In a 1-l. three-necked flask, equipped with a stirrer and a thermometer and immersed in an ice bath, is placed 46 g. (0.7 mole) of sodium azide (Note 1) in 150 ml. of water. A mixture of 109 g. (0.5 mole) of lauroyl chloride (b.p. 134–137°/11 mm.) and 150 ml. of acetone is then added from a separatory funnel to the well-stirred solution of the azide at such a rate that the temperature remains at 10–15°. After the mixture has been stirred at this temperature for an hour, the stirrer is stopped and, when the layers have separated, the lower water layer is removed carefully by suction through a glass capillary tube (Note 2). The upper layer is then added slowly to 500 ml. of benzene which has been warmed to 60° (Note 3). A rather rapid evolution of gas results, and the mixture is kept at 60–70° (Note 4) until no more nitrogen is evolved; the conversion of azide to isocyanate requires about an hour. The solution is filtered to remove any insoluble matter, and the benzene is removed by distillation from a modified Claisen flask. Distillation of the residue yields 80–85 g. of ester (81–86%) (Note 5) and (Note 6).