Bouveault-Blanc Reduction: Mechanism & Examples | Chemca

Organic Chemistry

Bouveault-Blanc Reduction

By Chemca Editorial Team • Last Updated: January 2026 • 7 min read

The Bouveault-Blanc Reduction is a classic method used to reduce esters to primary alcohols using metallic Sodium ($Na$) in the presence of an alcohol (typically absolute Ethanol). Before the discovery of Lithium Aluminum Hydride ($LiAlH_4$), this was the primary method for reducing esters.

1. General Reaction

An ester reacts with sodium and ethanol to yield two alcohol molecules: one corresponding to the acyl group (acid part) and one corresponding to the alkoxy group.

$$ R-COOR' + 4[H] \xrightarrow{Na / C_2H_5OH} \underbrace{R-CH_2OH}_{\text{From Acid Part}} + \underbrace{R'-OH}_{\text{From Alcohol Part}} $$

Conditions:

Substrate: Ester ($RCOOR'$), Aldehyde, or Ketone.
Reagent: Sodium metal + Ethanol ($Na/EtOH$).
Mechanism: Single Electron Transfer (SET).

2. Detailed Mechanism

The reaction proceeds via a radical-anion mechanism involving the transfer of electrons from Sodium.

Step 1: Single Electron Transfer

Sodium donates one electron to the carbonyl carbon of the ester, forming a radical anion.

$$ Na \rightarrow Na^+ + e^- $$ $$ R-C(=O)-OR' + e^- \rightarrow [R-\dot{C}-O^-]-OR' $$

Step 2: Protonation

The radical anion accepts a proton from ethanol ($EtOH$) at the oxygen atom.

$$ [R-\dot{C}-O^-]-OR' + EtOH \rightarrow [R-\dot{C}-OH]-OR' + EtO^- $$

Step 3: Elimination of Alkoxide

Another electron transfer and subsequent elimination of the alkoxide group ($R'O^-$) leads to the formation of an aldehyde intermediate.

$$ \dots \rightarrow R-CHO + R'O^- $$

Step 4: Reduction of Aldehyde

The aldehyde formed is immediately reduced by sodium and ethanol (similar steps: electron transfer $\to$ protonation) to form the final Primary Alcohol ($RCH_2OH$).

3. Examples

A. Reduction of Ethyl Acetate

Ethyl Acetate yields Ethanol (from both parts).

$$ CH_3COOC_2H_5 \xrightarrow{Na/EtOH} CH_3CH_2OH + C_2H_5OH $$

(Product is 2 moles of Ethanol)

B. Reduction of Methyl Benzoate

Yields Benzyl Alcohol and Methanol.

$$ C_6H_5COOCH_3 \xrightarrow{Na/EtOH} C_6H_5CH_2OH + CH_3OH $$

4. Comparison with $LiAlH_4$

Feature	Bouveault-Blanc ($Na/EtOH$)	Lithium Aluminum Hydride ($LiAlH_4$)
Cost	Low (Inexpensive)	High (Expensive)
Safety	Requires handling Sodium metal	Pyrophoric, reacts violently with water
Selectivity	Does not reduce isolated $C=C$	Does not reduce isolated $C=C$

5. Modern Application

While $LiAlH_4$ is standard in labs, Bouveault-Blanc is still relevant for large-scale industrial processes where cost is a major factor.

Bouveault-Blanc Quiz

Test your concepts on Ester reduction. 10 MCQs with explanations.

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