Which of the following pathways produces 2-hexanone?
(i) 1-Hexyne is treated with `Hg^(2oplus) //"dil " H_(2)SO_(4)`
(ii) 3-methylhept-2-ene is treated with `O_(3)` followed by hydrolysis.
(iii) n-butyl magnesium bromide reacts with acetaldehyde followed by hydrolysis and then oxidation with chromic acid.
(iv) Hydroboratioin-oxidation of 1-hexyne.

Options

A. (i), (ii) and (iii)
B. (i) and (ii) only
C. (i), (ii) and (iv)
D. (i) amd (iii) only

Answer

To determine which of the given pathways produces 2-hexanone, we will analyze each option step by step.

### Step 1: Analyze Option (i)
1. **Starting Material**: 1-Hexyne (C6H10)
2. **Reagents**: `Hg^(2+)` and `dil H2SO4`
3. **Reaction**: This is a hydration reaction where 1-heptyne will undergo Markovnikov addition of water.
- The reaction will add an -OH group to the more substituted carbon and an -H to the less substituted carbon.
- The product will be 2-hexanol (C6H14O).
4. **Tautomerization**: 2-hexanol can tautomerize to form 2-hexanone (C6H12O).

**Conclusion**: This pathway produces 2-hexanone.

### Step 2: Analyze Option (ii)
1. **Starting Material**: 3-methylhept-2-ene (C8H16)
2. **Reagents**: `O3` followed by hydrolysis.
3. **Reaction**: Ozonolysis will cleave the double bond.
- The structure of 3-methylhept-2-ene is:
```
CH3-CH(CH3)-C=C-CH2-CH2-CH3
```
- Ozonolysis will break the double bond and form two carbonyl compounds.
4. **Products**: The ozonolysis of 3-methylhept-2-ene will yield two products, one of which is 2-hexanone.

**Conclusion**: This pathway also produces 2-hexanone.

### Step 3: Analyze Option (iii)
1. **Starting Material**: n-butyl magnesium bromide (C4H9MgBr) and acetaldehyde (C2H4O).
2. **Reaction**: The Grignard reagent will attack the carbonyl carbon of acetaldehyde.
- This will form a tertiary alcohol after hydrolysis.
3. **Hydrolysis**: The product after hydrolysis will be a secondary alcohol (C6H14O).
4. **Oxidation**: Upon oxidation with chromic acid, the secondary alcohol will convert to a ketone, specifically 2-hexanone.

**Conclusion**: This pathway produces 2-hexanone.

### Step 4: Analyze Option (iv)
1. **Starting Material**: 1-Hexyne (C6H10)
2. **Reagents**: Hydroboration-oxidation.
3. **Reaction**: Hydroboration-oxidation of 1-heptyne will lead to the addition of -OH to the less substituted carbon.
- The product will be 1-hexanol (C6H14O).
4. **Tautomerization**: 1-hexanol does not tautomerize to form 2-hexanone.

**Conclusion**: This pathway does not produce 2-hexanone.

### Final Answer
The pathways that produce 2-hexanone are:
- (i) 1-Hexyne treated with `Hg^(2+)` and `dil H2SO4`
- (ii) 3-methylhept-2-ene treated with `O3` followed by hydrolysis
- (iii) n-butyl magnesium bromide reacts with acetaldehyde followed by hydrolysis and then oxidation with chromic acid.

Therefore, the correct options are (i), (ii), and (iii).