A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1937, 17, 16
DOI: 10.15227/orgsyn.017.0016
Submitted by N. A. Lange and F. E. Sheibley.
Checked by W. W. Hartman and J. B. Dickey.
1. Procedure
In a 3-l. beaker a mixture of 20 g. (0.146 mole) of anthranilic acid, 700 cc. of warm water (35°), and 11 cc. (11.6 g., 0.19 mole) of glacial acetic acid is stirred mechanically and allowed to cool to room temperature. A freshly prepared solution of 15 g. (0.185 mole) of potassium cyanate (Note 1) in 50 cc. of water is then added dropwise with stirring over a period of fifteen to twenty minutes (Note 2). The resulting pasty mixture is stirred for twenty minutes, and then 200 g. (5 moles) of flaked sodium hydroxide (Note 3) is added slowly in small portions. During this addition the reaction mixture is kept below 40° by cooling in a cold-water bath. A clear solution is obtained momentarily, but in a short time a fine granular precipitate of the hydrated monosodium salt of benzoylene urea precipitates. After the mixture has cooled overnight in an ice box, the precipitated sodium salt is collected on a Büchner funnel, using a hardened filter paper (Note 4). The colorless salt is dissolved in 1 l. of hot water (90–95°), and the solution is filtered and heated to boiling in a 3-l. beaker. The benzoylene urea is precipitated by adding dilute sulfuric acid (1:1) with vigorous stirring until the liquor is acid to litmus. The product separates as a hydrate which forms small, lustrous, colorless needles. The material is collected on a Büchner funnel, washed with 200 cc. of water, and dried in an oven at 100°. The yield is 19.5–20.5 g. (82–87 per cent of the theoretical amount) (Note 5).
2. Notes
1. The yield is highly dependent upon the quality of the potassium cyanate employed, and some samples were found worthless for the purpose. The yields given were realized using Eastman's regular grade of potassium cyanate.
2. If the addition is too rapid the odor of isocyanic acid (remindful of that of sulfur dioxide) becomes strong and the yield is diminished.
3. The commercial grade of flaked sodium hydroxide dissolves readily and is convenient to handle. Any silica present is not objectionable since it is removed by filtering the redissolved sodium salt before precipitating the product with acid.
4. Schleicher and Schüll's hardened filters (No. 575, 9 cm.) are satisfactory.
5. The melting point of benzoylene urea is above 350°.
3. Discussion
Benzoylene urea has been prepared by passing cyanogen into a solution of anthranilic acid in alcohol and hydrolyzing the resulting 2-ethoxy-4-ketodihydroquinazoline;1 by fusing anthranilic acid with urea;2, 3 and by the action of aqueous cyanic acid on anthranilic acid.2, 3, 4, 5 The procedure described is adapted from that of Bogert and Scatchard5 with several modifications.

References and Notes
  1. Griess, Ber. 2, 415 (1869).
  2. Griess, J. prakt. Chem. (2) 5, 371 (1872).
  3. Bogert and Scatchard, J. Am. Chem. Soc. 41, 2056 (1919).
  4. Gabriel and Colman, Ber. 38, 3561 (1905); Scott and Cohen, J. Chem. Soc. 119, 664 (1921).
  5. Bogert and Scatchard, J. Am. Chem. Soc. 38, 1611 (1916).

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



sulfuric acid (7664-93-9)

acetic acid (64-19-7)

sodium hydroxide (1310-73-2)

sulfur dioxide (7446-09-5)


urea (57-13-6)

Anthranilic Acid (118-92-3)

potassium cyanate (590-28-3)

Benzoylene urea (86-96-4)

isocyanic acid (75-13-8)


cyanic acid (420-05-3)

monosodium salt of benzoylene urea