Question

Ethyl iodide and n-propyl iodide are allowed to undergo the Wurtz reaction. The alkane which will not be obtained in this reaction is:
(A) Butane
(B) Propane
(C) Pentane
(D) Hexane

Answer 1

Hint: Haloalkanes reacts with sodium in the presence of dry ether to form alkanes is known as the Wurtz reaction. Two same or different alkyl halides can be reacted to form alkanes using the Wurtz reaction. More than one alkane is expected to form as the products in the reaction.

Complete answer:
First, we will understand the Wurtz reaction. We know that in this reaction two same or different alkyl halides are reacted to form alkanes. So here the question says that Ethyl iodide and n-propyl iodide are allowed to undergo the Wurtz reaction. So the reactants of the reactions are Ethyl iodide $ \left( {C{H_3}C{H_2}I} \right) $ and n-propyl iodide $ \left( {C{H_3}C{H_2}C{H_2}I} \right) $ . Now from the reactants, we can observe that they are different alkyl halides, so the products will be formed as self-addition products and cross-addition products. The overall Wurtz reactions are as follows:
 $ C{H_3}C{H_2}I + C{H_3}C{H_2}C{H_2}I\xrightarrow[{Ether}]{{Na}}C{H_3}C{H_2}C{H_2}C{H_3} + C{H_3}C{H_2}C{H_2}C{H_2}C{H_3} + C{H_3}C{H_2}C{H_2}C{H_2}C{H_2}C{H_3} $
So we can observe that when the reactants Ethyl iodide and n-propyl iodide are allowed to undergo the Wurtz reaction the possible alkenes formed are butane, pentane, and hexane. When $ \left( {C{H_3}C{H_2}I} \right) $ undergoes self-addition reaction it forms $ \left( {C{H_3}C{H_2}C{H_3}C{H_3}} \right) $ butane. When $ \left( {C{H_3}C{H_2}C{H_2}I} \right) $ undergoes self-addition reaction it forms $ \left( {C{H_3}C{H_2}C{H_3}C{H_2}C{H_2}C{H_3}} \right) $ hexane. Now when Ethyl iodide and n-propyl iodide are allowed to undergo cross-addition reaction they form another alkane $ \left( {C{H_3}C{H_2}C{H_3}C{H_2}C{H_3}} \right) $ pentane. So, the alkanes formed during the reaction are butane, pentane, and hexane are formed. Propane is the alkane that is not formed in the reaction.
Therefore, the correct option is (B).

Note:
The major product formed in the reaction is pentane formed by the cross-addition reaction of Ethyl iodide and n-propyl iodide. Alkyl halides react with active metals like lithium, sodium, and magnesium. Generally, the Wurtz reaction is used to prepare higher alkanes in chemistry.