Hydrogen bond

Hydrogen Bond

A Hydrogen bond (pronounced: /ˈhaɪdrədʒən bɒnd/) is a type of attractive intermolecular force that exists between two partial electric charges of opposite polarity. Although weaker than covalent bonds and ionic bonds, hydrogen bonds are responsible for many of the anomalous physical and chemical properties of compounds.

Etymology

The term "Hydrogen bond" was first used by the German chemist Hermann Emil Fischer in 1894. It is derived from the Greek words 'hydro' meaning water, and 'gen' meaning to produce or generate. This is because hydrogen bonds are often observed in molecules of water.

Definition

A hydrogen bond is formed when a charged part of a molecule having polar covalent bonds forms an electrostatic interaction with a substance of opposite charge. Molecules that have non-bonding electrons (lone pairs) such as water molecules can form hydrogen bonds.

Properties

Hydrogen bonds have a typical length of 1.97 Ångström (Å) and a strength of 5 to 30 kJ/mol. They are generally stronger than a Van der Waals interaction, but weaker than covalent or ionic bonds. This type of bond can occur between atoms in different molecules or in parts of the same molecule.

Examples

Hydrogen bonds can exist between atoms in different molecules, such as in liquid water where the hydrogen bonds hold the substance together. They also play a key role in the three-dimensional structure that proteins and nucleic acids form in water.

Related Terms

• Covalent bond
• Ionic bond
• Van der Waals forces
• Intermolecular forces
• Polar covalent bond

External links

• Medical encyclopedia article on Hydrogen bond
• Wikipedia's article - Hydrogen bond

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