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

This operates by the ${S}_{N} 2$ mechanism. The iodide ion is a reasonably good nucleophile, and adds as ${I}^{-}$
$R - C l + N {a}^{+} {I}^{-}$ $\rightarrow$ $R - I + N a C l \downarrow$