`CH_3-CH_2-C -= CH underset(H_2O)overset(R)to` Butanone, R is

Options

A. `Hg^("++")`
B. `KMnO_4`
C. `KClO_3`
D. `K_2Cr_2O_7`

Explanation

To solve the question regarding the transformation of the compound `CH3-CH2-C≡CH` (1-butyne) to butanone, we will follow a step-by-step approach.

### Step-by-Step Solution:

1. **Identify the Starting Material**:
The starting material is 1-butyne, which has the structure `CH3-CH2-C≡CH`.

2. **Understand the Target Product**:
The target product is butanone, which has the structure `CH3-CO-CH2-CH3`. Butanone is a ketone, specifically a methyl ketone.

3. **Determine the Reaction Type**:
To convert an alkyne (1-butyne) to a ketone (butanone), we can use a hydration reaction. This typically involves the addition of water (H2O) across the triple bond of the alkyne.

4. **Use of Reagents**:
The hydration of alkynes can be achieved using a reagent such as dilute sulfuric acid (H2SO4) and mercury(II) sulfate (HgSO4) as a catalyst. This process is known as the "Markovnikov addition" where water adds across the triple bond.

5. **Reaction Mechanism**:
- The alkyne undergoes protonation to form a carbocation.
- The carbocation then reacts with water to form an enol.
- The enol tautomerizes to form the ketone (butanone).

6. **Final Reaction**:
The overall reaction can be summarized as:
\[ CH3-CH2-C≡CH + H2O \xrightarrow{H2SO4, HgSO4} CH3-CO-CH2-CH3 \]
This shows that 1-butyne reacts with water in the presence of acid to yield butanone.

### Conclusion:
The reagent R in the reaction is dilute sulfuric acid (H2SO4) along with mercury(II) sulfate (HgSO4) for the hydration of the alkyne to form butanone.