Double Bonds

Definition

A double bond is a covalent bond in organic chemistry where two pairs of electrons are shared between two atoms, typically carbon atoms. Double bonds are an important structural feature in many organic compounds and play a crucial role in understanding and drawing chemical structures.

5 Must Know Facts For Your Next Test

1. Double bonds are more reactive than single bonds due to the presence of two shared electron pairs, making them susceptible to various chemical reactions.
2. The presence of double bonds affects the geometry and hybridization of the atoms involved, typically resulting in sp$^2$ hybridization and a trigonal planar arrangement.
3. Double bonds can participate in resonance, where the electrons are delocalized across multiple bonds, leading to increased stability and altered reactivity.
4. The length of a double bond is shorter than a single bond between the same atoms, as the shared electron pairs are more tightly held.
5. The presence of double bonds can affect the physical properties of organic compounds, such as boiling point, melting point, and solubility.

Review Questions

• Explain how the presence of double bonds affects the geometry and hybridization of the atoms involved in an organic molecule.
  • The presence of double bonds in an organic molecule leads to sp$^2$ hybridization of the carbon atoms involved. This results in a trigonal planar arrangement around the carbon atoms, with bond angles of approximately 120 degrees. The double bond consists of one sigma (\sigma) bond and one pi (\pi) bond, with the \pi bond being more reactive and susceptible to various chemical reactions.
• Describe the role of resonance in the stability and reactivity of organic compounds with double bonds.
  • Double bonds can participate in resonance, where the electrons are delocalized across multiple bonds. This delocalization of electrons leads to increased stability of the molecule, as the energy of the system is lowered. The resonance also affects the reactivity of the compound, as the electrons are not as tightly held and can be more easily involved in chemical reactions. Resonance is an important concept in understanding the behavior and properties of organic compounds with double bonds.
• Analyze how the physical properties of organic compounds, such as boiling point, melting point, and solubility, can be influenced by the presence of double bonds.
  • The presence of double bonds in organic compounds can significantly impact their physical properties. Double bonds generally increase the intermolecular forces between molecules, leading to higher boiling points and melting points compared to their saturated counterparts. Additionally, the presence of double bonds can affect the solubility of the compound, as the delocalized \pi electrons can participate in various intermolecular interactions, such as dipole-dipole interactions and \pi-stacking. These changes in physical properties due to double bonds are important considerations in understanding the behavior and applications of organic compounds.

Related terms

Covalent Bond:

A chemical bond formed by the sharing of one or more pairs of electrons between two atoms.

Hybridization:

The process of mixing atomic orbitals to form new hybrid orbitals, which determines the geometry and bond angles of a molecule.

Resonance:

The ability of certain molecules to be represented by multiple valid Lewis structures, leading to the delocalization of electrons and stabilization of the molecule.