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Org. Synth. 1949, 29, 61
DOI: 10.15227/orgsyn.029.0061
METHACRYLAMIDE
Submitted by Richard H. Wiley and Walter E. Waddey.
Checked by R. L. Shriner and Arne Langsjoen.
1. Procedure
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.
2. Notes
1. Acid of 98% strength may be prepared by the addition of 33.5 ml. of fuming sulfuric acid (15% SO3) to 48 ml. of concentrated sulfuric acid of sp. gr. 1.84.
2. Acetone cyanohydrin of 98% purity may be purchased from the Rohm and Haas Company, Philadelphia, Pennsylvania.
3. This heating converts the intermediate compounds into methacrylamide sulfate. Longer periods of heating decrease the yield.
4. A small amount of dark polymeric material, which may form, is separated at this point.
5. Care is taken to crush lumps of sodium carbonate formed during the addition. The final reaction mixture should be slightly alkaline to litmus paper, and the temperature of the mixture should not rise above 25–30°.
6. The precipitated methacrylamide contains varying amounts of sodium sulfate. It is essential to obtain a dry product for the benzene extraction. The desiccator should be evacuated with an oil pump to about 5 mm. several times during 24–36 hours in order to obtain a sufficiently dry material.
7. The methacrylamide tends to retain some solvent. By placing the product in a vacuum desiccator containing paraffin wax shavings and anhydrous calcium chloride for 36–48 hours material with a melting point of 109–110° may be obtained.
3. Discussion
Methacrylamide has been prepared by the reaction of acetone cyanohydrin with concentrated sulfuric acid2,3,4,5,6,7 and sulfuric acid with ammonium sulfate,8 and by the hydrolysis of methacrylonitrile.9 The method described is an adaptation of that of Crawford and McGrath.4

References and Notes
  1. Org. Syntheses Coll. Vol. 2, 7 (1943).
  2. Verhulst, Bull. soc. chim. Belg., 39, 563 (1930); 40, 475 (1931).
  3. Crawford, J. Soc. Chem. Ind., 64, 231 (1945).
  4. Crawford and McGrath, U. S. pat. 2,140,469 [C. A., 33, 2536 (1939)]; Brit. pat. 440,967 [C. A., 30, 4180 (1936)]
  5. Crawford and Grigor, U. S. pat. 2,101,822 [C. A., 32, 952 (1938)]; Brit. pat. 456,533 [C. A., 31, 2230 (1937)].
  6. I. G. Farbenind. A.-G., Fr. pat. 813,844 [C. A., 32, 953 (1938)].
  7. Rohm und Haas A.-G., Fr. pat. 815,908 [C. A., 32, 1816 (1938)].
  8. U. S. pat. 2,431,468 [C. A., 42, 3429 (1948)].
  9. Bruylants and Castille, Bull. sci. acad. roy. Belg., 13, 767 (1928) [C. A., 27, 2366 (1928)].

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

SO3

calcium chloride (10043-52-4)

sulfuric acid (7664-93-9)

Benzene (71-43-2)

sodium carbonate (497-19-8)

sodium sulfate (7757-82-6)

sulfur (7704-34-9)

Norit (7782-42-5)

ammonium sulfate (7783-20-2)

Acetone cyanohydrin (75-86-5)

Methacrylamide (79-39-0)

methacrylamide sulfate

methacrylonitrile (126-98-7)