Ethers and Epoxides

Ethers are molecules that contain an oxygen atom that is connected to two carbon substituents. Ethers can be synthesized through alcohol addition to an alkene or S_N2 or S_N1 substitution of a haloalkane. Ethers are, unlike alcohols, relatively inert and nonreactive. This limits the functionality of ethers, but it makes ethers into great protecting groups (groups that can be added to a functional group to protect it from further change and then removed at a later stage in the synthesis). While a protecting group is not a green way to achieve synthetic selectivity, they can be unavoidably necessary for successful syntheses. A special class of ethers are epoxides: oxygen atoms that make one of the atoms in a three-membered ring. The high amount of strain in an epoxide makes them much more reactive than ethers. This chapter considers the scope of ether chemistry (formation, cleavage, and protecting groups) and looks at the utility of epoxides as synthetic intermediates.