Esters of Nitric, Sulfuric, and Phosphoric Acid

The structures of nitric, sulfuric, and phosphoric acid are shown below. The polyprotic acids, sulfuric acid and phosphoric acid, contain two and three hydroxyl groups, respectively. Thus, mono- and diesters can form from sulfuric acid and mono-, di-, and triesters from phosphoric acid. 

Although esters can be formed by direct reaction of an acid with an alcohol, they are more commonly formed using a derivative of an add called an acid chloride. Two acid chlorides of sulfuric acid-chlorosulfonic acid and sulfuryl chloride- are used to prepare esters. 

We recall that alcohols react with sulfonyl chlorides—the acid chlorides of sulfonic acids—to form sulfonates (Section 9.3). We now recognize that these alcohol derivatives are esters of an organic analog of sulfuric add. 

Alcohols react with / -toluenesulfonyl chloride to give useful synthetic intermediates called toluene-sulfonates, or tosylates. The/ -toluenesulfonate ion, a weak base, is an excellent leaving group. Methyl, primary, and secondary tosylates undergo S displacement reactions with nucleophiles. They also react with strong bases in E2 reactions. 

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