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Unformatted text preview: 12/11/2010 1 Chapter 10 Radical Reactions Chapter 10 2 Introduction Homolytic bond cleavage leads to the formation of radicals (also called free radicals) Radicals are highly reactive, short-lived species (like carbocations) Single-barbed arrows are used to show the movement of single electrons Production of Radicals Homolysis of relatively weak bonds such as O-O or X-X bonds can occur with addition of energy in the form of heat or light H O O H HO OH + Chapter 10 3 Radicals in Nature Photochemistry of NO in the air ultimately leads to HO • , a very aggressive radical Oxygen is a diradical Superoxide, is a very damaging radical produced during oxidative metabolism Destroyed by superoxide dismutase O O O O Chapter 10 4 Reactions of Radicals Radicals tend to react in ways that lead to pairing of their unpaired electron Hydrogen abstraction is one way a halogen radical can react to pair its unshared electron THIS WILL LEAD TO THE FORMATION OF A NEW RADICAL CAPTURING REACTIVE RADICALS TO MAKE LESS REACTIVE RADICALS is BIG BUSINESS BUTYLATED HYDROXYTOLUENE, VITAMIN E O O O Before After 12/11/2010 2 Chapter 10 5 Homolytic Bond Dissociation Energies Atoms have higher energy (are less stable) than the molecules they can form The formation of covalent bonds is exothermic Breaking covalent bonds requires energy ( i.e. is endothermic) I 2 152.2 kJ/mol; The homolytic bond dissociation energy is abbreviated...
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This note was uploaded on 05/16/2011 for the course CHEM BIO 20a3 taught by Professor Stover during the Fall '10 term at McMaster University.
- Fall '10