Acetylene on passing through excess of `HOCl` solution forms

Options

A. ethylene chlorohydrin
B. glyoxal
C. ethylene glycol
D. dichloroacetaldehyde

Explanation

To solve the question of what acetylene forms when passed through excess HOCl solution, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- Acetylene (C₂H₂) has the structure H-C≡C-H.
- HOCl (hypochlorous acid) can dissociate into H⁺ and OCl⁻.

2. **Reaction Mechanism**:
- When acetylene reacts with HOCl, the triple bond between the carbon atoms can react with the OCl⁻ ion.
- The OCl⁻ will add to one of the carbon atoms, while the H⁺ from HOCl will add to the other carbon.

3. **Formation of Intermediates**:
- The reaction leads to the formation of a vinyl chloride intermediate (C₂HClO), where one carbon has a chlorine atom and the other has a hydroxyl group (OH).

4. **Tautomerization**:
- The intermediate can undergo tautomerization, where the hydrogen atom shifts, leading to the formation of a carbonyl group (C=O).
- This results in the formation of an aldehyde.

5. **Final Product**:
- The final product after the reaction with excess HOCl will be dichloroacetaldehyde (CCl₂CHO), where the carbonyl carbon is bonded to two chlorine atoms and one hydroxyl group.

### Conclusion:
The product formed when acetylene is passed through excess HOCl solution is **Dichloroacetaldehyde**.

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