Question

The following compound which cannot be prepared by Wurtz reaction is

• A. Methane
• B. Ethane
• C. Butane
• D. Propane

Hint:

Wurtz reaction typically gives alkanes with an even number of carbon atoms when a single alkyl halide is used. Methane (C1) is impossible to obtain.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Wurtz reaction involves the coupling of two alkyl halides with sodium metal to give a higher alkane. It is generally used to prepare symmetrical alkanes with an even number of carbon atoms.

Step 2: Detailed Explanation:
The general reaction is: 2R-X + 2Na \(\rightarrow\) R-R + 2NaX. • (A) Methane (CH\(_4\)): To prepare methane, one would need a methyl halide (CH\(_3\)X) to couple. 2CH\(_3\)X + 2Na \(\rightarrow\) C\(_2\)H\(_6\) (ethane), not methane. Wurtz reaction always yields a product with an even number of carbon atoms if a single alkyl halide is used. Methane has one carbon and cannot be prepared this way. • (B) Ethane: Can be prepared from methyl halide. • (C) Butane: Can be prepared from ethyl halide. • (D) Propane: Has an odd number of carbons. It can be prepared by a mixed Wurtz reaction using methyl and ethyl halides, but yields a mixture. However, it is possible, while methane is impossible.

Step 3: Final Answer:
Methane cannot be prepared by Wurtz reaction, which corresponds to option (A).