Hydrogen Bond

A hydrogen bond is the electromagnetic attractive interaction of a hydrogen atom and an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. It is not a true chemical bond. The hydrogen atom has an attraction to another electronegative atom. These attractions can occur between molecules (intermolecularly), or within different parts of a single molecule (intramolecularly). The hydrogen bond (5 to 30 kJ/mole) is stronger than a van der Waals interaction, but weaker than covalent or ionic bonds. This type of bond occurs in both inorganic molecules such as water and organic molecules like DNA and proteins.

Intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C) compared to the other group 16 hydrides that have no hydrogen bonds. Intramolecular hydrogen bonding is partly responsible for the secondary, tertiary, and quaternary structures of proteins and nucleic acids. It also plays an important role in the structure of polymers, both synthetic and natural.

In 2011 an IUPAC Task Group recommended a modern evidence based definition of hydrogen bonding. This new definition was published in the IUPAC journal Pure and Applied Chemistry, this detailed technical report provides the rationale behind the new definition.