Formation of Iodobenzene from Diazonium Salt and KI

When diazonium salt undergoes reaction with KI, it forms iodobenzene. This reaction is an example of a Sandmeyer reaction.

The Sandmeyer reaction involves the conversion of an aryl diazonium salt to a different functional group by substitution. The reaction typically involves the use of a copper(II) salt as a catalyst and an acidic solution.

Mechanism of the Reaction

The reaction proceeds in the following steps:

Step 1: Formation of Copper(I) Iodide

KI reacts with CuSO4 to form CuI, which is the catalyst for the reaction.

CuSO4 + 2KI → CuI + K2SO4

Step 2: Formation of Aryl Iodide

The diazonium salt reacts with CuI to form an aryl iodide.

ArN2+X- + CuI → ArI + CuX + N2

Step 3: Regeneration of the Catalyst

The reaction also involves the regeneration of the catalyst by reacting with the by-product CuX.

CuX + HX → CuX2

Overall Reaction

The overall reaction can be represented as:

ArN2+X- + CuI + 2KI → ArI + CuI2 + K2SO4 + N2

Conclusion

The reaction of diazonium salt with KI is an example of a Sandmeyer reaction. It involves the conversion of an aryl diazonium salt to a different functional group by substitution. In this case, the reaction results in the formation of iodobenzene. The reaction proceeds via the formation of copper(I) iodide, which acts as a catalyst for the reaction.