What is the Difference Between Homolytic and Heterolytic Bond Dissociation Energy?

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The difference between homolytic and heterolytic bond dissociation energy lies in the manner in which a chemical bond is cleaved and the products formed during the process.

  • Homolytic Bond Dissociation Energy: This is the amount of energy required to dissociate a chemical bond via homolysis, where the bond is cleaved in such a way that both atoms retain one electron each, resulting in the formation of two free radicals. The energy required for homolytic fission is generally lower than that of heterolytic fission for the same bond. An example of homolytic fission can be observed in the hydrogen chloride molecule.
  • Heterolytic Bond Dissociation Energy: This is the amount of energy required to cleave a chemical bond via heterolysis, where the bond pair of electrons is not shared equally between the two atoms, and the bond is cleaved in such a way that one atom retains both electrons, resulting in the formation of a cation and an anion. The energy required for heterolytic fission is generally higher than that of homolytic fission for the same bond.

In summary, the main differences between homolytic and heterolytic bond dissociation energy are:

  1. Homolytic bond dissociation energy is associated with the formation of radicals by the cleavage of a bond.
  2. Heterolytic bond dissociation energy is associated with the formation of cations and anions by the cleavage of a bond.
  3. Homolytic bond dissociation energy is generally lower than heterolytic bond dissociation energy for the same bond.

Comparative Table: Homolytic vs Heterolytic Bond Dissociation Energy

Homolytic and heterolytic bond dissociation energies differ in the way the chemical bond is cleaved and the products formed. Here is a comparison table of the differences between the two:

Property Homolytic Bond Dissociation Energy Heterolytic Bond Dissociation Energy
Cleavage Mechanism Cleaving the bond homolytically results in the formation of radicals. Cleaving the bond heterolytically results in the formation of cations and anions.
Enthalpy Change The measured bond dissociation energies (BDE's) in tables represent homolytic cleavage. Heterolytic cleavage typically requires more energy than homolytic cleavage.
Bond Strength Homolytic cleavage usually results in a weaker bond compared to heterolytic cleavage. Heterolytic cleavage often leads to a stronger bond compared to homolytic cleavage.

When a bond dissociation energy is listed, it typically refers to the homolytic cleavage of the bond. Homolytic bond dissociation energy is associated with the formation of radicals by the cleavage of a chemical bond, while heterolytic bond dissociation energy is associated with the formation of cations and anions by the cleavage of a chemical bond.