In a
300-ml. three-necked, round-bottomed flask equipped with a
magnetic stirrer and a
gas-inlet tube reaching below the surface of the liquid is placed a solution of
63 g. (0.96 mole) of potassium hydroxide (Note
1) in 100 ml. of water. The solution is cooled in ice, and
hydrogen sulfide is bubbled through (Note
2) with stirring until the gain of weight is 33–34 g. (Note
3). The solution is then poured into a
3-l. three-necked, round-bottomed flask provided with a stirrer, a gas-inlet tube, a
reflux condenser, and a
thermometer reaching into the liquid. The small flask is rinsed with 25 ml. of ice water and the rinsings added to the rest of the solution. Then
63 g. (0.96 mole) of potassium hydroxide is added and allowed to dissolve. The
3-l. flask is then well flushed with
nitrogen and, at a temperature of about 30°,
76.0 g. (1.0 mole) of carbon disulfide (Note
4) is added at once. The mixture is stirred vigorously for 2 hours (Note
5) while
nitrogen is passed through at a rate of about one bubble per second (Note
6) and the temperature is kept at 35–38° (Note
7). Then the gas supply is disconnected and the dark-red solution is cooled in an
ice bath.
A solution of
189 g. (2.0 moles) of chloroacetic acid (Note
8) in 300 ml. of water is neutralized to litmus with a solution containing approximately
135 g. (2.1 moles) of potassium hydroxide in 300 ml. of water. The resulting
potassium chloroacetate solution is placed in a
dropping funnel and added to the stirred
potassium thiocarbonate solution obtained above at such a rate that the temperature does not go above 40°. After the addition is complete, the stirring is continued for 1 hour at room temperature. Then
200 ml. of concentrated hydrochloric acid is added while the temperature is kept below 20° by cooling in an ice bath. Finally, the reaction mixture is stirred for 30 minutes at room temperature. The yellow precipitate is filtered and washed twice with 150-ml. portions of ice water. The crude material is dried under reduced pressure in a
vacuum desiccator over
calcium chloride to constant weight (about 2 days). The drying is expedited if the lumps are occasionally broken up. The yield of yellow product having m.p.
169–174° (uncor.) (Note
9) is
152–160 g. (
67–71%).