Hydrogen Bonds

Definition

Hydrogen bonds are a type of dipole-dipole attraction that occurs between a hydrogen atom covalently bonded to a highly electronegative atom, such as fluorine, oxygen, or nitrogen, and another nearby highly electronegative atom. These bonds are relatively weak compared to covalent or ionic bonds, but they play a crucial role in the structure and properties of many substances, especially water and biological macromolecules.

5 Must Know Facts For Your Next Test

1. Hydrogen bonds are responsible for the high boiling point of water compared to other similar-sized molecules.
2. Hydrogen bonds are critical for the secondary and tertiary structures of proteins, allowing them to fold into complex, functional shapes.
3. Hydrogen bonds are a major factor in the stability of DNA double helix structure, where they form between the base pairs.
4. Hydrogen bonds contribute to the cohesive nature of liquid water, allowing it to have a high surface tension and act as a universal solvent.
5. Hydrogen bonds play a role in the solid state of matter, as they can lead to the formation of crystalline structures in certain compounds.

Review Questions

• Explain how hydrogen bonds contribute to the unique properties of water.
  • Hydrogen bonds are responsible for many of water's distinctive properties, such as its high boiling point, surface tension, and ability to act as a universal solvent. The hydrogen bonds between water molecules create a cohesive network that requires a significant amount of energy to break apart, leading to water's high boiling point. Additionally, hydrogen bonds contribute to water's high surface tension and allow it to dissolve a wide range of polar and ionic substances.
• Describe the role of hydrogen bonds in the structure and stability of biological macromolecules.
  • Hydrogen bonds are critical for the secondary and tertiary structures of proteins, as they allow the polypeptide chains to fold into complex, functional shapes. Hydrogen bonds also stabilize the double-helix structure of DNA by forming between the base pairs. Without these hydrogen bonds, the intricate structures of these important biomolecules would not be possible, and their biological functions would be severely compromised.
• Analyze how hydrogen bonds contribute to the solid state of matter in certain compounds.
  • $$\text{In the solid state, hydrogen bonds can lead to the formation of crystalline structures in some compounds.}\text{For example, in ice, the hydrogen bonds between water molecules result in a hexagonal crystal structure that is less dense than liquid water, causing ice to float.}\text{Hydrogen bonds also play a role in the solid state of other compounds, such as hydrogen fluoride and ammonia, where they contribute to the stability and packing of the crystal lattice.}\text{The strength and directionality of hydrogen bonds can significantly influence the physical properties and phase behavior of these solid-state materials.}$$

Related terms

Dipole-Dipole Interaction: An attractive force that occurs between partially positively and partially negatively charged regions of different molecules or parts of the same molecule.

Electronegativity: The ability of an atom to attract shared electrons in a chemical bond to itself, leading to the development of partial positive and negative charges.

Covalent Bond: A strong chemical bond formed by the sharing of electrons between two atoms.