in a supercritical state. 23 This attractive hypothesis (see p. 61) was used by Hoffmann et al to rationalize the sonolysis of nitrophenyl derivatives. Supercritical fluids are characterized by a very high flexibility of important parameters (density, dielectric constant, solubilizing power) as a function of pressure. Experts in the field distinguish gas-like and liquid-like media, in which the kinetics of a reaction can vary over a broad range. For instance, the conjugate addition of piperidine to methyl propiolate was studied in supercritical ethane or fluoroform (Fig. 5). ... 

The other hydrogen halides, with lower boiling points, shorter liquid ranges, and negligible self-dissociation, are less useful as solvents. Considerably lower dielectric constants, as compared to HF, also mean that these compounds do not, in general, solubilize ionic compounds very readily. Nevertheless, work with HCl has indicated that this solvent system provides a convenient medium for the preparation of a number of chlorinated or protonated inorganic and organic products. 

Due to their ability to form complexes selectively with metal cations and thereby solubilize such cations in liquid media of low dielectric constant, macrocyclic multidentate ligands have been widely investigated as carriers in metal ion transport processes for the past two decades (2-P). Such macrocycles include crown ethers, lariat ethers (crown ethers with a side arm which contains potential binding sites) (JO), calixarenes, and some cryptands. Studies of structural variations within a given... 

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