Nonpolar molecules water solubility

The dissolution of polar molecules in water is favored by dipole—dipole interactions. The solvation of the polar molecules stabilizes them in solution. Nonpolar molecules are soluble in water only with difficulty because the relatively high energy cost associated with dismpting and reforming the hydrogen-bonded water is unfavorable to the former occurring. 

As shown in Figure 1.2, the solvent strength of supercritical carbon dioxide approaches that of hydrocarbons or halocarbons. As a solvent, C02 is often compared to fluorinated solvents. In general, most nonpolar molecules are soluble in C02, while most polar compounds and polymers are insoluble (Hyatt, 1984). High vapor pressure fluids (e.g., acetone, methanol, ethers), many vinyl monomers (e.g., acrylates, styrenics, and olefins), free-radical initiators (e.g., azo- and peroxy-based initiators), and fluorocarbons are soluble in liquid and supercritical C02. Water and highly ionic compounds, however, are fairly insoluble in C02 (King et al., 1992 Lowry and Erickson, 1927). Only two classes of polymers, siloxane-based polymers and amorphous fluoropolymers, are soluble in C02 at relatively mild conditions (T < 100 °C and P < 350 bar) (DeSimone et al., 1992, 1994 McHugh and Krukonis, 1994). 

Water solubility is determined by polarity. Polar molecules are soluble in water, while nonpolar molecules are soluble in organic solvents. 

The solubility (or insolubility) of different vitamins is of concern in nutrition. Molecules of vitamins B and C contain several —OH groups that can form hydrogen bonds with water (Figure 10.3). As a result, they are water-soluble, readily excreted by the body, and must be consumed daily. In contrast, vitamins A, D, E, and K, whose molecules are relatively nonpolar, are water-insoluble. These vitamins are not so readily excreted they tend to stay behind in fatty tissues. This means that the body can draw on its reservoir of vitamins A, D, E, and K to deal with sporadic deficiencies. Conversely, megadoses of these vitamins can lead to very high, possibly toxic, concentrations in the body. 

Bilirubin is nonpolar and would persist in cells (eg, bound to lipids) if not rendered water-soluble. Hepatocytes convert bilirubin to a polar form, which is readily excreted in the bile, by adding glucuronic acid molecules to it. This process is called conjugation and can employ polar molecules other than glucuronic acid (eg, sulfate). Many steroid hormones and drugs are also... 

Traditional electrophoresis and capillary electrophoresis are competitive techniques as both can be used for the analysis of similar types of samples. On the other hand, whereas HPLC and GC are complementary techniques since they are generally applicable to different sample types, HPLC and CE are more competitive with each other since they are applicable to many of the same types of samples. Yet, they exhibit different selec-tivities and thus are very suitable for cross-validation studies. CE is well suited for analysis of both polar and nonpolar compounds, i.e. water-soluble and water-insoluble compounds. CE may separate compounds that have been traditionally difficult to handle by HPLC (e.g. polar substances, large molecules, limited size samples). 

Polar compounds and compounds that ionize can dissolve readily in water. These compounds are said to be hydrophilic. In contrast to hydrophilic substances, hydrocarbons and other nonpolar substances have very low solubility in water because it is energetically more favorable for water molecules to interact with other water molecules rather than with nonpolar molecules. As a result, water molecules tend to exclude nonpolar substances, forcing them to associate with themselves in forming drops, thereby minimizing the contact area between... 

The lipid bilayer arrangement of the plasma membrane renders it selectively permeable. Uncharged or nonpolar molecules, such as oxygen, carbon dioxide, and fatty acids, are lipid soluble and may permeate through the membrane quite readily. Charged or polar molecules, such as glucose, proteins, and ions, are water soluble and impermeable, unable to cross the membrane unassisted. These substances require protein channels or carrier molecules to enter or leave the cell. 

A surfactant is a molecule that is characterized as amphiphilic, i.e., containing both a discrete hydrophilic (water-soluble) or polar portion and a well-defined hydrophobic (oil-soluble) or nonpolar fragment. The hydrophilic portion of the molecule is called the surfactant headgroup the hydrophobic portion of a surfac-... 

Butyl alcohol should be moderately soluble in both water and benzene. A solute that is moderately soluble in both solvents will have some properties in common with each solvent. Both naphthalene and hexane are nonpolar molecules, like benzene, but have no properties in common with water molecules they are soluble in benzene but not in water Sodium chloride consists of charged ions, similar to the charges in the polar bonds of water. Thus, as expected NaCl is very soluble in water. Butyl alcohol, on the other hand, possesses both a nonpolar part (C4H9—) like benzene, and a polar bond (—O —H) like water. In fact, water and butyl alcohol can mutually hydrogen bond. 

The presence of water-soluble macromolecules in solution at submicel-lar concentrations has been reported to enhance the water solubility of hydro-phobic organic chemicals in several instances [19, 106, 113]. The presence of macromolecules in solution can enhance the apparent solubility of solutes by sorptive interactions in the solution phase. The processes by which macromolecules enhance the solubility of pollutants are probably variable as a function of the particular physical and chemical properties of the system. A macromolecule possessing a substantial nonpolar region can sorb a hydrophobic molecule, thereby minimizing the interfacial tension between the solute and the water. 

The polarity of a molecule determines its solubility. Polar molecules attract each other, so polar molecules usually dissolve in polar solvents, such as water. Non-polar molecules do not attract polar molecules enough to compete against the strong attraction between polar molecules. Therefore, nonpolar molecules are not usually soluble in water. Instead, they dissolve in non-polar solvents, such as benzene. 

Soap works because the nonpolar end dissolves in dirt (oil), leaving the polar end outside the dirt. This combination is known as a micelle (see Figure 16-30). To the surrounding water molecules, the micelle appears as a very large ion. These ions tire water-soluble and repel each other due to their like charges, a behavior that causes them to remain separated. Metal ions in hcird water (Ca VMg VFe ) cause a precipitate to form because they react with carboxylate ions to form an insoluble material (also known as the soap scum hanging around the bathtub or shower). 

All surfactants have a common molecular similarity. A portion of the molecule has a long nonpolar chain, frequently a hydrocarbon chain, that promotes oil solubility but water insolubility (the hydrophobic portion— water hating). Another part of the molecule promotes oil insoluble and water soluble properties (the hydrophilic portion—water loving). 

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