hydrogen bond otherwise H-bond (rus. водородная связь) — attraction between a covalently bound hydrogen atom to covalently bound electronegative atom (O, N, F, Cl).

Description

A hydrogen bond requires two polar covalent bonds, of which one involves a hydrogen atom bearing an effective positive charge, and another – an electronegative atom (oxygen, nitrogen, halogen) with an effective negative charge. Normally, the hydrogen bonds play a crucial role in the intermolecular interaction, although there are numerous examples of intramolecular hydrogen bonds (e.g. in proteins). The hydrogen bond is a key interaction in supramolecular chemistry. It defines the structure of proteins, DNA double helix (see Fig. 1), water and ice, supramolecular assemblies and polymers, and influences the properties of many solutions.

The energy of hydrogen bonds varies widely, from 5 to 100 kJ/mole, but generally hydrogen bonds are much weaker than covalent bonds (see Fig. 2). Depending on the energy, a hydrogen bond can differ in character, from purely electrostatic (weak bond) to predominantly covalent (strong bond).

Illustrations

Fig. 1.Hydrogen bonds between nitrogen bases defining DNA structure.
Fig. 1.Hydrogen bonds between nitrogen bases defining DNA structure.
Fig. 2. Comparison of hydrogen bond and covalent bond energy (kJ/mol).
Fig. 2. Comparison of hydrogen bond and covalent bond energy (kJ/mol).

Author

  • Eremin Vadim V.

Source

  1. Steed JW, Atwood JL. Supramolecular Chemistry — Chichester: John Wiley & Sons Ltd, 2000.

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