Hydrological cycle

Hydrogen Bonding

Hydrogen bonding is a special type of dipole-dipole interaction that occurs between an electron deficient hydrogen atom on one molecule and an electron rich atom on another molecule. It is a type of intermolecular force that is responsible for many of the properties of water, proteins, DNA, and many other substances.

Overview

Hydrogen bonds are formed when a hydrogen atom bonded to a highly electronegative atom such as oxygen, nitrogen, or fluorine experiences attraction to some other nearby highly electronegative atom. They can occur between molecules (intermolecular) or within different parts of a single molecule (intramolecular). The hydrogen bond is one of the strongest intermolecular attractions, but weaker than covalent or ionic bonds.

Properties

Hydrogen bonds have certain properties that set them apart from other types of bonds. They are directional, meaning they have a preferred spatial arrangement, and they are strong, typically 5 to 30 kilojoules per mole, which is stronger than a van der Waals interaction, but weaker than covalent or ionic bonds.

Role in Biological Systems

Hydrogen bonding plays a key role in the structure and function of biological systems. For example, the double helix structure of DNA is due to hydrogen bonding between the base pairs. In proteins, hydrogen bonds are essential for maintaining the secondary and tertiary structure.

Role in Physical Properties

Hydrogen bonding also affects the physical properties of substances. For example, the high boiling point of water compared to other similar sized molecules is due to hydrogen bonding. It also contributes to the unique properties of ice and snow.

See Also

• Covalent bond
• Ionic bond
• Van der Waals forces
• Dipole-dipole interaction