Question

What is the mechanism of the reaction of NaI in acetone with an alkyl halide?

Answer 1

This operates by the `S_(N)2` mechanism. The iodide ion is a reasonably good nucleophile, and adds as `I^-`

Explanation:

`R-Cl + Na^+I^-` `rarr` `R-I + NaCldarr`

Because sodium iodide is much more soluble than sodium chloride in acetone, when you do this you see a glassy precipitate of sodium chloride in the acetone. I think there is a named organic spot test for this reaction (its name escapes me at the moment, I should not have finished that bottle of wine last night!). If you have time in an organic laboratory it would be worth your while to do this reaction in a small test tube so you can notice the turbidity of the sodium chloride when it precipitates.