Optically active 2-iodo butane on treatment with `NaI` in acetone gives a product which does not show optical activity. Explain briefly.

Explanation

In this `S_(N)2` reaction, iodide acts as a nucleophile as well as the leaving group. Therefore, in this reaction, iodide displaces iodide. When 2-iodooctane (I) is treated with `I^(-)` ion, it undergoes stereochemical inversion to give 2-iodooctane (II) which is enantiomer of (I). Now (II) undergoes stereochemical inversion to give (I). This reaction is fast and occurs multiple times, each time inverting the stereochemistry. Ultimately, this results in a 50 : 50 (racemic mixture) of two enantiomers (I) and (II). In other words, optically active 2-iodooctane undergoes racemization.