Which alkyl chloride would yield following pure alkene on reaction with alcoholic KOH ?
`(i)CH_3-oversetoverset(CH_3)(|)C=CH_2 " " (ii)CH_3-CH_2-CH_2-CH=CH_2 " " (iii)CH_3-CH_2-undersetunderset(CH_3)(|)C=CH_3`

Answer

To determine which alkyl chloride would yield the specified pure alkenes when reacted with alcoholic KOH, we need to analyze each alkene and deduce the corresponding alkyl chloride.

### Step-by-Step Solution:

1. **Identify the Alkenes**:
- (i) \( CH_3-C(CH_3)=CH_2 \) (Alkene with a branched structure)
- (ii) \( CH_3-CH_2-CH_2-CH=CH_2 \) (Linear alkene)
- (iii) \( CH_3-CH_2-C(CH_3)=CH_3 \) (Alkene with a branched structure)

2. **Understanding the Reaction**:
- The reaction with alcoholic KOH involves a dehydrohalogenation process where a hydrogen atom and a halogen (Cl in this case) are removed from adjacent carbon atoms (beta elimination).
- The alkyl chloride must have a leaving group (Cl) on the carbon adjacent to the carbon that will form the double bond.

3. **Analyzing Each Alkene**:
- **For Alkene (i)**:
- The structure suggests that the alkyl chloride must have a tertiary carbon (due to the branching) where Cl is attached.
- Possible alkyl chloride: \( CH_3-C(CH_3)-CH_2-Cl \) (Tertiary carbon with Cl).

- **For Alkene (ii)**:
- This is a linear alkene, suggesting that the alkyl chloride should have a primary or secondary carbon with Cl.
- Possible alkyl chloride: \( CH_3-CH_2-CH_2-CH_2-Cl \) (Primary carbon with Cl).

- **For Alkene (iii)**:
- This structure indicates a branched alkene, so the alkyl chloride must also have a tertiary carbon with Cl.
- Possible alkyl chloride: \( CH_3-CH_2-C(CH_3)-CH_2-Cl \) (Tertiary carbon with Cl).

4. **Conclusion**:
- For each alkene, we can summarize the corresponding alkyl chlorides:
- (i) \( CH_3-C(CH_3)-CH_2-Cl \)
- (ii) \( CH_3-CH_2-CH_2-CH_2-Cl \)
- (iii) \( CH_3-CH_2-C(CH_3)-CH_2-Cl \)

### Final Answers:
- (i) Alkyl chloride: \( CH_3-C(CH_3)-CH_2-Cl \)
- (ii) Alkyl chloride: \( CH_3-CH_2-CH_2-CH_2-Cl \)
- (iii) Alkyl chloride: \( CH_3-CH_2-C(CH_3)-CH_2-Cl \)