Swarts reaction template

Bromomethane and silver fluoride exchange halogens: fluoride attacks the carbon from the back while Ag⁺ pulls off bromide as insoluble AgBr.

Mechanism step by step

An alkyl chloride or bromide heated with a metal fluoride gives the alkyl fluoride

1. Halogen exchange – F⁻ attacks from the back; Ag⁺ takes the leaving bromide (drawn as SN2)

Key points

• Used to make alkyl fluorides, which cannot be made by direct fluorination (too violent).
• Reagents: AgF, Hg₂F₂, CoF₂ or SbF₃ (SbF₃/SbCl₅ turns CCl₄ into the freon CCl₂F₂).
• Compare Finkelstein: NaI in acetone gives alkyl iodides by the same kind of exchange.
• The mechanism on solid metal fluorides is not fully settled; the step is drawn as SN2 with Ag⁺ assistance.

Drawn with 16 atoms, 4 arrows, 5 shapes – every one editable in MolDraw.

Sources

• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook