Problem 68 - A Complete Resource Book in Chemistry for JEE Main

Question

Among the following compounds, which will react with acetone to give a product containing \(>\mathrm{C}=\mathrm{N}-\) ? 1\. \(\mathrm{C}_{6} \mathrm{H}_{3} \mathrm{NH}_{2}\) 2\. \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}\) 3\. \(\mathrm{C}_{6} \mathrm{H}_{3} \mathrm{NHC}_{6} \mathrm{H}_{5}\) 4\. \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NHNH}_{2}\) (a) 3,4 (b) \(1,3,4\) (c) 1,3 (d) 1,4

Step-by-Step Solution

Answer

(d) 1,4

Step 1: Identify the Reaction Type

The reaction in question involves the formation of a C=N bond with acetone. This typically involves condensation with a compound containing an amine group, specifically a primary amine, or a hydrazine group.

Step 2: Analyze Each Compound

Let's analyze each given compound to determine if it can react with acetone to form a C=N bond with the indicated structure:1. \(\mathrm{C}_{6} \mathrm{H}_{3} \mathrm{NH}_{2}\): This is a primary amine, which can react to form a C=N bond.2. \((\mathrm{CH}_{3})_{3} \mathrm{N}\): This is a tertiary amine, which lacks a hydrogen atom necessary for the reaction with acetone.3. \(\mathrm{C}_{6} \mathrm{H}_{3} \mathrm{NHC}_{6} \mathrm{H}_{5}\): This is a secondary amine; typically, only primary amines or hydrazines react to form a C=N bond with acetone.4. \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NHNH}_{2}\): This is a hydrazine group, which can form a C=N bond.

Step 3: Determine Reactivity with Acetone

Among the compounds described:- Compound 1 (\(\mathrm{C}_{6} \mathrm{H}_{3} \mathrm{NH}_{2}\)) is capable of forming a C=N bond.- Compound 4 (\(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NHNH}_{2}\)) can also form a C=N bond due to its hydrazine structure.

Step 4: Choose the Correct Answer

Based on the analysis above, compounds 1 and 4 will react with acetone to give a product containing a C=N bond. Therefore, the correct answer is (d) 1,4.

Key Concepts

Condensation Reaction

A condensation reaction in organic chemistry is a process where two molecules combine, resulting in the formation of a larger molecule and the loss of a small molecule such as water. This type of reaction is invaluable due to its ability to facilitate the formation of new bonds, such as C=N bonds, contributing to the complexity of organic molecules. Condensation reactions are integral in forming polymers and many macromolecules.

• Involves the combination of two substances with the elimination of a small molecule.
• Common small molecules lost include water, ammonia, or alcohol.
• The reaction often requires specific conditions to proceed, such as the presence of a catalyst or specific reagents.

This mechanism is crucial in organic synthesis, allowing chemists to build larger and more complex structures from simpler ones. Understanding condensation reactions helps predict how different organic compounds will interact and the products they may form.

Primary Amine

Primary amines are organic compounds and functional groups characterized by a nitrogen atom bonded to one carbon atom and two hydrogen atoms. Their general structure is RNH₂, where R represents an alkyl or aryl group.

• Primary amines react readily in condensation reactions with aldehydes and ketones to form imines, featuring a C=N double bond.
• The presence of a hydrogen atom attached to the nitrogen makes primary amines unlike secondary and tertiary amines, which do not react optimally due to steric hindrance or lack of hydrogen to facilitate the reaction.
• Examples include compounds like aniline (CHNH₂) where the nitrogen is directly bonded to the benzene ring, enabling unique reactivity compared to aliphatic amines.

Primary amines are significant in syntheses involving the formation of C=N bonds, which are crucial in creating various organic products with complex structures.

Hydrazine

Hydrazine compounds are characterized by two nitrogen atoms bonded directly to each other, forming an N-N bond. The basic structure is R-NHNH₂, and they are widely recognized for their ability to form C=N bonds through condensation reactions.

• A hydrazine like phenylhydrazine (CH₅NHNH₂) can react with ketones like acetone, creating a hydrazone, a type of C=N bond product.
• The presence of two nitrogen atoms makes hydrazines highly reactive, particularly with carbonyl groups, facilitating the formation of nitrogen-containing rings or chains.

Hydrazines are not only critical in organic syntheses but also find applications in various industries, including rocketry due to their highly exothermic and explosive nature. Their reactivity makes them versatile in chemical reactions where new bond formation is needed.

C=N Bond Formation

The formation of a carbon-nitrogen double bond (C=N) is a fundamental concept in organic chemistry, contributing heavily to the creation of compounds like imines and hydrazones.

• Such bond formation occurs commonly during condensation reactions where a carbonyl compound (like an aldehyde or ketone) interacts with nitrogen-containing compounds (like primary amines or hydrazines).
• The C=N bond is pivotal in biological systems and synthetic chemistry, functioning as a site for further reactions and as a part of larger structural motifs in pharmaceuticals.
• Certain conditions, such as acidic catalysts, can enhance the formation of C=N bonds, facilitating the creation of stable intermediates or final products.

The ability to form a C=N bond enables synthetic chemists to produce a variety of useful, stable compounds, including fragrances, dyes, and therapeutics, through straightforward yet powerful chemical transformations.