Methane cannot be prepared by

Options

A. Corey-house synthesis
B. Wurtz reaction
C. Fittig reaction
D. All of these

Answer

To determine how methane cannot be prepared, we will analyze three different methods of synthesis and explain why each method fails to produce methane (CH₄).

### Step-by-Step Solution:

1. **Coriolis Synthesis**:
- In this method, we start with dialkylcuprate (R₂CuLi) and an alkyl halide (R'X).
- The reaction involves the transfer of alkyl groups, resulting in the formation of an alkane.
- The minimum number of carbon atoms in the product is two because two alkyl groups (R and R') are involved.
- Since methane has only one carbon atom, this method cannot produce methane.

2. **Wurtz Reaction**:
- The Wurtz reaction involves the reaction of alkyl halides with sodium in dry ether.
- This reaction generates radicals (R•) from the alkyl halides, which then couple to form alkanes.
- Similar to the previous method, at least two alkyl groups are required to form the product, leading to a minimum of two carbon atoms.
- Therefore, methane cannot be produced through this method either.

3. **Fittig Reaction**:
- The Fittig reaction uses aryl halides and sodium in dry ether, leading to the formation of biphenyls from aryl radicals.
- This reaction also results in the coupling of aryl radicals, which cannot yield methane since it involves only aryl groups.
- As with the previous methods, the minimum number of carbon atoms in the product is two, thus excluding the possibility of forming methane.

### Conclusion:
Based on the analysis of the three methods, we conclude that methane cannot be prepared by any of the discussed methods (Coriolis synthesis, Wurtz reaction, or Fittig reaction). Therefore, the answer is that methane cannot be prepared by these methods.