In a
1-l. three-necked round-bottomed flask fitted with an
efficient stirrer, a
dropping funnel, and a
thermometer, are placed
150 g. (82 ml., 1.5 moles) of 98% sulfuric acid (Note
1) and
1 g. of flowers of sulfur. To this is added, with rapid stirring,
85 g. (91 ml., 1 mole) of acetone cyanohydrin1 (Note
2) over a period of 25 minutes, the temperature of the contents of the flask being kept at 75–80° by cooling in a
water bath. At the end of this period, the water bath is replaced with an
oil bath preheated to 160°. With continued stirring, the temperature of the reaction mixture is raised to 150° within 5 minutes and maintained at 150° for 15 minutes (Note
3). The reaction mixture is quickly cooled to room temperature by replacing the oil bath with an
ice bath and is then poured into 300 ml. of cold water, and the flask is rinsed with 75 ml. of water. The diluted mixture is filtered (Note
4) through a
10-cm. Büchner funnel with the aid of suction. The filtrate is placed in a
1-l. beaker, cooled with an ice bath and
180–190 g. of anhydrous sodium carbonate sifted in with vigorous stirring (
Caution! foaming) (Note
5). The precipitate is collected on a
20-cm. Büchner funnel and pressed and sucked as dry as possible. The crude product is dried in a
vacuum desiccator over anhydrous
calcium chloride for 36–48 hours (Note
6). The light cream- or tan-colored crude product weighs
300–400g.
The crude dried soild is crushed to break up lumps and is placed in a
2-l. flask and heated and stirred mechanically with
500 ml. of boiling benzene. The solution is decanted, and the extraction is repeated four times using
200-ml. portions of benzene. The combined
benzene solutions are heated to boiling, treated with
2–4 g. of Norit, and filtered. On cooling,
48–52 g. of
methacrylamide separates; m.p.
105–107° (Note
7). An additional
5–8 g., m.p.
103–105°, is obtained when the mother liquor is concentrated to 150 ml. and cooled. The yield of
methacrylamide is
52–60 g. (
61–70%) after storing in a vacuum desiccator over paraffin wax and anhydrous
calcium chloride.