Problem 10 - A Complete Resource Book in Chemistry for JEE Main

Question

Hinsberg reagent is (a) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NO}\) (b) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{~N}_{2} \mathrm{Cl}\) (c) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{2} \mathrm{Cl}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{3} \mathrm{H}\)

Step-by-Step Solution

Answer

The Hinsberg reagent is (c) \( \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{2} \mathrm{Cl} \).

Step 1: Understanding Hinsberg Reaction

The Hinsberg reaction is a method used to distinguish between primary, secondary, and tertiary amines. It uses Hinsberg reagent, which is a specific chemical compound.

Step 2: Identify Chemical Formula

Hinsberg reagent is specifically benzenesulfonyl chloride, which has the chemical formula C_{6} H_{5} SO_{2} Cl. This compound reacts differently with different types of amines.

Step 3: Match with Options

From the options given, (c) C_{6} H_{5} SO_{2} Cl corresponds to the chemical formula for Hinsberg reagent.

Key Concepts

Primary Amines

Primary amines are organic compounds that contain a nitrogen atom connected to only one carbon-based group and two hydrogen atoms. The general formula for primary amines is \ \( RNH_2 \ \), where \ \ R \ \ represents an alkyl or aryl group. Primary amines can participate in a variety of reactions due to their highly reactive nature.
When subjected to the Hinsberg test with benzenesulfonyl chloride, primary amines form a sulfonamide which is soluble in an alkaline solution but becomes insoluble upon acidification. This reaction helps to differentiate them from secondary and tertiary amines.

• Utilized widely in pharmaceuticals, textiles, and dyes.
• Common examples include methylamine and ethylamine.
• React readily due to the lone electron pair on nitrogen, serving as a nucleophile.

Secondary Amines

Secondary amines are characterized by a nitrogen atom bonded to two carbon-based groups and one hydrogen atom. These compounds have the general formula \ \( R_2NH \ \). As with primary amines, the recognition of secondary amines is crucial in organic chemistry.
They react differently in the Hinsberg test. When treated with benzenesulfonyl chloride, they form a sulfonamide but remain insoluble in an alkaline solution. This insolubility distinguishes them from primary amines.

• Secondary amines often appear as precursors in organic synthesis.
• Examples include dimethylamine and diethylamine.
• The two R groups can vary, making them versatile in their reactivity.

Tertiary Amines

Tertiary amines have a nitrogen atom bonded to three carbon-containing groups and no hydrogen atoms directly attached. Their formula can be represented as \ \( R_3N \ \).
These amines behave quite differently compared to primary and secondary amines in chemical reactions. In the Hinsberg test, tertiary amines do not react with benzenesulfonyl chloride, providing a clear means of identification.

• Widely used as catalysts, solvents, and emulsifiers.
• Triethylamine and tripropylamine are common examples.
• The lack of hydrogen atoms on nitrogen influences their reaction pathways.

Benzenesulfonyl Chloride

Benzenesulfonyl chloride is a powerful organic compound widely used in chemical reactions. It serves as the key reagent in the Hinsberg test for distinguishing amines. Its chemical formula is given by \ \( C_6H_5SO_2Cl \ \).
During the Hinsberg reaction, it forms a sulfonamide when it reacts with amines. The different behavior of primary, secondary, and tertiary amines upon reacting with benzenesulfonyl chloride reveals crucial information about their structure.

• Used in the production of sulfonamides in medicinal chemistry.
• Plays a significant role in organic synthesis and biochemical assays.
• Requires careful handling due to its reactive chloride group.

Chemical Reactions in Organic Chemistry

Chemical reactions in organic chemistry involve the transformation of organic compounds through the process of making or breaking chemical bonds. Reactions such as those with benzenesulfonyl chloride illustrate the principles of organic synthesis and mechanism studies.
In the context of the Hinsberg test, understanding the reaction pathways provides insights into the structures and reactivities of different amines. This knowledge is vital for the development of pharmaceuticals, polymers, and other chemical products.

• Cover diverse areas like substitution, elimination, and addition reactions.
• Enable the synthesis of complex organic molecules crucial in various industries.
• Highlight the importance of reaction selectivity and specificity.