The reagent used for getting trans alkene from alkyl substituted acetylene with hydrogen is

Options

A. Na in liq. `NH_(3)`
B. Li in liq. `NH_(3)`
C. Both (1) and (2)
D. `H_(2)//Ni` (or) Pt (or) Pd

Answer

To solve the question regarding the reagent used for obtaining trans-alkene from alkyl substituted acetylene with hydrogen, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of Alkyl Substituted Acetylene**:
- Alkyl substituted acetylene can be represented as CH3C≡CCH3 (2-butyne). This compound has a triple bond between the two carbon atoms.

2. **Understand the Reaction Conditions**:
- The question asks for the reagent that can convert this alkyl substituted acetylene into a trans-alkene. The reagents mentioned are sodium in liquid ammonia and lithium in liquid ammonia.

3. **Reaction with Sodium or Lithium in Liquid Ammonia**:
- When alkyl substituted acetylene (like 2-butyne) reacts with sodium in liquid ammonia, it undergoes a reduction process. This involves the formation of a radical anion intermediate.
- The reaction proceeds through the formation of a double bond (alkene) with the trans configuration due to the specific mechanism of the reaction.

4. **Formation of Trans-Alkene**:
- The process involves the transfer of electrons from sodium to the acetylene, resulting in the formation of a trans-alkene (in this case, trans-2-butene).
- Similarly, lithium in liquid ammonia can also facilitate this reaction, leading to the same product.

5. **Conclusion**:
- Both sodium in liquid ammonia and lithium in liquid ammonia can be used to convert alkyl substituted acetylenes into trans-alkenes. Therefore, the correct answer is that both reagents (sodium and lithium in liquid ammonia) are suitable for this transformation.

### Final Answer:
The reagents used for getting trans-alkene from alkyl substituted acetylene with hydrogen are sodium in liquid ammonia and lithium in liquid ammonia (both 1 and 2).

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