How Organic Reactions Occur:Mechanisms All chemical reactions involve bond breaking and bond making Two ways a covalent two-electron bond can break: 1.Symmetrical or Homolytic One electron remains A·+B with each product Half-headed arrow,“fishhook”, fragment indicates movement of one 2.Unsymmetrical or Heterolytic electron Both bonding electrons remain with one A:日 A++:B product fragment, Full-headed arrow indicates leaving the other with movement of two electrons a vacant orbitalAll chemical reactions involve bond breaking and bond making Two ways a covalent two-electron bond can break: 1. Symmetrical or Homolytic ▪ One electron remains with each product fragment 2. Unsymmetrical or Heterolytic ▪ Both bonding electrons remain with one product fragment, leaving the other with a vacant orbital Half-headed arrow, “fishhook”, indicates movement of one electron Full-headed arrow indicates movement of two electrons How Organic Reactions Occur: Mechanisms