Problem 36 - A Complete Resource Book in Chemistry for JEE Main

Question

In organic reactions, sodium in liquid ammonia is used as ...... (a) oxidizing agent (b) reducing agent (c) hydrolyzing agent (d) precipitating agent

Step-by-Step Solution

Answer

Sodium in liquid ammonia is used as a reducing agent.

Step 1: Understand the Role of Sodium in Organic Reactions

Sodium, when dissolved in liquid ammonia, is often used in specific organic reactions such as the Birch reduction. In this context, sodium acts in a particular chemical capacity that influences the reaction.

Step 2: Define the Terms

Identify and define the roles of each agent type listed in the options: - Oxidizing Agent: Gains electrons and is reduced in a chemical reaction. - Reducing Agent: Loses electrons and is oxidized in a chemical reaction. - Hydrolyzing Agent: Causes the hydrolysis of a compound. - Precipitating Agent: Causes the formation of a precipitate in a solution.

Step 3: Identify Sodium’s Role

In reactions like the Birch reduction, sodium in liquid ammonia donates electrons to the substrate. This means sodium is giving electrons, which defines it as a particular type of agent. Determine which type based on our definitions.

Step 4: Determine the Correct Role

Since sodium provides electrons, thereby being oxidized itself, it acts as a reducing agent. This matches with the definition of a reducing agent, which is a substance that loses electrons.

Key Concepts

Reducing Agent

In the world of chemistry, a reducing agent plays a vital role. This is a substance that donates electrons to another substance in a chemical reaction, thereby reducing it. When a reducing agent donates electrons, it often undergoes oxidation itself.

For example, during the Birch reduction process, sodium in liquid ammonia is used. Sodium serves as the reducing agent because it provides the necessary electrons to the substrate. Here's how it works:

• The reducing agent loses electrons.
• These electrons are gained by another substance, creating a change in that substance's oxidation state.
• The reducing agent is usually oxidized in turn.

The role of a reducing agent is essential in many organic reactions, as it initiates the transfer of electrons, promoting the overall reaction process.

Birch Reduction

The Birch reduction is an intriguing and significant organic reaction. It specifically involves the reduction of aromatic rings into non-aromatic cyclohexadienes through the use of liquid ammonia and sodium as a reducing agent.

This reaction is notable for its application in modifying aromatic compounds, which has various uses in pharmaceutical and chemical industries. Here’s how the process generally unfolds:

• Sodium is dissolved in liquid ammonia.
• Electrons from sodium are relayed to the aromatic compound.
• The aromatic compound is reduced to the corresponding 1,4-cyclohexadiene.

Due to its unique mechanism, the Birch reduction is a powerful tool in organic synthesis, enabling chemists to create a variety of chemical transformations efficiently.

Sodium in Liquid Ammonia

Sodium, when dissolved in liquid ammonia, creates an exceptional environment for certain chemical reactions, including being an effective reducing medium. Liquid ammonia serves as the solvent, providing a medium that supports electron transfer from sodium, the reducing agent.

Here's why this combination is special:

• Liquid ammonia is a polar solvent that stabilizes the released electrons from sodium.
• It allows for electrons to be more freely shared and transferred in the reaction.
• This medium is particularly useful for reducing complex molecules, especially aromatic compounds.

Thus, the use of sodium in liquid ammonia is not just a specific choice; it is crucial for enabling reductions like the Birch reduction, which involve intricate electron transfers.