Which can yield acetylene in single step

Options

A. Propyne
B. Ethene
C. Ethylene dichloride
D. Sodium acetate

Answer

To determine which compound can yield acetylene in a single step, we need to analyze the given options and the reactions involved. Acetylene (C2H2) can be produced from certain hydrocarbons through dehydrohalogenation or elimination reactions.

### Step-by-Step Solution:

1. **Identify the Compounds**: The options provided are:
- Propyne (C3H4)
- Ethene (C2H4)
- Ethylene dichloride (C2H4Cl2)

2. **Analyze Propyne**:
- Propyne has the structure CH≡C-CH3.
- To form acetylene from propyne, we would need to remove a methyl group, which cannot be done in a single step. Therefore, propyne does not yield acetylene directly.

3. **Analyze Ethene**:
- Ethene has the structure CH2=CH2.
- Ethene cannot be converted to acetylene in a single step either, as it would require additional steps to remove hydrogen atoms or add other reagents.

4. **Analyze Ethylene Dichloride**:
- Ethylene dichloride has the structure CH2Cl-CH2Cl.
- When treated with alcoholic KOH, a strong base, it can undergo dehydrohalogenation. The reaction proceeds as follows:
- The base abstracts a hydrogen atom, and a chlorine atom is eliminated, leading to the formation of vinyl chloride (CH2=CHCl).
- A second dehydrohalogenation occurs, resulting in the formation of acetylene (C2H2):
\[ \text{C2H4Cl2} + 2 \text{KOH (alc)} \rightarrow \text{C2H2} + 2 \text{KCl} + 2 \text{H2O} \]
- This is a single-step reaction that produces acetylene.

5. **Conclusion**:
- Among the given options, ethylene dichloride (C2H4Cl2) can yield acetylene in a single step when treated with alcoholic KOH.

### Final Answer:
**Ethylene dichloride (C2H4Cl2) can yield acetylene in a single step.**