Notes on Exp. 20: "Reactivities of Some Alkyl Halides" (Pavia, 4 th ed.) Part A: Sodium Iodide in acetone, S N 2: Iodide ion, I-, from sodium iodide, can displace Br- or Cl- from an alkyl bromide or chloride. When NaI is dissolved in the aprotic solvent acetone, this reaction can only proceed via the S N 2 mechanism. Since both NaBr and NaCl are insoluble in acetone (only NaI is acetone soluble), a white precipitate in any of your test tubes in Part A will signal that S N 2 displacement has occurred. Watch the speed at which a precipitate is formed, if any, to determine which of your substrates will be good candidates for S N 2 reaction. Part B: Silver Nitrate in ethanol, S N 1: The combination of the ionizing solvent ethanol and the Ag + ion from dissolved silver nitrate provides the right conditions for an S N 1 type displacement of halides in Part B. The Ag
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