Q.What are Homolytic and Heterolytic cleavage? OR Define Anti-Markovnikov's rule with suitable example.
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Start your 14-day free trial to unlock the full solution →Homolytic cleavage splits a bond's electron pair evenly to give two free radicals; heterolytic cleavage gives both electrons to one fragment, producing a cation and an anion.
When a covalent bond between two atoms breaks, the shared pair of electrons can be distributed in two distinct ways:
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Homolytic (or homolysis) cleavage: The bond breaks symmetrically, and each of the two resulting fragments keeps exactly one electron from the original shared pair. This produces two electrically neutral species, each with an unpaired electron, called free radicals. This type of cleavage is favoured under conditions like heat, light (UV), or in the presence of peroxides (radical initiators), and typically occurs in non-polar solvents or the gas phase.
Example: Cl-Cl --(hν or heat)--> Cl• + Cl• (two chlorine free radicals)
It is represented in mechanisms using a single-barbed 'fish-hook' curved arrow (half-headed arrow), showing the movement of just one electron.
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Heterolytic (or heterolysis) cleavage: The bond breaks unevenly/unsymmetrically, and one of the two fragments takes BOTH electrons of the shared pair, while the other fragment gets none. This produces one positively charged species (cation, which lost the electrons) and one negatively charged species (anion, which gained both electrons). Heterolytic cleavage is favoured in polar solvents and is the basis of ionic reaction mechanisms (like SN1, SN2, electrophilic addition, etc.). …
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