Question

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

Short answer

Sodium in liquid ammonia is used as a reducing agent.

Step-by-step solution

Identify the Reaction Role

First, we need to understand what role sodium in liquid ammonia typically plays in organic reactions. Sodium is generally used to add electrons to a compound, facilitating the reduction of that compound.

Analyze Possible Answers

We need to consider the definitions: an oxidizing agent gains electrons, a reducing agent loses electrons, a hydrolyzing agent breaks compounds with water, and a precipitating agent causes a substance to form a solid out of a solution.

Match Definitions with Roles

Since sodium in liquid ammonia is involved in adding electrons and reducing a compound by donating electrons, sodium acts as a 'reducing agent.' This matches with option (b).

Confirm the Answer

Sodium in liquid ammonia donates electrons, which is the defining characteristic of a reducing agent, confirming that the appropriate answer is (b) reducing agent.

Key concepts

Reducing Agents in Organic Chemistry

Reducing agents are substances that donate electrons to another compound, thereby reducing it. This process causes the reducing agent itself to become oxidized. In organic chemistry, reducing agents are pivotal for transforming certain types of functional groups into others by altering their oxidation states.

Some common functional group conversions carried out by reducing agents include:

• Alkenes to alkanes through the addition of hydrogen atoms.
• Aldehydes and ketones to alcohols by increasing hydrogen atom count or electron density.
• Carboxylic acids to primary alcohols, using stronger reducing agents.

Reducing agents come in various forms, including molecular H₂ gas, metals such as sodium, and complex organometallic reagents like lithium aluminum hydride (LiAlH₄). Each of these has specific applications depending on the type of organic compound being reduced and the desired product.

Understanding the roles and mechanisms of reducing agents is essential for predicting and controlling outcomes in organic synthesis.

The Role of Sodium in Liquid Ammonia

Sodium in liquid ammonia is a classic reducing agent, utilized primarily due to its ability to deliver electrons effectively to various organic substrates. When sodium dissolves in liquid ammonia, it forms solvated electrons, which are free and highly reactive. These solvated electrons play a crucial role in making sodium in liquid ammonia such an effective reducing agent.

Some of the noteworthy uses of sodium in liquid ammonia include:

• Reducing aromatic double bonds, a reaction that can help modify aromatic compounds by adding electrons to the system.
• Simplifying alkyne reductions, transforming them into trans-alkenes due to the electron transfer process.

The use of sodium in liquid ammonia enables selective reductions, thanks to its ability to deliver electrons gently, making it suitable for sensitive substrates that might decompose under harsh conditions. The interplay of sodium and liquid ammonia in transferring these electrons forms the heart of many key organic transformations.

Electron Transfer in Organic Chemistry

Electron transfer is a fundamental concept in organic chemistry, underpinning various redox reactions where electrons are transferred between chemical species. This transfer is key to altering the chemical structure and properties of organic molecules.

Electron transfer reactions often involve reducing agents, such as sodium in liquid ammonia, where the reducing agent donates electrons to another molecule, facilitating the reduction process. Through electron transfer, bonds can form or break, leading to intricate molecular rearrangements. Here’s how electron transfer plays a role:

• Initiating radical reactions by breaking bonds and forming new radical species.
• Facilitating the conversion of functional groups in synthetic transformations.
• Driving the reduction of unsaturated compounds such as alkenes and alkynes.

Mastering the concept of electron transfer allows chemists to manipulate organic reactions precisely, leading to desired compounds and understanding mechanisms at a fundamental level. This knowledge is crucial in developing new synthetic pathways and improving existing organic reactions.