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Polar molecules must contain one or more polar bonds due to a difference in electronegativity between the bonded atoms. Molecules containing polar bonds have no molecular polarity if the bond dipoles cancel each other out by symmetry. Polar molecules interact through dipole-dipole intermolecular forces and hydrogen bonds.
Under transmission electron microscopy (TEM), after staining with polar headgroup reactive chemical osmium tetroxide, lamellar lipid phase appears as two thin parallel dark staining lines/sheets, constituted by aligned polar headgroups of lipids. 'Sandwiched' between these two parallel lines, there exists one thicker line/sheet of non-staining ...
An example of these amphiphilic molecules is the lipids that comprise the cell membrane. Another example is soap, which has a hydrophilic head and a hydrophobic tail, allowing it to dissolve in both water and oil. Hydrophilic and hydrophobic molecules are also known as polar molecules and nonpolar molecules, respectively. Some hydrophilic ...
[1] [2] The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. [3]
In reversed phase chromatography, the most polar compounds elute first with the more nonpolar compounds eluting later. The mobile phase is generally a mixture of water and miscible polarity-modifying organic solvent, such as methanol, acetonitrile or THF. Retention increases as the fraction of the polar solvent (water) in the mobile phase is ...
Likewise, larger molecules are generally more polarizable than smaller ones. Water is a very polar molecule, but alkanes and other hydrophobic molecules are more polarizable. Water with its permanent dipole is less likely to change shape due to an external electric field. Alkanes are the most polarizable molecules. [9]
Solvophobic theory attempts to explain interactions between polar solvents and non-polar solutes. In the pure solvent, there are relatively strong cohesive forces between the solvent molecules due to hydrogen bonding or other polar interactions. Hence, non-polar solutes tend not to be soluble in polar solvents because these solvent-solvent ...
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