What Are the Characteristic Reactions of Alkenes

The most characteristic reaction of alkenes is addition to the carbon-carbon double bond in such a way that the pi bond is broken and, in its place, sigma bonds are formed to two new atoms or groups of atoms. Several examples of reactions at the carbon-carbon double bond are shown in Table 5.1, along with the descriptive name(s) associated with each. 

From the perspective of the chemical industry, the single most important reaction of ethylene and other low-molecular-weight alkenes is the production of chain-growth polymers (Greek poly, many, and meros, part). In the presence of certain catalysts called initiators, many alkenes form polymers by the addition of monomers (Greek mono, one, and meros, part) to a growing polymer chain, as illustrated by the formation of polyethylene from ethylene  

In alkene polymers of industrial and commercial importance, w is a large number, typically several thousand. We discuss this alkene reaction in Chapter 16. 

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