In a previous note1 we have described a method for the preparation of the important insecticidal compound O,O-diethyl O-p-nitrophenyl thiophosphate which is now called "parathion." The method was based upon the synthesis used by Schrader2 who first prepared the compound and
Notes 3943 Physical Constants Molecular weight Crystalline form and color Melting point Solubility (g./lOO ml.) Water, 20°W ater, 100°9 5% ethyl alcohol, 20 °Ether (anhydrous), 20°A cetone (anhydrous), 20°3 36.85 Amorphous white powder ; slightly hygroscopic Caramelization begins at 270°8 .9 21.5 1.5 0.015 0.004 Notes Vol. 70found that comparable yields could be obtained in a much shorter time if ethanol or water was used as the solvent.A mixture of 0,0-diethyl chlorothiophosphate (37.7g.), anhydrous sodium p-nitrophenoxide (32.2 g.), and ethanol (200 cc.) was refluxed for on! hour, cooled to 20°, filtered, and the filtrate concentrated in vacuo. The residue was heated (oil-bath at 100-110°) with stirring at 0.5 mm. for a short period to remove any unreacted 0,0-diethyl chlorothiophosphate. The crude parathion was dissolved in toluene (100 cc.) and washed with 5% sodium carbonate, then with water. After drying over Drierite and removal of the toluene at reduced pressure, the product weighed 43.5 g. (75% yield), »26d 1.5361. Distillation of a 200-g, sample prepared in another experiment gave 182 g. of pale yellow oil, b. p. 157-162°( 0.6 mm.), w25d 1.5370.
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