Question

Explain the following reactions with suitable chemical equations:
(i) Wurtz reaction
(ii) Wurtz-Fittig reaction

Hint:

In the Wurtz reaction, two alkyl halides react in the presence of sodium to form a symmetrical alkane. The Wurtz-Fittig reaction involves one alkyl halide and one aryl halide, resulting in an alkyl-aromatic compound.

Answer 1

(i) Wurtz Reaction:
The Wurtz reaction is a coupling reaction in which two alkyl halides react with sodium metal in dry ether to form a higher alkane. This reaction proceeds through the formation of free radicals, and the general reaction is as follows: \[ 2 R - \text{X} + 2 \text{Na} \rightarrow R - R + 2 \text{NaX} \] Where: - \( R - \text{X} \) is an alkyl halide (for example, ethyl chloride \( \text{C}_2\text{H}_5\text{Cl} \)), - \( R - R \) is the resulting alkane (for example, ethane \( \text{C}_2\text{H}_6 \)), - \( \text{NaX} \) is the sodium halide (for example, sodium chloride \( \text{NaCl} \)). In this reaction, sodium (Na) donates electrons to the alkyl halide, generating free radicals. These free radicals combine to form a new alkane. The Wurtz reaction is primarily used to synthesize symmetrical alkanes.
(ii) Wurtz-Fittig Reaction:
The Wurtz-Fittig reaction is a coupling reaction that involves the reaction of an alkyl halide with an aryl halide in the presence of sodium metal, forming a biphenyl derivative or an alkyl-aromatic compound. It is a combination of the Wurtz reaction and the Fittig reaction. The general reaction is: \[ R - \text{X} + C_6H_5 - \text{Y} + \text{Na} \rightarrow R - C_6H_5 + \text{NaXY} \] Where: - \( R - \text{X} \) is an alkyl halide, - \( C_6H_5 - \text{Y} \) is an aryl halide, - \( R - C_6H_5 \) is the resulting alkyl-aromatic compound (for example, toluene, \( \text{C}_7\text{H}_8 \)). This reaction is used to form substituted benzene derivatives. Sodium metal reacts with the halides, resulting in the formation of free radicals that couple to produce the alkyl-aromatic compound.