Swarts Reaction — the NEET Chemistry reaction: mechanism, reagents, conditions, structures and exam traps.
Swarts Reaction The Swarts reaction is the preparation of alkyl fluorides by heating an alkyl chloride or bromide with a metallic fluoride such as silver fluoride (AgF), mercurous fluoride (Hg₂F₂), or antimony trifluoride (SbF₃). It is the standard method for introducing fluorine into organic molecules. A white precipitate of AgCl (or pale yellow AgBr) forms as the reaction proceeds. The reaction mixture is typically heated under reflux for several hours. The reaction is driven by the precipitation of AgCl/AgBr (highly insoluble), which shifts the equilibrium strongly to the right. The C-F bond formed (485 kJ/mol) is stronger than the C-Cl bond broken (339 kJ/mol), making the reaction thermodynamically favorable. The fluoride ion (F⁻) from AgF acts as a nucleophile F⁻ attacks the electrophilic carbon bearing the chlorine/bromine The C-Cl or C-Br bond breaks heterolytically as the C-F bond forms AgCl or AgBr precipitates out (Le Chatelier drives the reaction forward) Confusing Swarts reaction with Finkelstein reaction — Swarts uses AgF for fluorination, Finkelstein uses NaI for iodination. Thinking any fluoride salt works — KF or NaF are much less effective because their halide byproducts (KCl, NaCl) are soluble and don't precipitate to drive the reaction. Forgetting the industrial application — Freon-12 (CCl₂F₂) is made by Swarts reaction of CCl₄ with SbF₃.