Bouveault–Blanc reduction
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The Bouveault–Blanc reduction is a chemical reaction in which an ester is reduced to primary alcohols using absolute ethanol and sodium metal.
General
Sodium metal is a one-electron reducing agent. Four equivalents of sodium are required to fully reduce each ester. Ethanol serves as a proton source. The reaction produces sodium alkoxides, according to the following stoichiometry:
- RCOOR' + 6 Na + 4 CH3CH2OH → RCH2ONa + R'ONa + 4 CH3CH2ONa
In practice, considerable sodium is consumed by the formation of hydrogen. For this reason, an excess of sodium is often required. Because the hydrolysis of sodium is rapid, not to mention dangerous, the Bouveault-Blanc reaction requires anhydrous ethanol.
Consistent with this mechanism, sodium-ethanol mixtures will also reduce ketones to secondary alcohols.
Although lithium aluminium hydride is the choice reducing agent in reducing esters to alcohols, for the hobby chemist, this reagent is expensive and hard to come by. As such, the Bouveault–Blanc reduction may be used if other alternatives are not available.
