Problem 110 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following reactions result in the formation of amines? (a) (b) \(\mathrm{C}_{6} \mathrm{H}_{3}-\mathrm{NC} \stackrel{\mathrm{H}^{*} \mid \mathrm{H}_{2} \mathrm{O}}{\longrightarrow}\) (c) \(\mathrm{CH}_{3}-\mathrm{CH}_{2}-\mathrm{N}=\mathrm{C}=\mathrm{O} \stackrel{\text { aq. } \mathrm{KOH}}{\longrightarrow}\) (d) \(\mathrm{CH}_{3}-\mathrm{COOH}+\mathrm{HN}_{3} \stackrel{\text { conc. } \mathrm{H}_{2} \mathrm{SO}_{4}}{\longrightarrow}\)

Step-by-Step Solution

Answer

Reactions (b) and (d) result in the formation of amines.

Step 1: Understanding Amines

Amines are organic compounds that contain a nitrogen atom bonded to alkyl or aryl groups. They have the general formula R₃N, where R can be a hydrogen or carbon-containing substituent. Our goal is to identify reactions that result in the formation of such compounds.

Step 2: Analysis of Reaction (a)

Reaction (a) is not provided, so we will focus on the other given reactions instead.

Step 3: Analyzing Reaction (b)

Reaction (b) involves the reaction of an organic nitrile, ext{C}_{6} ext{H}_{3}- ext{NC}, with water and an unspecified catalyst represented by H*. This is a typical hydrolysis reaction, which can form amines as the nitrile group is converted into an amine. Thus, this reaction may result in the formation of an amine.

Step 4: Analyzing Reaction (c)

Reaction (c) involves the reaction of ext{CH}_{3}- ext{CH}_{2}- ext{N}= ext{C}= ext{O} with aqueous KOH. This type of reaction typically leads to the formation of an amide, not an amine, as the carbodiimide group (N=C=O) with base generally leads to conversion to a different functionality.

Step 5: Analyzing Reaction (d)

Reaction (d) involves the conversion of ext{CH}_{3}- ext{COOH}+ ext{HN}_{3} with conc. ext{H}_{2} ext{SO}_{4}. This is the Schmidt reaction, a known method for converting carboxylic acids to amines by the reaction with hydrazoic acid (HN₃) under acidic conditions. Therefore, this reaction results in the formation of an amine.

Step 6: Conclusion and Result

Based on the analysis of each reaction, reactions (b) and (d) lead to the formation of amines.

Key Concepts

Hydrolysis of Nitriles

The hydrolysis of nitriles is an important reaction in organic chemistry, particularly when aiming to generate amines from nitrile compounds. During this process, the triple-bonded nitrogen in a nitrile group (13C13N) is converted into an amine. This is typically accomplished using water and an acid or base catalyst. Such reaction converts the nitrile group (13C13N) into a primary amine (13C13NH2) with the intermediate formation of an amide.

Key steps include:

• The nitrile group undergoes hydrolysis, initially forming an amide.
• Further addition of water molecules converts the amide to an amine.
  

This transformation is valuable for introducing nitrogen into an organic molecule and is particularly useful for creating aliphatic amines, which are used extensively in pharmaceuticals and other industrial applications. To summarize, hydrolysis of nitriles is an essential process to consider when exploring pathways for amine synthesis.

Schmidt Reaction

The Schmidt reaction is an intriguing organic transformation allowing the conversion of carboxylic acids into amines. This reaction can be facilitated by reacting a carboxylic acid with hydrazoic acid (13HN2) in an acidic medium.

Important aspects of the Schmidt reaction include:

• The reaction takes place under acidic conditions, often with concentrated sulfuric acid acting as both a proton source and dehydrating agent.
• A key step in this reaction involves the formation of an acyl azide intermediate, which rearranges and decomposes to afford an isocyanate.
• Subsequent hydrolysis of the isocyanate eventually produces the desired amine product.
  

Overall, the Schmidt reaction is a powerful and elegant method for synthesizing amines from readily available carboxylic acids. Given the conversion efficiency, it is highly valued in synthetic routes, particularly useful in producing aromatic amines, which serve as crucial intermediates in dyes and pharmaceuticals.

Organic Chemistry Reactions

Organic chemistry reactions are foundational to understanding the complex transformations that molecules undergo. They involve formal processes by which chemical substances are transformed into different chemical compounds. Learning these reactions is key to mastering organic synthesis.

Key areas of organic chemistry reactions include:

• **Substitution Reactions**: Where one atom or group of atoms in a molecule is replaced by another atom or group.
• **Addition Reactions**: Typically involve breaking of multiple bonds (like double or triple bonds), allowing atoms to "add" to the molecule.
• **Elimination Reactions**: These reactions involve the removal of two atoms or groups from a molecule, usually resulting in the formation of a double bond.

Organic chemistry reactions are not just limited to substitutions, additions, or eliminations. They include a multitude of other transformation types, each with unique mechanisms and outcomes, such as rearrangement and oxidation-reduction reactions.
Overall, understanding these transformations allows chemists to design and engineer new molecules, which can be applied across fields like material science, pharmacology, and biotechnology.