The Finkelstein Reaction is a specific method for preparing alkyl iodides from alkyl chlorides or bromides.

• Reaction: $R-X+NaI\stackrel{\text{acetone}}{\to }R-I+NaX\downarrow$ (where $X=Cl,Br$)
• Mechanism: It follows an $S_{N}2$ pathway.
• Driving Force: Sodium chloride and sodium bromide are insoluble in dry acetone and precipitate out. This shifts the equilibrium forward according to Le Chatelier's principle.
• This is a classic example of Halogen Exchange.