Q.D. Homolysis and heterolysis

A covalent bond can break in two ways. Homolytic cleavage (homolysis) splits the shared electron pair evenly, one electron to each previously-bonded atom (shown with a half-headed 'fish-hook' curved arrow), producing two neutral free radicals -- reactive species carrying one unpaired electron each, sp2 hybridised with trigonal planar geometry at a carbon radical, stability order tert-butyl (3°) > isopropyl (2°) > ethyl (1°) > methyl; favoured by UV light, peroxides, or heat. Heterolytic cleavage (heterolysis) instead sends both shared electrons to just the more electronegative of the two bonded atoms (shown with a full double-headed curved arrow), producing a cation and an anion; when carbon loses the electron pair it becomes a carb …