Problem 38 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Carbylamine test is performed in alcoholic \(\mathrm{KOH}\) by heating a mixture of :(a) chloroform and silver powder (b) trihalogenatedmethane and a primary amine (c) an alkyl halide and a primary amine (d) an alkyl cyanide and a primary amine

Step-by-Step Solution

Answer

The carbylamine test is performed with (b) trihalogenatedmethane and a primary amine.

Step 1: Understanding Carbylamine Reaction

The Carbylamine reaction is used to identify primary amines. It involves heating a mixture of a primary amine, chloroform, and alcoholic potassium hydroxide (KOH) to produce an isocyanide, which has a characteristic unpleasant odor.

Step 2: Identifying Key Reactants

The key reactants in the Carbylamine test are a primary amine, chloroform (a trihalogenated methane), and an alcoholic KOH solution. We need to identify which option provides these reactants.

Step 3: Analyzing Each Option

- (a) Chloroform and silver powder: Does not include a primary amine. - (b) Trihalogenatedmethane and a primary amine: Takes into account chloroform as trihalogenated methane and a primary amine, fulfilling the Carbylamine reaction requirements. - (c) An alkyl halide and a primary amine: Lacks chloroform/trihalogenated methane. - (d) An alkyl cyanide and a primary amine: Also lacks chloroform/trihalogenated methane.

Step 4: Selecting the Correct Option

Based on the conditions of the Carbylamine test, option (b) provides both trihalogenatedmethane (chloroform) and a primary amine necessary for the reaction. Thus, the correct answer is (b).

Key Concepts

Primary Amine Identification

Identifying a primary amine is crucial in various chemical processes, including the Carbylamine test. A primary amine is an organic compound containing a nitrogen atom bonded to one carbon atom (other than any carbonyl carbon) and two hydrogen atoms. It is essential in the formation of isocyanides during the Carbylamine test.
In practical terms, primary amines are tested by their ability to undergo specific reactions, such as the Carbylamine test, where their presence leads to the formation of an isocyanide. This reaction is sensitive to primary amines and does not occur with secondary or tertiary amines, making it a reliable identification method.

• Primary amine structure: R-NH₂, where R is an alkyl or aryl group.
• Reactivity: Primary amines readily react under certain conditions, making them easy to test for.

This focus on reactivity helps in identifying primary amines in various chemical reactions, proving their fundamental role in organic chemistry.

Isocyanide Formation

Isocyanide formation is a key indicator in the Carbylamine test. It provides a distinctive, pungent odor, helping chemists confirm the presence of primary amines. The process involves the conversion of primary amines, chloroform, and alcoholic potassium hydroxide (KOH) into isocyanides.
The isocyanide reaction proceeds as follows:

• The primary amine reacts with chloroform (CHCl₃) in the presence of strong base, alcoholic KOH.
• Upon heating, a complex series of reactions ensue, forming the isocyanide (R-NC) and releasing water and potassium chloride.

The presence of the unpleasant isocyanide smell acts as a qualitative test for primary amines. Given its specificity, this reaction is frequently utilized in laboratories for amine detection in organic compound mixtures. The Carbylamine reaction remains versatile and vital in organic synthesis and analytical testing.

Organic Chemistry Reactions

Organic chemistry reactions, such as the Carbylamine reaction, are pivotal in transforming compounds and identifying various molecular structures. This area of chemistry focuses on the behavior of carbon-containing compounds and their interactions with other elements like hydrogen, oxygen, and nitrogen.
In the context of the Carbylamine reaction, understanding the basic principles of organic reactions helps in grasping how primary amines are converted into isocyanides. Reactions in organic chemistry often involve:

• Formation or breaking of chemical bonds between carbon and other elements.
• Presence of catalysts or conditions like temperature changes that facilitate reaction progress.

The accuracy of such reactions is influenced by factors like molecular structure and the specific reactants present. By studying organic reactions, chemists can predict outcomes, manipulate compounds, and create new materials, showcasing the invaluable role of organic chemistry in scientific innovation and practical applications.