Reduction of 2 - butyne with sodium in liquid ammonia gives predominantly

Options

A. cis - 2- butene
B. n - butane
C. trans - 2- butene
D. None of these

Answer

To solve the problem of what product is obtained from the reduction of 2-butyne with sodium in liquid ammonia, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**: The reactant given is 2-butyne, which has the structure:
\[ \text{CH}_3-\text{C} \equiv \text{C}-\text{CH}_3 \]
This indicates a triple bond between the second and third carbon atoms in a four-carbon chain.

2. **Understand the Reaction Conditions**: The reaction involves sodium (Na) in liquid ammonia (NH₃). This condition is known as Birch reduction, which is specifically used to reduce alkynes to alkenes.

3. **Determine the Type of Alkene Formed**: The Birch reduction typically yields trans alkenes when reducing alkynes. This is a key aspect of the reaction conditions, as the presence of sodium in liquid ammonia favors the formation of the trans isomer.

4. **Draw the Product**: When 2-butyne is reduced under these conditions, it will convert to trans-2-butene. The structure of trans-2-butene is:
\[ \text{CH}_3-\text{CH}=\text{CH}-\text{CH}_3 \]
where the two methyl (CH₃) groups are on opposite sides of the double bond.

5. **Conclusion**: Therefore, the predominant product of the reduction of 2-butyne with sodium in liquid ammonia is trans-2-butene.

### Final Answer:
The predominant product is **trans-2-butene**.

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