Question

Of $ 2 - bromo - 3 - methylbutane,\;2 - chlorobutane,\;2 - chloro - 2 - methylpropane $ which haloalkanes will give $ 3,4 - dimethylhexane $ when treated with sodium metal (Wurtz reaction)? Write the reaction equation?

Answer 1

Hint: Wurtz reaction is one of the important reactions in organic chemistry. It is the reaction between two molecules of alkyl halides that reacts with two molecules of sodium metal to form one molecule of higher alkane consisting of all the carbon atoms in both the molecules of alkyl halide.

Complete Step By Step Answer:
Given molecules are $ 2 - bromo - 3 - methylbutane,\;2 - chlorobutane,\;2 - chloro - 2 - methylpropane $
The product that has to be formed by Wurtz reaction is $ 3,4 -$ dimethylhexane which has eight carbon atoms. Out of these eight carbons, six carbons are in base or parent carbon chain and the remaining two carbons are inside chain as in the product it is mentioned as hexane.
Thus, the alkyl halides must have four carbons, in which at the $ {2^{nd}} $ position the halogen atom like bromine must be present, as in this case only the $ {1^{st}} $ carbon will go to the substitution in the product by forming the desired product.
Let us see the chemical reaction that involves the two molecules of $ 2 - chlorobu\tan e $ with sodium metal to form $ 3,4 -$ dimethylhexane
 $ 2C{H_3}C{H_2}CH\left( {Br} \right)C{H_3} + 2Na \to C{H_3}C{H_2}CH\left( {C{H_3}} \right)CH\left( {C{H_3}} \right)C{H_2}C{H_3} $
In the above reaction, the product is $ 3,4 -$ dimethylhexane which was formed from two molecules of $ 2 -$ chlorobutane reacts with sodium metal and the reaction can be termed as Wurtz reaction.
Thus, of $ 2 - bromo - 3 - methylbutane,2 - chlorobutane,2 - chloro - 2 - methylpropane $ , $ 2 - chlorobutane $ will give $ 3,4 - dimethylhexane $ when treated with sodium metal.

Note:
Wurtz reaction can be mostly used for the preparation of symmetrical alkanes. Mainly, the preparation of higher membered alkanes by using sodium metal. But the sodium metal vigorously reacts with water in the atmosphere also. Hence precautions must be taken while dealing with sodium metal.