>>7613898The inital step for sarin synthesis, or any other organophosphorus compounds is the synthesis of phosphorus trichloride.
>The action of chlorine on white or red phosphorus on heating in a retort, and condensing the phosphorus trichloride vapour in a cooled dry receiver.
>Molten white phosphorus and gaseous chlorine react in previously produced phosphorus trichloride. The formation of phosphorus pentachloride is prevented by the presence of a small excess of phosphorus. The heat of reaction, ca. 10 times the heat of evaporation, keeps the system at its boiling point, and the phosphorus trichloride distills off. The vapors are fractionated as reflux takes place, and the Cl3P condenses in air-cooled condensers. The rate of removal of Cl3P (i.e. the production rate) is equivalent to the feed rate of phosphorus and chlorine. The process is controlled by the boiling temperature, which is determined by the phosphorus content. The rate of chlorine flow is fixed, and the phosphorus feed rate is adjusted manually. The phosphorus trichloride produced contains no free phosphorus and needs no further treatment.
>Phosphorus trichloride is made by reacting yellow phosphorus with chlorine.
Distillation is required for higher purity.
