Complete the reaction
`underset("But-2-yne")(CH_(3)-C-=C-CH_(3)) underset(H_(2))overset(Na//liq. NH_(3))to ?`

Explanation

To complete the reaction of but-2-yne (CH₃-C≡C-CH₃) with sodium in liquid ammonia, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: We start with but-2-yne, which has the structure CH₃-C≡C-CH₃. This is an alkyne with a triple bond between the second and third carbon atoms.

2. **Understand the Reaction Conditions**: The reaction is carried out using sodium (Na) in the presence of liquid ammonia (NH₃). This combination is known as the Birch reduction.

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