Hydrogen Bonding

Definition

Hydrogen bonding is a special type of dipole-dipole attraction that occurs between a hydrogen atom covalently bonded to a highly electronegative atom, such as nitrogen, oxygen, or fluorine, and another nearby highly electronegative atom. This intermolecular force is responsible for many of the unique properties of water and other hydrogen-containing compounds.

5 Must Know Facts For Your Next Test

1. Hydrogen bonding is a particularly strong type of dipole-dipole interaction, about 10 times stronger than a typical dipole-dipole force.
2. Hydrogen bonding is responsible for the high boiling point of water compared to other similar molecules, as well as water's high surface tension and ability to undergo capillary action.
3. Hydrogen bonding allows water molecules to form a tetrahedral network of intermolecular attractions, giving water many of its unique physical and chemical properties.
4. Hydrogen bonding is essential for the structure and function of many biological macromolecules, such as DNA and proteins.
5. The strength of hydrogen bonds depends on the electronegativity difference between the hydrogen and the bonded atom, as well as the geometry of the molecules involved.

Review Questions

• Explain how hydrogen bonding contributes to the cohesive properties of liquids, such as surface tension and capillary action.
  • Hydrogen bonding creates strong intermolecular attractions between water molecules, which leads to cohesion - the tendency of like molecules to stick together. This cohesive force is responsible for water's high surface tension, allowing it to form a curved surface that can resist deformation. Hydrogen bonding also enables water to undergo capillary action, where the cohesive forces and adhesive forces between water and the walls of a narrow tube or pore draw the water upwards against the force of gravity.
• Describe how the unique structure of water molecules, facilitated by hydrogen bonding, contributes to water's physical and chemical properties.
  • The hydrogen bonding between water molecules allows them to form a tetrahedral network of intermolecular attractions. This gives water a higher boiling point compared to other similar molecules, as more energy is required to overcome the hydrogen bonds and vaporize the liquid. The hydrogen-bonded network also contributes to water's high surface tension and ability to undergo capillary action. Additionally, the polarity and hydrogen bonding of water make it an excellent solvent for many ionic and polar compounds, enabling important chemical and biological processes.
• Evaluate the role of hydrogen bonding in the structure and function of important biological macromolecules, such as DNA and proteins.
  • Hydrogen bonding is essential for the structural integrity and functional properties of many biological macromolecules. In DNA, hydrogen bonds between the nitrogenous bases (adenine-thymine and guanine-cytosine) hold the two strands together, allowing for the storage and transmission of genetic information. In proteins, hydrogen bonds between the carbonyl and amino groups of the peptide backbone, as well as between side chains, stabilize the secondary and tertiary structures necessary for proper protein folding and function. Without the stabilizing influence of hydrogen bonding, these critical biomolecules would not be able to adopt and maintain their complex, biologically active conformations.

Related terms

Dipole-Dipole Interactions: Attractive forces that occur between polar molecules with a slight positive and negative charge separation.

Cohesion:

The intermolecular attractive forces that hold together like molecules, such as water molecules, resulting in surface tension and capillary action.

Adhesion:

The intermolecular attractive forces that occur between unlike molecules, such as water and other surfaces, leading to phenomena like capillary action.