Organic Syntheses, Coll. Vol. 4, p.78 (1963); Vol. 33, p.13 (1953).
Five grams of potassium hydroxide (85% KOH)
is dissolved in 100 ml. of methyl Cellosolve (Note 1)
in a 500-ml. flask (Note 2)
fitted with a mechanical stirrer
, reflux condenser
, and a heating mantle
. Dicyandiamide (50.4 g.; 0.6 mole) (Note 3)
and benzonitrile (50 g.; 0.48 mole)
are added, and the mixture is stirred and heated. A solution is formed, and, when the temperature reaches 90–110°, an exothermic reaction begins and the product separates as a finely divided white solid. The vigor of the reaction is kept under control by the refluxing of the solvent (Note 4)
When the exothermic reaction is ended, the slurry of product is stirred and refluxed for 5 hours to ensure complete reaction (Note 5)
. The mixture is then cooled and filtered. The product is washed by suspension in hot water (Note 6)
, filtered, and dried. The yield is 68–79 g.
). The product melts at 227–228° (Note 7)
The commercial solvent is used without purification. Other primary alcohols of similar or higher boiling point are suitable solvents.
The large flask is chosen to allow for better stirring and heat transfer.
The reaction may be carried out with exactly molar equivalents of reactants. Slightly better yields are obtained by using the 0.2 to 0.25 molar excess of dicyandiamide
Boiling of the methyl Cellosolve
dissipates the heat of reaction, which begins at about 90°. The submitters state that, in one preparation using 100 times the indicated quantities (21-l. flask
), two condensers were used and intermittent cooling of the flask with a small stream of water kept the boiling from becoming too violent.
Yields reported were obtained after 5 hours under reflux. Preparation of other guanamines indicates an optimum yield after 2.5 hours under reflux.
Thorough washing with hot water serves to remove any dicyandiamide
which may be present in the crude product. Benzoguanamine
is slightly soluble in hot water.
filtrate may be evaporated to obtain further quantities of product, m.p. 227–228°
, raising the total yield to 90–95%.
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