In a 1-l. round-bottomed three-necked flask, surrounded by an ice bath and fitted with a mechanical stirrer, a reflux condenser, thermometer, and a 250-ml. dropping funnel, are placed 137 g. (110 ml., 1.8 moles) of carbon disulfide and a cold solution of 72 g. (1.8 moles) of sodium hydroxide in 160 ml. of water. To this mixture, cooled to 10–15°, is added, with stirring, 180 ml. (56 g., 1.8 moles of methylamine) of 35% aqueous methylamine solution (Note 1) and (Note 2) over a period of 30 minutes. Stirring is continued, and the mixture is warmed gently on a steam bath for 1–2 hours to ensure complete reaction (Note 3). The bright red solution is cooled to 35–40°, and to it is added over a period of 1 hour, with stirring, 196 g. (175 ml., 1.8 moles) of ethyl chlorocarbonate (Note 4). The stirring is continued for 30 minutes after all the ethyl chlorocarbonate has been added, at which time the temperature should have fallen to 30–40°. The methyl isothiocyanate, which separates on top, is removed from the reaction mixture and weighs 170–190 g.

The product is dried over 10 g. of sodium sulfate and distilled under atmospheric pressure through a short Vigreux column; the fraction which boils at 115–121° is collected. The yield is 85–100 g. (65–76%) (Note 5) and (Note 6). The product may be further purified by refractionation. The portion which boils at 117–119° is collected.