Question

2-Methylpropane can be prepared by Wurtz reaction. The haloalkanes taken along with metallic sodium and dry ether are:

• A. Chloromethane and 2-chloropropane
• B. Chloroethane and chloromethane
• C. Chloroethane and 1-chloropropane
• D. Chloromethane and 1-chloropropane

Hint:

In the Wurtz reaction, chloromethane and 2-chloropropane react with sodium in dry ether to form 2-methylpropane via alkyl radical coupling.

Answer 1

The Correct Option is A

The question requires us to determine which pair of haloalkanes, when used in the Wurtz reaction with metallic sodium and dry ether, produces 2-methylpropane. The Wurtz reaction involves coupling two alkyl halides in the presence of sodium metal to form a higher alkane.

2-Methylpropane has the molecular formula of \({\text{C}}_4{\text{H}}_{10}\). To achieve this via the Wurtz reaction, the two haloalkanes chosen must form the correct structure upon coupling. Let's analyze the options: 

1. Chloromethane and 2-chloropropane: 
   - Chloromethane \((\text{CH}_3\text{Cl})\) and 2-chloropropane \((\text{C}_3\text{H}_7\text{Cl})\) couple to form 2-methylpropane \((\text{CH}_3-CH(CH_3)_2)\).
2. Chloroethane and chloromethane: 
   - Chloroethane \((\text{C}_2\text{H}_5\text{Cl})\) and chloromethane \((\text{CH}_3\text{Cl})\) will not correctly form 2-methylpropane.
3. Chloroethane and 1-chloropropane: 
   - This option will yield alkanes different from 2-methylpropane.
4. Chloromethane and 1-chloropropane: 
   - Combination of these would form isomers but not specifically 2-methylpropane.

The correct pair is therefore Chloromethane and 2-chloropropane. When these are reacted with sodium in dry ether, they successfully couple to form 2-methylpropane due to the favorable position of the functional groups facilitating this particular isomer formation.

Thus, the correct answer is:

• Chloromethane and 2-chloropropane