The Finkelstein reaction, named for the German chemist Hans Finkelstein, is an SN2 reaction that involves the exchange of one halogen atom for another. The SN2 reaction (also known as bimolecular nucleophilic substitution) is a type of Nucleophilic substitution, where a lone pair from a Nucleophile Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions Halide exchange is an equilibrium reaction, but the reaction can be driven to completion by taking advantage of differential solubility of halide salts, or by using a large excess of the halide salt. In a Chemical process, chemical equilibrium is the state in which the chemical activities or Concentrations of the reactants and products have no net change
- R-X + X'- ⇌ R-X' + X-
The classic Finkelstein reaction involves the conversion of an alkyl chloride or an alkyl bromide to an alkyl iodide by the addition of sodium iodide in acetone. The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane Sodium iodide is a white Crystalline Salt with Chemical formula Na[[Iodine I]] used in radiation detection treatment of Iodine deficiency Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless mobile flammable Because sodium iodide is soluble in acetone and sodium chloride and sodium bromide are not, the equilibrium is shifted by the precipitation of the insoluble salt. For sodium chloride in the diet see Salt. Sodium chloride, also known as common salt, table salt, or Halite, is a Sodium bromide, also known as sedoneural is a Salt with the formula Na[[bromine Br]] widely used as an Anticonvulsant and a Sedative For example, bromoethane can be converted to iodoethane:
- CH3CH2Br + NaI → CH3CH2I + NaBr
Alkyl halides differ greatly in the ease with which they undergo the Finkelstein reaction. Bromoethane, also known as ethyl bromide is a Chemical compound of the Haloalkanes group Ethyl iodide (also iodoethane) is a Colorless, Flammable Chemical compound. The reaction works well for primary (except for neopentyl) halides, and exceptionally well for allyl, benzyl, and α-carbonyl halides. Neopentane, also called dimethylpropane or 22-dimethylpropane, is a double-branched-chain Alkane with five Carbon atoms An allyl group is an Alkene Hydrocarbon group with the formula H2C=CH-CH2- In Organic chemistry, benzyl is the term used to describe the Substituent or molecular fragment possessing the structure C6H5CH2- Secondary substrates are marginal. Vinyl, aryl and tertiary alkyl halides are unreactive. A vinyl compound is any Organic compound that contains a vinyl group (also called ethenyl) &minus C[[Hydrogen H]] =CH sub>2 In the context of organic molecules aryl refers to any Functional group or Substituent derived from a Simple aromatic ring, may it be Phenyl Below some relative rates of reaction (NaI in acetone at 60°):[1][2]
| Me-Cl | Bu-Cl | i-Pr-Cl | t-BuCH2-Cl | CH2=CH-CH2-Cl | PhCH2-Cl | EtOC(O)CH2-Cl | MeC(O)CH2-Cl |
|---|---|---|---|---|---|---|---|
| 179 | 1 | 0. 0146 | 0. 00003 | 64 | 179 | 1600 | 33000 |
In modern usage the definition of the reaction has been expanded to include the conversion of alcohols to alkyl halides by first converting the alcohol to a sulfonate ester (tosylates or mesylates are usually used), and then performing the substitution. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon A sulfonate ion is an ion that contains the -S(=O2-O&minus Functional group. A tosyl group (abbreviated Ts or Tos) combines the Toluene and Sulfonyl Functional groups. In Chemistry, a mesylate is any Salt or Ester of Methanesulfonic acid ( C[[Hydrogen H]]3 S[[Oxygen O]]3H The example below is from a synthesis of Chrysochlamic Acid. [3]
References
- ^ "Solvolytic Displacement Reactions at Saturated Carbon Atoms," Streitwieser, A. Chem. Rev. 1956, 56, 571
- ^ "The Effect of the Carbonyl and Related Groups on the Reactivity of Halides in SN2 Reactions" Bordwell, F. G. ; Brannen, W. T. J. Am. Chem. Soc. 1964, 86, 4645
- ^ Maloney, D. J. ; Hecht, S. M. Org. Lett. 2005, 7,4297
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