Hydration and Other Acid-Catalyzed Additions of Oxygen Nucleophiles

Hydration and Other Acid-Catalyzed Additions of Oxygen Nucleophiles 

SECTION 4.2. HYDRATION AND OTHER ACID-CATALYZED ADDITIONS OF OXYGEN NUCLEOPHILES 

Other nucleophilic species can be added to double bonds under acidic conditions. A fundamental example is the hydration of alkenes in strongly acidic aqueous solution  

Addition of a proton occurs to give the more substituted carbocation and addition is regioselective, in accord with Markownikoff s rule. A more detailed discussion of the reaction mechanism is given in Section 6.2 of Part A. The reaction is occasionally applied to the synthesis of tertiary alcohols  

Because of the strongly acidic and rather vigorous conditions required to effect hydration of most alkenes, these conditions are only applicable to molecules that have no acid-sensitive functional groups. Also, because of the involvement of cationic intermediates, rearrangements can occur in systems where a more stable cation would result by aryl, alkyl, or hydrogen migration. A much milder and more general procedure for alkene hydration is discussed in the next section. 

Addition of nucleophilic solvents such as alcohols and carboxylic acids can be effected by using strong acids as catalysts.10 

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