Question

Which of the following alkane is not formed in Wurtz reaction?
(A) Methane
(B) Ethane
(C) Propane
(D) Butane

Answer 1

Hint: Wurtz reaction is one of the reaction which produces simple higher alkane of the two equivalents derived from alkyl halide in presence of dry ether is a coupling reaction which produces alkane with an increased carbon along with sodium salt of alkyl halide. So only the alkanes with minimum required carbons can be formed from Wurtz reaction.

Complete Solution :
-We know that Wurtz reaction is a kind of reaction in which there is a simple higher alkanes product of the alkyl halides.
-Coming to the question methane contains only one carbon
-Minimum two carbon atoms chains should be present to form alkane by Wurtz reaction process. So methane cannot be formed from the Wurtz reaction.
-So option A is correct
-Ethane has two carbon atom chains so it can be prepared by Wurtz reaction. Therefore this option is incorrect.
-Propane has three carbon atom chains so it can be prepared by Wurtz reaction. Therefore this option is incorrect.
-Similarly, butane has four carbon atom chains so it can be prepared by Wurtz reaction. Therefore this option is incorrect.
-Hence methane having one carbon atom chain so it cannot be prepared by Wurtz reaction.
So, the correct answer is “Option A”.

Note: Wurtz reaction is preferred for the preparation of alkanes with even number of carbon atoms. It is not used for the preparation of alkanes with an odd number of carbon atoms due to the formation of side products. Also, unsymmetrical alkanes can- not be prepared due to the formation of a mixture of species and also alkene is formed due to free radical mechanism.