Tetrachlorophthalic anhydride (CAS No.: 117-08-8) is an important intermediate in organic synthesis. Phthalic anhydride (phthalic anhydride) is used as a raw material and undergoes chlorination reactions under different conditions, specifically including three variants:
Solvent method: Using fuming sulfuric acid or chlorosulfonic acid as a solvent and iodine or iodine chloride as a catalyst, dry chlorine gas is passed through at 70–150℃. The reaction time is typically around 16 hours, with a stable yield of over 80%.
Melting method: Phthalic anhydride is chlorinated in the molten state, using metals such as Mg, Fe, and Sb as catalysts, by directly passing chlorine gas through the chlorination process.
Gas-phase chlorination method: At high temperatures of 200–400℃, using Lewis acids such as FeCl₃ and CoCl₂ as catalysts, phthalic anhydride undergoes a gas-phase electrophilic substitution reaction with chlorine gas.
