Question

What is halide exchange method for the preparation of iodoalkanes?

Answer 1

The halide exchange method for preparing iodoalkanes is known as the Finkelstein reaction. In this reaction, a chloroalkane or bromoalkane is converted into an iodoalkane by reaction with an alkali metal iodide (usually sodium iodide, NaI) in dry acetone.

• Reactants: An alkyl chloride (R − Cl) or alkyl bromide (R − Br) is used as the starting material.
• Reagent: A solution of sodium iodide (NaI) is used.
• Solvent: Dry acetone is used as a polar aprotic solvent.
• Conditions: The mixture is typically heated, often under reflux conditions.

The general chemical equation is

\[\ce{R - X + NaI → R - I + NaX}\] (precipitates out in acetone)

Thus, the halide exchange method provides a convenient and practical route for the preparation of iodoalkanes from alcohol-derived alkyl chlorides or bromides.