Moving Forward - Arrow Pushing in Organic Chemistry - page 137

Scheme 8.3 Conversion of alcohols to ethers—the Williamson ether synthesis.
While the examples presented in Schemes 8.1 and 8.2 illustrate only the formation of
alkyl bromides, it is important to recognize that halogens can be replaced through nucleo-
philic displacements. These displacements can occur via either S N 1orS N 2 mechanisms.
Regarding S N 1 reactions, ionization generally occurs under solvolytic conditions, limiting
the nucleophile to the solvent used. In the case of S N 2 reactions, the only limiting factors
relate to the relative nucleophilicities of the incoming nucleophiles compared to those of the
leaving groups. Thus, as illustrated in Figure 8.1, alkyl halides can be converted into a wide
variety of useful functional groups.
Upon further examination of the functional group transformations summarized in
Figure 8.1, there are a number of additional conversions applicable to the product functional
groups. Among these are the conversions of alcohols to ethers illustrated in Scheme 8.3.
Figure 8.2 Transformations of carboxylic acids to esters and amides.
Figure 8.3 Transformations of esters to carboxylic acids and amides.