In a
2-l. round-bottomed flask are mixed
152 g. (2 moles) of finely divided thiourea and 70 cc. of water. To this is added
138 g. (1.1 moles) of technical methyl sulfate (Note
1). The flask is immediately attached to a
long reflux condenser carrying a
trap. The reaction is allowed to progress spontaneously (Note
2), with occasional cooling as the reaction becomes more rapid and the flask becomes filled with vapor. After the initial vigorous reaction is completed, the mixture is refluxed for one hour, during which time crystallization takes place (Note
3). The mixture is then allowed to cool, the flask is removed,
200 cc. of 95 per cent ethyl alcohol is added, and the contents of the flask are then filtered with suction. The residue is washed twice with
100-cc. portions of 95 per cent alcohol and allowed to dry in air. The yield is
190 g. of a product which melts with decomposition at
235°. Another crop of crystals weighing
43 g. and melting at
230° can be obtained from the alcoholic filtrate by concentrating it to a paste to which, after cooling, is added
120 cc. of 95 per cent alcohol. The total yield is
220–233 g. (
79–84 per cent of the theoretical amount).