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Wimley-White whole-residue hydrophobicity scales. The hydrophobicity scales developed by physical property methods are based on the measurement of different physical properties. Examples include, partial molar heat capacity, transition temperature and surface tension. Physical methods are easy to use and flexible in terms of solute.
Schematic of a liquid drop showing the quantities in the Young equation. The contact angle (symbol θ C) is the angle between a liquid surface and a solid surface where they meet. More specifically, it is the angle between the surface tangent on the liquid–vapor interface and the tangent on the solid–liquid interface at their intersection.
In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. [1] In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents .
One example of a superhydrophobic surface in nature is the Lotus leaf. [12] Lotus leaves have a typical contact angle of θ ∼ 160 ∘ {\displaystyle \theta \sim 160^{\circ }} , ultra low water adhesion due to minimal contact areas, and a self cleaning property which is characterised by the Cassie-Baxter equation. [ 13 ]
In biochemistry, the hydrophobic effect can be used to separate mixtures of proteins based on their hydrophobicity. Column chromatography with a hydrophobic stationary phase such as phenyl-sepharose will cause more hydrophobic proteins to travel more slowly, while less hydrophobic ones elute from the column sooner. To achieve better separation ...
For example, the blood/gas partition coefficient of a general anesthetic measures how easily the anesthetic passes from gas to blood. [5] Partition coefficients can also be defined when one of the phases is solid , for instance, when one phase is a molten metal and the second is a solid metal, [ 6 ] or when both phases are solids. [ 7 ]
There are only empirical equations to relate surface tension and temperature: Eötvös: [21] [22] [23] / = (). Here V is the molar volume of a substance, T C is the critical temperature and k is a constant valid for almost all substances. [21] A typical value is k = 2.1 × 10 −7 J K −1 mol − 2 ⁄ 3.
The Craig plot, named after Paul N. Craig, is a plot of two substituent parameters (e.g. Hansch-Fujita π constant and sigma constant) used in rational drug design. [1] Two most used forms of a Craig plot are plotting the sigma constants of the Hammett equation versus hydrophobicity; plotting the steric terms of the Taft equation against ...