Oxymercuration Demercuration
Oxymercuration Demercuration - Related Videos
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Oxymercuration-Reduction of Alkenes
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2025
Oxymercuration–reduction of alkenes is one of the major reactions converting alkenes to alcohols. It involves the hydration of alkenes with mercuric acetate in a mixture of tetrahydrofuran and water, forming an organomercury adduct. This is followed by a demercuration step in which the adduct is reduced to an alcohol using sodium borohydride. In the mixture of water and tetrahydrofuran, tetrahydrofuran acts as a solvent dissolving the alkene and the aqueous mercuric acetate solution, while...
02:35
Ethers from Alkenes: Alcohol Addition and Alkoxymercuration-Demercuration
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2023
Overview Ethers can also be prepared from alkenes through acid-catalyzed addition of alcohols and alkoxymercuration–demercuration. Preparation of Ethers by Acid-Catalyzed Addition of Alcohol to Alkenes The acid-catalyzed addition of alcohol to an alkene involves treating the alkene with an excess of alcohol in the presence of an acid catalyst to form an ether under suitable conditions. The hydrogen will add to the less substituted carbon so that the nucleophile can attack the more substituted...
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The bridged mercurinium ion controls where the new carbon-oxygen bond forms. After mercury(II) acetate activates the alkene, water attacks the more substituted carbon. This regioselective attack places the oxygen-derived group at that carbon, while the mercury-containing portion remains attached to the other carbon until the reduction step.
Its pathway does not proceed through a free carbocation. Instead, alkene activation produces a bridged mercurinium ion, which directs water toward the more substituted carbon. Because the reaction avoids the carbocation intermediate associated with acid-catalyzed hydration, it also avoids the rearrangement pathways described for that alternative. This makes the method useful when predictable connectivity matters.
Sodium borohydride completes the transformation by reducing the organomercury intermediate formed in the first step. Specifically, it replaces the carbon-mercury bond with a carbon-hydrogen bond. The alcohol's carbon-oxygen framework has already been established during water attack, so this second step removes the mercury-containing substituent while preserving the intended hydroxyl placement.
The procedure begins by treating the alkene with mercury(II) acetate, which forms the bridged mercurinium ion. Water then attacks the more substituted carbon, producing an intermediate that contains both the alcohol functionality and a carbon-mercury bond. In the second stage, sodium borohydride reduces that bond, completing conversion of the alkene framework into the alcohol product.
Unlike acid-catalyzed hydration, this method does not require strongly acidic conditions. It uses mercury(II) acetate for alkene activation, water as the source of the oxygen-containing group, and sodium borohydride in the reduction stage. Separating these functions clarifies why the sequence first establishes regioselectivity and then replaces the carbon-mercury bond with hydrogen.
Oxymercuration-demercuration provides a route from an alkene starting material to an alcohol with Markovnikov placement while avoiding rearrangement pathways. It is useful when the target structure requires the hydroxyl group on the more substituted alkene carbon. The reaction also illustrates how electrophilic addition, regioselectivity, reagent choice, and reaction workup determine the structure of an organic product.