Question

A mixture of 1-iodoethane and 1-iodopropane is treated with sodium metal and dry ether to carry out Wurtz reaction. Which of the following hydrocarbons will be formed?
(A) Propane + Hexane
(B) Ethane + Propane
(C) Butane + Propane
(D) Butane + Pentane + Hexane

Answer 1

Hint: Read about the Wurtz reaction. Think about the products formed using one kind of reactant and the kinds of products formed from using mixed reactants. Write the chemical reaction which takes place when 1-iodoethane and 1-iodopropane react with sodium metal in the presence of dry ether to get the answer.

Complete step by step solution:
-Wurtz reaction is an organic reaction in which two moles of alkyl halides react with sodium metal to form one mole of an alkane having double the number of carbon atoms.
-For example, two moles of methyl chloride reacts with sodium metal in the presence of dry ether to form one mole of ethane.
\[2C{{H}_{3}}Cl+2Na\xrightarrow{dry\,ether}C{{H}_{3}}-C{{H}_{3}}+2NaCl\]
-There are two types of Wurtz reactions, simple and mixed. Simple Wurtz reaction is explained above and yields alkane having an even number of carbon atoms. In a mixed Wurtz reaction, different alkyl halides are used and instead of one product, multiple products are formed.
-For example, 1-iodoethane and 1-iodopropane react with sodium metal in the presence of dry ether to form n-pentane. But since this reaction is an example of a mixed Wurtz reaction, two more types of products will be formed.
-1-iodoethane will get combined to form n-butane and similarly, 1-iodopropane will get combined to form n-hexane.
\[\begin{align}
3C{{H}_{3}}C{{H}_{2}}I+3C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}I+2Na\xrightarrow{dry\,ether}C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}+C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}} & \\
+C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{3}}+2NaI & \\
\end{align}\]
-Therefore, when a mixture of 1-iodoethane and 1-iodopropane is treated with sodium metal and dry ether to carry out Wurtz reaction, products obtained are butane, pentane and hexane.

Therefore, answer is option (D).

Note: Remember, in simple Wurtz reaction, hydrocarbon chains in the same alkyl halide molecules will combine to form only one type of product due to the presence of only one type of alkyl halide. In a mixed Wurtz reaction, hydrocarbon chains from different alkyl halide molecules combine to form mixed alkane and the reactants will also combine with the same molecules to form simple alkanes as well. So, in a mixed Wurtz reaction, multiple products are obtained but in a simple Wurtz reaction, only one product is obtained.