Nonpolar molecule 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. 

The given structure shows two molecules of TTA to have reacted with a cobalt ion to form the cobalt-TTA complex, in which the cobalt atom forms a valence bond solid lines) with one, and a coordinate bond (broken lines) with the other, oxygen atom of each TTA molecule. Thus, in the cobalt-TTA complex there is a six-membered ring formed by each TTA molecule with the cobalt atom. Metal chelate complexes of this type have good stability, they are nonpolar and soluble in the organic phase. The usefulness of the chelating extractants in solvent extraction is therefore obvious. 

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. 

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. 

Given the interest in extended carbon systems in recent years, it seemed useful to study the solubility of C60 (fullerene) in various organic liquids.54 55 It was now for the solvents that the molecular surface properties were computed. The resulting Eq. (14) shows that, for this large nonpolar solute, solubility is enhanced by solvent molecule surface area and by the latter having somewhat... 

Drug molecules are transported across cell membranes. Because of the lipid bilayer construction of the membrane (Appendix 2), nonpolar (lipid-soluble) molecules are able to diffuse and penetrate the cell membrane. Polar molecules, however, cannot penetrate the cell membrane readily via passive diffusion and rely on other transport mechanisms. 

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. 

Polarity is a physical property of a compound, which relates other physical properties, e.g. melting and boiling points, solubility and intermolecular interactions between molecules. Generally, there is a direct correlation between the polarity of a molecule and the number and types of polar or nonpolar covalent bond that are present. In a few cases, a molecule having polar bonds, but in a symmetrical arrangement, may give rise to a nonpolar molecule, e.g. carbon dioxide (CO2). 

The solubility of molecules can be explained on the basis of the polarity of molecules. Polar, e.g. water, and nonpolar, e.g. benzene, solvents do not mix. In general, like dissolves like i.e., materials with similar polarity are soluble in each other. A polar solvent, e.g. water, has partial charges that can interact with the partial charges on a polar compound, e.g. sodium chloride (NaCl). As nonpolar compounds have no net charge, polar solvents are not attracted to them. Alkanes are nonpolar molecules, and are insoluble in polar solvent, e.g. water, and soluble in nonpolar solvent, e.g. petroleum ether. The hydrogen bonding and other nonbonding interactions between molecules are described in Chapter 2. 

Nonpolar molecules tend to have low solubilities in water, and large nonpolar solutes tend to form aggregates in aqueous solution. In the past these tendencies were sometimes explained by invoking a special hydrophobic bond between nonpolar groups. However, bond is a misnomer here, and it is better to refer to an effect, because there is no exchange of bonding electrons involved in either of the tendencies noted above. Instead, the hydrophobic effect is a combination of several of the fundamental noncovalent interactions, and it involves details of the organization of water molecules around nonpolar solute molecules. 

Hydrogen bonds between water molecules provide the cohesive forces that make water a liquid at room temperature and that favor the extreme ordering of molecules that is typical of crystalline water (ice). Polar biomolecules dissolve readily in water because they can replace water-water interactions with more energetically favorable water-solute interactions. In contrast, nonpolar biomolecules interfere with water-water interactions but are unable to form water-solute interactions— consequently, nonpolar molecules are poorly soluble in water. In aqueous solutions, nonpolar molecules tend to cluster together. 

Polar molecules are easier to excrete because of their greater solubility in water. For example, upon dissolving in water, they can be excreted through urine. Nonpolar molecules, by contrast, tend to adhere within nonpolar tissues, such as fat tissues. Vitamin A, for example, is a nonpolar molecule that is retained by the body within fat tissues for many months. This is in contrast to polar B-vitamins, which pass out of the body through the urine within a day. 

Chlorophyll is a nonpolar molecule so it is soluble in most organic solvents. Acetone disrupts protein-pigment complexes (see Experiment 8). A more efficient extraction could be achieved if several extractions were carried out and the extracts pooled. 

Pentane is a nonpolar molecule and is unlikely to have strong intermolecular interactions with polar water molecules. 1-Butanol, however, has an -OH group just as water does, and is therefore a polar molecule that can form hydrogen bonds with water. 1-Butanol is more soluble in water. 

As expected for a molecular solid that contains small, nonpolar molecules, white phosphorus has a low melting point (44°C) and is soluble in nonpolar solvents such as carbon disulfide, CS2. It is highly reactive, bursting into flames when exposed to air, and is thus stored underwater. When white phosphorus is heated in the absence of air at about 300°C, it is converted to the more stable red form. Consistent with its polymeric structure, red phosphorus is higher melting (mp 600°C), less soluble, and less reactive than white phosphorus, and it does not ignite on contact with air (Figure 19.9). 

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