Propyne reacts with `Br_(2)//HOH` to produce

Options

A. 1,1,2,2-Tetrabromopropane
B. Acetone
C. Acetaldehyde
D. `alpha` - Bromoacetone

Answer

To solve the problem of what product is formed when propyne reacts with bromine and water, we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are propyne (C₃H₄) and a mixture of bromine (Br₂) and water (H₂O).

### Step 2: Understand the Reaction Type
The reaction involves bromination in the presence of water. This means that bromine will add across the triple bond of propyne, and water will also participate in the reaction.

### Step 3: Mechanism of the Reaction
1. **Electrophilic Addition**: The triple bond in propyne acts as a nucleophile and attacks the bromine molecule (Br₂), leading to the formation of a bromonium ion intermediate.
2. **Nucleophilic Attack by Water**: Water (H₂O) then attacks the more substituted carbon of the bromonium ion, leading to the formation of a bromoalcohol.
3. **Deprotonation**: The bromoalcohol can undergo deprotonation to yield an enol.

### Step 4: Identify the Final Product
In this case, the product formed is alpha-bromoacetone. The structure of alpha-bromoacetone (C₃H₅BrO) can be represented as follows:
- The bromine (Br) is added to one carbon, and the hydroxyl group (OH) from water is added to the adjacent carbon.

### Conclusion
The final product of the reaction between propyne and bromine in the presence of water is **alpha-bromoacetone**.