Question

On treating the mixture of two alkyl halides with sodium metal in dry ether, \[2 - {\rm{methylpropane}}\]was obtained. The alkyl halides are:
A. \[2 - {\rm{chloropropane}}\]and chloromethane
B. \[2 - {\rm{chloropropane}}\]and chloroethane
C. chloromethane and chloroethane
D. chloromethane and \[1 - {\rm{chloropropane}}\]

Answer 1

Hint: Wurtz reaction involves the interaction of two molecules of alkyl halides and sodium metal in presence of dry ether. Alkyl halides are also known as a mono alkanes.

Complete Step by Step Solution:
Many of the substitution reactions which do occur when organometallic reagents are used as nucleophiles proceed with only moderate yields. The coupling of haloalkanes in the presence of an active metal is known as the Wurtz reaction. The reaction is usually accomplished by adding sodium metal to an organohalogen compound in an inert solvent. The organosodium compound which forms combines with an unreacted haloalkane.
The general equation of Wurtz reaction is as shown below:

where, \[{\rm{R}}\]= alkyl group
\[{\rm{X}}\]= halogen atom
When 2-chloropropane and chloromethane is used, the product obtained is 2-methylpropane and sodium chloride. Hence, option (A) is correct. The reaction is as shown below:

Image: reaction of 2-chloropropane and chloromethane in presence of dry ether.
Hence, the two alkyl halides are 2-chloropropane and chloromethane.
Therefore, option A is correct.
Additional information: Methane cannot be prepared by this method. When a mixture of two different alkyl halides is used, a mixture of three alkanes is formed. It is difficult to separate such mixtures into individual alkanes. Thus, the method is suitable for the synthesis of symmetrical alkanes from two molecules of the same alkyl halide. It cannot be used for the preparation of unsymmetrical alkanes from a mixture of two different alkyl halides because it produces a mixture of alkanes.

Note: Wurtz reaction was effectively applied to the synthesis of a small ring-sized hydrocarbon to give an unusually high yield of the product. A mixture of three alkenes is obtained when different alkyl halides are used.