`CH_(3)-CH_(2)-C -=CH overset( R)underset(H_(3)O^(oplus))to` Butanone, R is

Options

A. `Hg^(+2)`
B. `KMnO_(4)`
C. `KClO_(3)`
D. `K_(2)Cr_(2)O_(7)`

Answer

To solve the question, we need to determine the reagent \( R \) that allows the conversion of the alkyne \( CH_3-CH_2-C \equiv CH \) into butanone in the presence of \( H_3O^+ \).

### Step-by-Step Solution:

1. **Identify the Reactant**: The given reactant is \( CH_3-CH_2-C \equiv CH \), which is 1-butyne, an alkyne with four carbon atoms.

2. **Understand the Reaction Type**: The conversion of an alkyne to a ketone typically involves a reaction known as oxymercuration followed by demercuration. This process is used to convert alkynes into carbonyl compounds (ketones or aldehydes).

3. **Identify the Reagent \( R \)**: In the oxymercuration reaction, a mercuric salt, specifically \( Hg^{2+} \) (mercuric ion), is used. Therefore, \( R \) is \( Hg^{2+} \).

4. **Reaction Mechanism**:
- The mercuric ion adds to the triple bond of the alkyne, forming a mercurial intermediate.
- The addition follows Markovnikov's rule, where the mercuric ion adds to the less substituted carbon of the alkyne.
- The intermediate then undergoes hydrolysis in the presence of \( H_3O^+ \), leading to the formation of an enol.

5. **Tautomerization**: The enol formed from the hydrolysis will tautomerize to form the corresponding ketone. In this case, the enol will convert to butanone \( CH_3-CH_2-C(=O)-CH_3 \).

6. **Final Product**: The final product of the reaction is butanone.

### Conclusion:
Thus, the reagent \( R \) that facilitates this conversion is \( Hg^{2+} \).