The Finkelstein reaction uses acetone and a metal halide salt to exchange the halogen atom of an alkyl halide for another halogen atom via an SN2 reaction. The substituted metal halide being less soluble than the original metal halide in acetone (Le Chatelier’s principle) drives the reaction forward.

  • Reagents: Acetone, Metal Halide Salt
  • Reactant: Alkyl Halide
  • Product: Substituted Derivative
  • Type of Reaction: SN2

Lab Tips

  • Alkyl bromides, chlorides, tosylates and mesylates readily convert to the corresponding alkyl iodides, which are often difficult to prepare by other methods. [1]
  • Due to the stability of alkyl fluorides, they are often sluggish to participate in SN2 reactions. One way to displace fluorine in alkyl fluorides with iodide is to use iodotrimethylsilane. [2]
  • Primary, secondary, allylic or benzylic halides work best. Sterically hindered secondary and tertiary alkyl halides can be converted to alkyl iodides by treatment with NaI/CS2 in the presence of various Lewis acids such as AlMe3, ZnCl2, FeCl3, etc. [3]
  • α-halogenated ketones and acids also undergo this reaction with ease. [1]
  • Microwave irradiation at high pressure increases the rate of reaction. [4]
1. Kürti, L., Czakó, B. (2005). Strategic Applications of Named Reactions in Organic Synthesis; Background and Detailed Mechanisms. Burlington, MA: Elsevier Academic Press.
2. Olah, G. A., Narang, S. C., Field, L. D. Synthetic methods and reactions. 103. Preparation of alkyl iodides from alkyl fluorides and chlorides with iodotrimethylsilane or its in situ analogs. J. Org. Chem. 1981, 46, 3727-3728.
3. Miller, J. A., Nunn, M. J. Synthesis of alkyl iodides. J. Chem. Soc., Perkin Trans. 1 1976, 416-420.
4. Williams, R., Kennedy, A., Hijji, Y., Tadesse, S. Finkelstein halogen exchange reaction using microwave energy and a binary solvent system. Proceedings – NOBCChE 2001, 28, 58-63.


Top Citations

Original Paper

Related Reactions

  • Nucleophilic Substitution

Related Compounds

By shuhan yang


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