Breaking the covalent bond of the compound is called bond cleavage/bond fission.
Two types :
Homolysis or Homolytic bond fission
- Also called Symmetrical cleavage or non-polar bond cleavage .
- In this , bond is broken in such a way that each resulting species gets its own electron.
- Bond cleavage occurs between atoms having nearly equal electronegativity.
- As a result of homolytic fission, neutal species with unpaired electrons are formed, called Free radicals.
Conditions for homolysis
- High temperature.
- Electricity
- Light
- peroxide
- Non- Polar substrate
- Non- polar solvent ( like CCl4, CS2 )
Heterolysis or Heterolytic bond fission
- Also called unsymmetrical bond fission.
- Covalent bond is broken in such a way that one species is deprived of its own electron, while other gains electrons.
- Occurs in bond between two atoms of having significant difference in electronegativity.
- Formation of opposite charged species takes place.
- Resultant species are called Carbocation and Carbanion.
Conditions for Heterolysis
- Polar nature of bond
- Polar solvents like H2O, HCOOH of high dielectric constant.
- Low temperature.
Note: Free radicals, carbocation and carbanion are called reactive intermediate.