Problem 52 - A Complete Resource Book in Chemistry for JEE Main

Question

Consider the following reaction: \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NO}_{2} \stackrel{\mathrm{Sn} / \mathrm{HCl}}{\longrightarrow} \mathrm{X} \stackrel{\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COCl}}{\longrightarrow} \mathrm{Y}+\mathrm{HCl}\) The product \(Y\) is (a) azobenzene (b) acetanilide (c) benzanilide (d) hydrazobenzene

Step-by-Step Solution

Answer

The product Y is benzanilide (c).

Step 1: Identify the Starting Material

The reaction starts with nitrobenzene, denoted as \( \text{C}_6\text{H}_5\text{NO}_2 \). The first step involves a reduction reaction.

Step 2: Determine the First Reaction

When nitrobenzene (\( \text{C}_6\text{H}_5\text{NO}_2 \)) is treated with Sn/ HCl, it undergoes reduction to form aniline (\( \text{C}_6\text{H}_5\text{NH}_2 \)). This is a common reduction process where the nitro group is converted to an amine group.

Step 3: Examine the Second Reaction

The intermediate product aniline (\( \text{C}_6\text{H}_5\text{NH}_2 \)), is then treated with benzoyl chloride (\( \text{C}_6\text{H}_5\text{COCl} \)). This reaction is an acylation, where the amine group is acylated to form a benzamide.

Step 4: Identify Final Product Y

The acylation of aniline with benzoyl chloride results in the formation of benzanilide (\( \text{C}_6\text{H}_5\text{NHCOC}_6\text{H}_5 \)) and hydrochloric acid (HCl) as a byproduct. This identifies compound Y as benzanilide.

Key Concepts

Nitrobenzene Reduction

In organic chemistry, reduction refers to a chemical reaction that involves the gain of electrons. This often results in the conversion of functional groups into different, often less oxidized, forms. Nitrobenzene, with the chemical formula \( \text{C}_6\text{H}_5\text{NO}_2 \), contains a nitro group (\(-\text{NO}_2\)). When nitrobenzene undergoes reduction with a reducing agent like tin \( (\text{Sn}) \) in the presence of hydrochloric acid \( (\text{HCl}) \), the result is aniline (\( \text{C}_6\text{H}_5\text{NH}_2 \)).Reduction of nitrobenzene is a well-known reaction in organic chemistry due to its effectiveness in transforming a nitro group to an amino group \( (-\text{NH}_2) \).

• The reaction transforms \( \text{C}_6\text{H}_5\text{NO}_2 \) into \( \text{C}_6\text{H}_5\text{NH}_2 \).
• This involves the addition of hydrogen atoms and the loss of oxygen atoms from the nitro group.
• Aniline, the product of this reaction, serves as an important intermediate for further chemical processes.

This reduction is crucial as it lays the foundation for subsequent reactions like acylation.

Acylation Reaction

Acylation is a significant chemical process in organic chemistry, where an acyl group is introduced into a compound. After reducing nitrobenzene to aniline, the next step involves an acylation reaction by treating aniline with benzoyl chloride \( \text{C}_6\text{H}_5\text{COCl} \).This reaction specifically acylates the amine group on aniline.

• The acyl group from benzoyl chloride attaches to the nitrogen atom of the amine group in aniline, forming a benzamide linkage.
• This transformation turns aniline into a derivative known as benzanilide \( \text{C}_6\text{H}_5\text{NHCOC}_6\text{H}_5 \).
• Benzanilide is produced along with hydrochloric acid \( \text{HCl} \) as a byproduct.

In organic synthesis, acylation is used to modify functional groups, enhancing the properties of the resulting compounds, in this case, forming a stable amide bond.

Aniline to Benzanilide Conversion

The conversion of aniline to benzanilide showcases a typical synthesis path in organic chemistry. This transformation highlights the value of sequential reactions to modify the structure and properties of organic molecules.The process begins with the formation of aniline through the reduction of nitrobenzene. Aniline (\( \text{C}_6\text{H}_5\text{NH}_2 \)) is then subjected to an acylation reaction using benzoyl chloride (\( \text{C}_6\text{H}_5\text{COCl} \)).

• During the acylation, the amine group of aniline forms an amide bond with the acyl group from benzoyl chloride.
• This results in the formation of a new compound, benzanilide (\( \text{C}_6\text{H}_5\text{NHCOC}_6\text{H}_5 \)).
• The reaction showcases the creation of a more complex and structured molecule through chemical modifications.
• The production of benzanilide demonstrates the integration of amines in the synthesis of amides, a common class of reactions in organic chemistry.

This conversion is pivotal for students and chemists alike as it illustrates the practical applications of basic concepts like reduction and acylation in organic synthesis.