A hydrocarbon that reacts with sodium in liquid `NH_3` is

Options

A. `CH_3 - CH_2 - C -= C - H`
B. `CH_3 - C-= C - CH_3`
C. `CH_3 - CH= CH - CH_3`
D. `CH_3 - CH_2 - CH = CH_2`

Answer

To determine which hydrocarbon reacts with sodium in liquid ammonia (NH₃), we need to understand the nature of the hydrocarbons and the reaction conditions.

### Step-by-Step Solution:

1. **Identify the Type of Hydrocarbons**:
- Hydrocarbons can be classified into alkanes, alkenes, and alkynes.
- Alkenes have double bonds, while alkynes have triple bonds.

2. **Understand the Reactivity with Sodium in Liquid NH₃**:
- Sodium in liquid ammonia acts as a strong base.
- It can deprotonate acidic hydrogens from certain hydrocarbons.

3. **Identify Acidic Hydrogens**:
- Terminal alkynes (alkynes with a hydrogen atom attached to the carbon involved in the triple bond) have acidic hydrogens.
- The hydrogen attached to the sp-hybridized carbon of terminal alkynes is more acidic compared to those in alkenes or alkanes.

4. **Reaction Mechanism**:
- When a terminal alkyne reacts with sodium in liquid ammonia, sodium will remove the acidic hydrogen, forming a sodium salt of the alkyne and releasing hydrogen gas (H₂).
- For example, if we consider a terminal alkyne like ethyne (C₂H₂), the reaction would yield sodium acetylide (C₂H₃Na) and hydrogen gas.

5. **Conclusion**:
- Among hydrocarbons, only terminal alkynes can react with sodium in liquid ammonia due to the presence of acidic hydrogen.

### Final Answer:
The hydrocarbon that reacts with sodium in liquid NH₃ is a **terminal alkyne**.

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