hydrophobic
London interactions c. London dispersion forces Hydrophilic and Hydrophobic Solutes A solute can be classified as hydrophilic literally, water loving , meaning that it has an electrostatic attraction to water, or hydrophobic water fearing , meaning that it repels water. A hydrophilic substance is polar and often contains OH or NH groups that can form hydrogen bonds to water. For example, glucose with its five OH groups is hydrophilic. In contrast, a hydrophobic substance may be polar but usually contains CH bonds that do not interact favorably with water, as is the case with naphthalene and n-octane. Hydrophilic substances tend to be very soluble in water and other strongly polar solvents, whereas hydrophobic substances are essentially insoluble in water and soluble in nonpolar solvents such as benzene and cyclohexane. The difference between hydrophilic and hydrophobic substances has substantial consequences in biological systems. For example, vitamins can be classified as eitherfat soluble or water soluble. Fatsoluble vitamins, such as vitamin A, are mostly nonpolar, hydrophobic molecules. As a result, they tend to be absorbed into fatty tissues and stored there. In contrast, water-soluble vitamins, such as vitamin C, are polar, hydrophilic molecules that circulate in the blood and intracellular fluids, which are primarily aqueous. Water-soluble vitamins are therefore excreted much more rapidly from the body and must be replenished in our daily diet. A comparison of the chemical structures of vitamin A and vitamin C quickly reveals why one is hydrophobic and the other hydrophilic.