Question

A secondary amine on reaction with Hinsberg's reagent gives (A) Primary sulphonamide, soluble in alkali (B) Secondary sulphonamide, insoluble in alkali (C) Tertiary sulphonamide, insoluble in alkali (D) Secondary sulphonamide, soluble in alkali

Short answer

The reaction of a secondary amine with Hinsberg's reagent results in a secondary sulphonamide that is insoluble in alkali. Thus, the correct answer is (B) Secondary sulphonamide, insoluble in alkali.

Step-by-step solution

Understand the reaction between amines and Hinsberg's reagent

Hinsberg's reagent, also called benzene sulfonyl chloride (C6H5SO2Cl), is commonly used to distinguish primary, secondary, and tertiary amines. The reaction between an amine and Hinsberg's reagent produces sulphonamides. Depending on the type of amine, we get primary sulphonamides, secondary sulphonamides, or tertiary sulphonamides.

Identify the given reactant as a secondary amine

In this exercise, we are given a secondary amine. A secondary amine is a compound where two organic groups are attached to the amine nitrogen atom, and one hydrogen is also bonded to the nitrogen atom. It can be represented as R1R2NH, where R1 and R2 are organic groups.

Determine the reaction product for a secondary amine with Hinsberg's reagent

When a secondary amine (R1R2NH) reacts with Hinsberg's reagent (C6H5SO2Cl), it forms a secondary sulphonamide, which can be represented as (C6H5SO2NR1R2). The hydrogen bonded to the nitrogen atom in the amine replaces the chlorine atom in the Hinsberg's reagent, leaving a secondary sulphonamide molecule. Now, let's determine the solubility of secondary sulphonamide in alkali.

Identify the solubility of secondary sulphonamide in alkali

The solubility of sulphonamides in alkali depends on the presence of an acidic hydrogen atom attached to the nitrogen atom. In secondary sulphonamide (C6H5SO2NR1R2), there is no hydrogen atom attached to the nitrogen atom, so it cannot form a salt with alkali, making it insoluble in alkali. We have now determined that the reaction between a secondary amine and Hinsberg's reagent produces a secondary sulphonamide that is insoluble in alkali. Therefore, the correct answer is: (B) Secondary sulphonamide, insoluble in alkali

Key concepts

Understanding Secondary Amines

A secondary amine is an important structure in organic chemistry. It arises when two organic groups attach to the nitrogen atom, along with a single hydrogen atom. These compounds generally appear as R₁R₂NH, where R₁ and R₂ represent organic groups. Understanding secondary amines helps in identifying how they react with various chemical reagents.

In comparison to primary amines, where the nitrogen atom is bonded with two hydrogen atoms, secondary amines have only one. This slight modification results in distinct chemical reactions. Secondary amines can maintain their structure in a variety of organic reactions, which makes them essential in synthesizing different molecules.

Sulphonamide Solubility Characteristics

Sulphonamides are products formed when amines react with certain reagents, such as Hinsberg's reagent. The solubility of these compounds in alkali largely depends on the structure of hydrogen bonds within the molecule. When dealing with secondary sulphonamides, it is crucial to understand their solubility properties.

Secondary sulphonamides, for instance, lack an acidic hydrogen attached to their nitrogen atom. This feature makes them unable to form salts in the presence of alkali, rendering them insoluble. This contrasts sharply with the behavior of primary sulphonamides, which can interact with alkali due to their available hydrogen atom. The principle of solubility here is a core concept for students to grasp in the study of amines and their derivatives.

Reactivity in Organic Chemistry Reactions

Exploring how compounds react in organic chemistry provides insight into molecular transformations. A classic example involves the reaction of secondary amines with Hinsberg's reagent. When secondary amines encounter benzene sulfonyl chloride, they create a secondary sulphonamide.

In this reaction, the sole hydrogen atom attached to the nitrogen in the secondary amine is replaced by the chloride from Hinsberg's reagent. This process forms sulphonamides, specifically secondary sulphonamides, due to the structure of the starting amine. Understanding these steps unveils how molecular rearrangements lead to the creation of new substances, a fundamental understanding in organic chemistry suitable for both academic and industrial applications.