Problem 63 - A Complete Resource Book in Chemistry for JEE Main

Question

Peroxide effect can be checked by the addition of sufficient amount of (a) monophenyl amine (b) diphenyl amine (c) triphenyl amine (d) pentaphenyl amine

Step-by-Step Solution

Answer

The peroxide effect can be checked by the addition of diphenyl amine (b).

Step 1: Identify the Concept

The problem asks about the peroxide effect, which is related to the inhibition of oxidation reactions by trapping radicals. Certain amines can trap these radicals, protecting substances from oxidation.

Step 2: Analyze the Options

Monophenyl amine, diphenyl amine, triphenyl amine, and pentaphenyl amine are aromatic amines with increasing numbers of phenyl groups. Typically, the ability to trap radicals increases with the number of phenyl groups due to enhanced stabilization of the amine radical formed after trapping.

Step 3: Choose the Correct Answer

Peroxide decomposition can be inhibited effectively by diphenyl amine because it has sufficient phenyl groups to stabilize the amine radical, making it an effective inhibitor. It is commonly used for this purpose in real-world applications.

Key Concepts

Free Radical Mechanism

Free radical mechanisms are pivotal in numerous chemical reactions, and they're fundamental to understanding the peroxide effect. In these reactions, a molecule splits into two free radicals. The free radicals are atoms, molecules, or ions with unpaired electrons, making them highly reactive. One key reaction where this mechanism is crucial is in polymerization, such as the creation of plastic from small monomers.

In the context of the peroxide effect, the presence of free radicals can initiate a chain reaction leading to unwanted oxidation. The peroxide effect involves the formation of radicals, typically through the decomposition of peroxides into radical species. These radicals can perpetuate a reaction chain, particularly in organic compounds, leading to degradation and undesirable changes.

Understanding this mechanistic approach helps predict and control reactions involving peroxides, where the generation and stabilization of free radicals play a central role.

Aromatic Amines

Aromatic amines, such as monophenyl amine, diphenyl amine, triphenyl amine, and pentaphenyl amine, are organic compounds characterized by one or more phenyl groups attached to their amino group. These compounds are known for their role in both industrial and biochemical applications.

Each additional phenyl group provides distinct stabilization benefits. For instance, in radical trapping, the more phenyl groups present in an amine, the more stable the radical intermediate becomes. This is due to the resonance stabilization provided by the aromatic ring, which disperses the unpaired electron's energy.

In practical scenarios, aromatic amines, especially those with multiple phenyl groups, are used to inhibit oxidation reactions by effectively trapping radicals. For example, diphenyl amine is popular due to its optimal balance between effectiveness and stability in trapping free radicals.

Radical Inhibition

Radical inhibition involves slowing down or stopping free radical reactions. This is important in preventing unwanted chemical reactions, such as oxidation, that can damage materials. Radical inhibitors achieve this by reacting with free radicals to form more stable compounds. By doing so, they prevent further chain reactions. This is essential in industries like food preservation, polymer stabilization, and the storage of chemicals, where it is critical to maintain the integrity of substances over time.

Aromatic amines are classical examples of radical inhibitors. They act efficiently because they can stabilize the radical formed during their reaction with initial free radicals. However, not all amines are equally effective. The efficacy of radical inhibition is determined by the molecular structure of the aromatic amine, with diphenyl amine being a preferred choice. It efficiently stabilizes the radical due to its molecular structure, thus inhibiting further radical chain reactions.