Problem 54 - A Complete Resource Book in Chemistry for JEE Main

Question

Primary nitro compounds react with nitrous acid ts form nitrolic acids which dissolve in \(\mathrm{NaOH}\) giving (a) red solution (b) blue solution (c) vellow solution (d) colourless solution

Step-by-Step Solution

Answer

(a) red solution

Step 1: Identify the Reaction

Primary nitro compounds react with nitrous acid, \[\text{R}-\text{NO}_2 + \text{HNO}_2 \rightarrow \text{R}-\text{C}(=N-OH)(NO_2)\]This is the formation of nitrolic acids.

Step 2: Determine the Solubility in Sodium Hydroxide

Nitrolic acids dissolve in sodium hydroxide (NaOH) to form corresponding salts that exhibit a color change. The resulting solution color often serves as an indication of the type of compound formed.

Step 3: Analyze the Resultant Color

When nitrolic acids dissolve in NaOH, they typically form a red-colored solution. This is characteristic of the reaction between nitrolic acids and NaOH.

Key Concepts

Nitrous Acid Reaction

The reaction of primary nitro compounds with nitrous acid is an important chemical transformation. This reaction typically features a nitro group, \(- ext{NO}_2\), that interacts with nitrous acid (\( ext{HNO}_2 \)). This process leads to the formation of nitrolic acids.
The reaction can be represented as:

• \( ext{R}- ext{NO}_2 + ext{HNO}_2 ightarrow ext{R}- ext{C}(=N-OH)(NO_2) \)

Where \( ext{R}\) symbolizes an organic group.
This transformation is essential as it alters the properties of the original compound. The presence of nitrous acid enables new reactions and further chemical explorations, making it a fundamental concept in organic chemistry.

Nitrolic Acids

Nitrolic acids are a unique class of organic compounds resulting from primary nitro compounds reacting with nitrous acid. These compounds are characterized by their distinctive structure: \( ext{R}- ext{C}(=N-OH)(NO_2)\).
The formation of nitrolic acids is noteworthy because it introduces new functional groups into the compound. These groups can lead to further chemical properties and reactivities.
Nitrolic acids have varied applications, especially in synthetic chemistry, where they act as intermediates in producing valuable compounds. Their structural uniqueness opens pathways for complex reactions, enabling chemists to create innovative solutions.

Sodium Hydroxide Solubility

The solubility of nitrolic acids in sodium hydroxide (NaOH) is a crucial chemical behavior. When nitrolic acids are introduced to NaOH, they dissolve to form corresponding salts.
This solubility is pivotal for determining the specific characteristics of nitrolic acids. By dissolving in NaOH, chemists not only learn about the solubility properties but also observe specific color changes that reveal deeper insights into the nature of the compounds involved. These observations are often crucial for identifying and confirming chemical structures.

Color Change in Solutions

One interesting outcome of dissolving nitrolic acids in sodium hydroxide is the observed color change. When nitrolic acids dissolve in NaOH, they commonly form a red-colored solution.
This color change is not just aesthetic; it provides vital information about the nature of the dissolved compounds.
Color changes are used extensively in chemistry to serve as indicators, helping scientists understand the chemical environment and confirming the presence or absence of certain functional groups. The red color, in this case, is characteristic of the interaction between nitrolic acids and NaOH, signifying the successful formation of specific compounds in the mixture.