Hydrophobic group

This refers to long-chain alkyl groups, fluorocarbon chains, benzene rings, and alicyclic atomic groups. It is also called an oleophilic group. These atomic groups do not easily form hydrogen bonds with water molecules. In other words, they have poor affinity for water. When hydrogen atoms are attached to these atomic groups to make compounds, they become insoluble or poorly soluble in water without exception. On the other hand, they are compatible with oil-soluble compounds such as kerosene and benzene, and have high solubility. Soap, ABS, and other surfactants have both hydrophilic and hydrophobic groups in their molecules, and therefore gather at the interface between oil and water. This causes a large change in interfacial tension.

[Yamazaki Akira]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

長鎖のアルキル基やフルオロカーボン鎖、あるいはベンゼン環や脂環式の原子団をさす。親油基oleophilic groupともいう。これらの原子団は水分子と水素結合をつくりにくい。つまり水との親和性に乏しい。これらの原子団に水素原子をつけて化合物をつくると、例外なく水に不溶・難溶のものとなる。逆にケロシンやベンゼンなど油溶性の化合物とはよくなじみ、溶解度も大きい。せっけんやABSその他の界面活性剤は、親水基と疎水基の両方を分子内にもっており、したがって油と水との界面に群がる。このために界面張力に大きな変化を引き起こすのである。

［山崎　昶］

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