In chemistry, the Halex process is used to convert aromatic chlorides to the corresponding aromatic fluorides. The process entails Halide exchange, hence the name. The reaction conditions call for hot solutions of the aryl chloride and anhydrous potassium fluoride. Typical solvents are dimethylsulfoxide, dimethylformamide, and sulfolane. Potassium chloride is generated in the process. The reaction is mainly applied to nitro-substituted aryl chlorides. Sometimes more soluble fluorides, such as caesium fluoride and TBAF are used.