Hydrophobe

A hydrophobe is a molecule or a portion of a molecule that tends to repel water or has very limited solubility in water. The term emphasizes the water-repelling character of nonpolar or low-polarity surfaces that do not form favorable hydrogen bonds with water molecules.

Hydrophobicity arises because water molecules prefer to interact with each other rather than with nonpolar partners. In aqueous environments, nonpolar groups tend to minimize contact with water, and hydrophobic regions often aggregate or cluster together. This hydrophobic effect is a key driver in many biological and chemical processes, including protein folding, the formation of lipid membranes, and the assembly of micelles by amphiphilic molecules.

Examples of hydrophobic substances include hydrocarbons such as octane and hexane, oils, and many nonpolar organic solvents. It is common in practice to distinguish hydrophobic from lipophilic properties; while many hydrophobic substances are also lipophilic, lipophilicity specifically refers to affinity for fats and lipids, whereas hydrophobicity focuses on water interaction.

In measurement and analysis, hydrophobic character can be assessed by properties such as the partition coefficient (log P) between octanol and water or by water contact angles on surfaces. Understanding hydrophobicity is important in fields ranging from chemistry and materials science to biochemistry and pharmacology.