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12 Reactions of Alkenes Alkenes are reactive and synthetically useful molecules. Their reactivity originates from the electrons in the bond. They are on the average further away from (and therefore electrostatically less tightly held to) the carbon nuclei than are electrons in σ bonds. As a result, they are "available" in a "Lewis base" sense, somewhat like the lone pair electrons on the oxygen of water or the nitrogen of ammonia. As you will see, attachment of an electrophile to these basic electrons has the effect of breaking the TT bond and is the first step in many reactions of alkenes, additions. Many of these addition reactions are known, and they allow conversion of alkenes to other organic molecules, including ones we've seen before (haloalkanes and alcohols) as well as new ones. These additions expand the scope of our synthetic possibilities significantly. Therefore, an updated Functional Group Interconversions chart is presented in this chapter of the study guide. Outline of the Chapter 12-1 Thermodynamic Feasibility of Addition Reactions 12-2 Hydrogenation of Alkenes 12-3 through 12-7 Electrophilic Additions to Alkenes The largest group of reactions characteristic of alkenes. 12-8 Regio- and Stereoselective Hydration of Alkenes by Hydroboration Another functional group interconversion involving addition. 12-9 Diazomethane, Carbenes, and Cyclopropane Synthesis Preparing three-membered rings. 12-10, 12-11, 12-12 Oxidation of Alkenes Additions of oxygen-containing electrophiles. 12-13 Radical Additions to Alkenes A new kind of mechanism for alkene reactions: radical additions. 12-14, 12-15 Dimerization, Oligomerization, and Polymerization of Alkenes Reactions of, mainly, industrial use. Or, "where everything in your kitchen that you don't eat comes from." 12-16 Ethene in Industry 12-17 Alkenes in Nature 237