Explain the Finkelstein reaction and provide a balanced equation for the conversion of one haloalkane to another.

The Finkelstein reaction is an organic reaction used to convert an alkyl halide to another alkyl halide through an SN2 reaction. It was developed by German chemist Hans Finkelstein in 1910. The reaction involves the exchange of halide ions, and it is facilitated by the use of a polar, aprotic solvent such as acetone.

Here's a step-by-step explanation of the Finkelstein reaction:

1. The alkyl halide is dissolved in a polar, aprotic solvent such as acetone. This solvent is used because it can dissolve both the alkyl halide and the sodium halide salt, but it does not solvate the halide ions very well. This lack of solvation makes the halide ions more reactive.

2. Sodium halide is added to the solution. The halide ion from the sodium halide is a better nucleophile than the halide ion in the alkyl halide, so it attacks the carbon atom bonded to the halide in the alkyl halide.

3. This attack causes the carbon-halide bond in the alkyl halide to break, and a new carbon-halide bond is formed with the halide ion from the sodium halide. This is an SN2 reaction, so it occurs in a single step with inversion of configuration at the carbon atom.

4. The other product of the reaction is sodium halide, which precipitates out of the solution because it is less soluble in the polar, aprotic solvent than the other sodium halide. This drives the reaction to completion.

Here's a balanced equation for the Finkelstein reaction, using bromoethane and sodium iodide as an example:

C2H5Br + NaI → C2H5I + NaBr

In this reaction, bromoethane is converted to iodoethane, and sodium bromide is precipitated out of the solution.