Problem 22 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Bouveault-Blanc reduction reaction involves: (a) Reduction of an acyl halide with \(\mathrm{H}_{2} / \mathrm{Pd}\) (b) Reduction of an anhydride with \(\mathrm{LiAlH}_{4}\) (c) Reduction of an ester with \(\mathrm{Na} / \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (d) Reduction of a carbonyl compound with \(\mathrm{Na} / \mathrm{Hg}\) and \(\mathrm{HCl}\).

Step-by-Step Solution

Answer

(c) Reduction of an ester with \(\mathrm{Na} / \mathrm{C}_{2}\mathrm{H}_{5}\mathrm{OH}\).

Step 1: Understand the Reaction

The Bouveault-Blanc reduction reaction is named after Louis Bouveault and Gustave Louis Blanc and is specifically a reduction of esters to alcohols using sodium and ethanol, which aligns with option (c). Other options involve different reactants and reagents that do not pertain to the Bouveault-Blanc reduction.

Step 2: Evaluate Each Option

(a) Reduction of an acyl halide with \( \mathrm{H}_{2} / \mathrm{Pd} \) involves hydrogenation and is unrelated to the Bouveault-Blanc reaction. (b) Reduction of an anhydride with \( \mathrm{LiAlH}_{4} \) uses a complex hydride as a reducing agent, again unrelated. (c) Reduction of an ester with \( \mathrm{Na} / \mathrm{C}_{2}\mathrm{H}_{5}\mathrm{OH} \) is specifically the Bouveault-Blanc reduction. (d) Reduction of a carbonyl compound with \( \mathrm{Na} / \mathrm{Hg} \) and \( \mathrm{HCl} \) is known as Clemmensen reduction.

Step 3: Select the Correct Answer

Since the Bouveault-Blanc reduction involves the conversion of esters into alcohols using sodium and ethanol, the correct answer is option (c).

Key Concepts

Ester Reduction

The process of ester reduction is a chemical reaction that involves transforming an ester into a different compound by removing oxygen or by adding electrons. In the context of Bouveault-Blanc reduction, the ester is reduced to an alcohol.
The ester reduction is significant because it allows for the conversion of esters, which are common in many organic compounds, into alcohols. This transformation is important in organic chemistry because alcohols are versatile and can be used for further chemical synthesis.
The application of the Bouveault-Blanc reduction, using sodium and ethanol for ester reduction, highlights the specificity of reagents in yielding desired products. The reagents interact with the ester in a way that selectively reduces it into its alcohol form without affecting other functional groups, making it a convenient method in synthetic chemistry.

Alcohol Synthesis

Alcohol synthesis is essential in organic chemistry. It allows chemists to create alcohols from various starting materials, such as esters, aldehydes, or ketones.
In the Bouveault-Blanc reduction, alcohol synthesis is achieved by the reduction of esters. When an ester undergoes reduction with sodium and ethanol, the product is an alcohol. This reaction is advantageous because it provides a direct route to synthesize alcohols, particularly primary alcohols, from more complex ester structures.
The significance of synthesizing alcohols lies in their widespread use in chemical compounds and reactions. Alcohols can act as solvents, reactants, or products in many biochemical and industrial processes. By understanding alcohol synthesis through the Bouveault-Blanc reduction, students gain insights into one of the many pathways for producing valuable alcohol compounds.

Sodium in Ethanol Reduction

In Bouveault-Blanc reduction, sodium in ethanol plays a crucial role as the reducing agent. This reduction method serves as an alternative to the use of heavier and more expensive metal hydrides like Lithium Aluminium Hydride (LiAlH₄).
The reason sodium in ethanol is effective in reduction is due to its ability to donate electrons. When sodium metal is dissolved in ethanol, it forms sodium ethoxide. This intermediate is key in transferring electrons essential for breaking down the ester bond and generating the alcohol.
The choice of using ethanol is also strategic. Ethanol is a protic solvent which helps facilitate the reaction, and its compatibility with sodium makes it an efficient partner in ester reduction. Sodium in ethanol reduction highlights an accessible and cost-effective method for the generation of alcohols from esters, illustrating the ingenuity in chemical problem-solving by using readily available materials.