Bond Cleavage or Bond Fission | Reaction Mechanism |

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.

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