PURPOSE:To substitute an organic compound having active chlorine or bromine with fluorine in high yield without side reactions even under conditions in which the conventional KF is unreactive, by using fine particulate anhydrous potassium fluoride obtained by the spray drying method in an aprotic organic solvent. CONSTITUTION:An organic compound having an active chlorine or bromine is substituted by fluorine in an aprotic organic solvent by using potassium fluoride. In the process, fine particulate anhydrous potassium fluoride having 1-50mu particle diameter obtained by the spray method is used. The anhydrous potassium fluoride is obtained by spraying a concentrated aqueous solution synthesized by neutralizing hydrofluoric acid with KOH, etc. in hot air at 300-600 deg.C in a spray dryer, drying the solution instantaneously, and recovering the dried particles from the hot air by a cyclone. The resultant KF has very slight hygroscopicity, and can be converted into a low-boiling solvent even in a system in which the reaction is carried out only in a high-boiling solvent. Thus, side reactions can be suppressed. The equipment can be also simplified.
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