The partial fluorination of nonpolar organic polyhalides (mostly aliphatic) withantimony trifluoridein the presence ofantimony pentachlorideorchlorineis generally referred to as the Swarts reaction and the mixture ofantimony trifluorideandchlorine(SbF3+ Cl2) is known as the Swarts reagent. It has been reported that only aryl halides carrying more than one electron-withdrawing group (e.g., NO2) on the aromatic ring can react with fluoride. Furthermore, this reaction is not likely to take place under the reduced pressure. After fluorination, it has been found that the resulting fluoride has a lower boiling point than the corresponding chloride and this phenomenon is known as the Swarts rule. This reaction has been modified by the addition of fluorine, halogen fluoride, fluorides of noble gases and is useful for the preparation of organic fluorides.

Examplesoftheproductsobtainedthroughthisprocessareseeninthefollowingreactions:

CCl4→CF2Cl2+CFCl3

CHCl3→CHFCl2+CHF2Cl

CCl3CCl3→CFCl2-CFCl2+CFCl2-CF2Cl

C6H5CCl3→C6H5CF3