Which gives ketonic group after hydroboration oxidation :

Options

A. `CH_(3)-CH_(2)-C-=CH`
B.
C. `C Cl_(3)-C-=CH`
D. `CH_(3)-underset(CH_(3))underset(|)(CH)-C-=CH`

Answer

To determine which compound gives a ketonic group after hydroboration-oxidation, we will analyze each option step by step.

### Step 1: Understand Hydroboration-Oxidation
Hydroboration-oxidation is a two-step reaction:
1. **Hydroboration**: A boron hydride (BH3) adds across a double or triple bond. The boron atom attaches to the less substituted carbon atom, while hydrogen attaches to the more substituted carbon atom.
2. **Oxidation**: The boron is replaced by a hydroxyl group (OH) using hydrogen peroxide (H2O2) in a basic medium.

### Step 2: Analyze Each Compound

#### Option 1: CH3CH2C≡CH
1. **Hydroboration**:
- BH2 adds to the terminal carbon (less substituted), and H adds to the adjacent carbon.
- Resulting structure: CH3CH2C=CH2 (double bond formed).

2. **Oxidation**:
- Replace BH2 with OH.
- Resulting structure: CH3CH2CH2CHO (an aldehyde).

3. **Conclusion**: This option does not yield a ketone.

#### Option 2: C6H5C≡CH
1. **Hydroboration**:
- BH2 adds to the carbon with the triple bond that is less substituted (the one attached to the phenyl ring), and H adds to the other carbon.
- Resulting structure: C6H5C=CH2.

2. **Oxidation**:
- Replace BH2 with OH.
- Resulting structure: C6H5C(OH)=CH2 (enol form).

3. **Tautomerization**:
- Converts to C6H5C=O (an aldehyde).

4. **Conclusion**: This option does not yield a ketone.

#### Option 3: CCl3C≡CH
1. **Hydroboration**:
- Due to the electron-withdrawing effect of Cl, BH2 adds to the carbon with the triple bond that has a partial negative charge.
- Resulting structure: CCl3C=CH2.

2. **Oxidation**:
- Replace BH2 with OH.
- Resulting structure: CCl3C(OH)=CH2 (enol form).

3. **Tautomerization**:
- Converts to CCl3C=O (a ketone).

4. **Conclusion**: This option yields a ketone.

#### Option 4: CH3C≡CCH3
1. **Hydroboration**:
- BH2 adds to the terminal carbon (less substituted), and H adds to the adjacent carbon.
- Resulting structure: CH3C=CH2.

2. **Oxidation**:
- Replace BH2 with OH.
- Resulting structure: CH3C(OH)=CH2 (enol form).

3. **Tautomerization**:
- Converts to CH3C=O (an aldehyde).

4. **Conclusion**: This option does not yield a ketone.

### Final Answer
After analyzing all options, **Option 3 (CCl3C≡CH)** is the only compound that yields a ketone after hydroboration-oxidation.