The major product formed in the following reaction is
The Correct Option is B
Approach Solution - 1
The Birch reduction is a process in which alkynes react with alkali metals (such as sodium, Na) in liquid ammonia (NH3) to produce trans-alkenes.
This reduction specifically targets internal alkynes, causing them to form trans-alkenes. Terminal alkynes, however, do not undergo this reduction and remain unaffected by the reaction.
Step 2: The Reaction Mechanism
When an alkyne undergoes Birch reduction, the alkali metal (sodium) donates electrons to the alkyne, resulting in the formation of a radical anion. This species reacts with ammonia to form a trans-alkene.
This reduction is selective and works primarily for internal alkynes, converting them to trans-alkenes. Terminal alkynes do not participate in this reaction and remain unchanged.
Step 3: Key Feature of the Reaction
The key characteristic of Birch reduction is the formation of **trans-alkenes** from internal alkynes. This transformation does not occur with terminal alkynes, making them unreactive under these conditions.
Step 4: Conclusion
Option (B) correctly describes this characteristic behavior of alkynes under Birch reduction conditions. It specifies that alkynes undergo Birch reduction in liquid ammonia to form trans-alkenes, while terminal alkynes do not undergo this reduction.
It is a case of Birch reduction. Alkynes on reaction with alkali metal in liq. NH3 gives trans-alkene. But terminal alkynes do not get reduced.
The correct answer is option (B):
Approach Solution -2
Option (B) states that alkynes undergo Birch reduction in liquid ammonia to form trans-alkenes, but terminal alkynes do not undergo this reduction. This succinctly summarizes the process known as Birch reduction, where alkynes react with alkali metals in liquid ammonia to produce trans-alkenes, except for terminal alkynes, which remain unaffected by this reaction. Therefore, option (B) accurately describes the characteristic behavior of alkynes under Birch reduction conditions.
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Concepts Used:
Introduction to Organic Chemistry
Organic chemistry is the branch of chemistry that involves the scientific study of organic compounds. Organic chemistry primarily deals with the structure and chemical composition of organic compounds, the physical and chemical properties of organic compounds, and the chemical reactions undergone by these compounds.
Reaction Intermediates in Organic Chemistry:
Intermediates can be understood as the first product of a consecutive reaction. For example, in a chemical reaction, if A→B and B→C, then, B can be said to be the intermediate for reaction A→C. The reactions in organic chemistry occur via the formation of these intermediates.
Reagents in Organic Chemistry:
Reagents are the chemicals that we add to bring about a specific change to an organic molecule. Any general reaction in organic chemistry can be written as:
Substrate + Reagent → Product
Where the substrate is an organic molecule to which we add the reagent. Based on the ability to either donate or abstract electrons, the reagents can be classified as:
- Electrophiles
- Nucleophiles