Question

Write the major product in the following reactions: (1) Chlorobenzene + Na/dry ether

Hint:

Aryl halide + Na (dry ether) → Fittig reaction → biaryl formation (e.g., biphenyl).

Answer 1

This reaction is known as the Fittig reaction, which is a classic example of the coupling of aryl halides in the presence of sodium metal. In this reaction, two molecules of an aryl halide (such as chlorobenzene) react with sodium to form a biphenyl compound. This type of reaction is widely used to couple aromatic rings, and it is important in the synthesis of various biaryl compounds.
Step 1: Reaction Overview.
The Fittig reaction involves two molecules of an aryl halide, which are typically chlorides, reacting with sodium metal. The sodium atoms donate electrons to the halide molecules, resulting in the formation of free radicals or carbanions. These intermediates then couple to form the biaryl compound. The chemical equation for the reaction is: \[ 2C_6H_5Cl + 2Na \rightarrow C_6H_5{-}C_6H_5 + 2NaCl \]
Step 2: Mechanism of the Reaction.
In the presence of sodium metal, the aryl halides undergo electron transfer from sodium to the halide, leading to the formation of phenyl radicals (C_6H_5·) or phenyl anions (C_6H_5−). These highly reactive intermediates then couple together at the ortho or para positions to form biphenyl (C_6H_5−C_6H_5). The sodium also reacts with the chlorine atoms to form sodium chloride (NaCl).
Step 3: Product Formed.
The major product of this reaction is biphenyl, which consists of two phenyl groups (C_6H_5) connected by a single bond. Biphenyl is an important compound in the chemical industry and is used in various applications such as in the synthesis of pharmaceuticals, pesticides, and as a heat transfer medium.
Final Answer:
The product formed in the Fittig reaction is biphenyl (C_6H_5−C_6H_5), and the reaction also produces sodium chloride (NaCl) as a byproduct.