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Org. Synth. 1948, 28, 89
DOI: 10.15227/orgsyn.028.0089
α-PHENYLTHIOUREA
[Urea, 1-phenyl-2-thio-]
Submitted by Robert L. Frank and Paul V. Smith1.
Checked by Richard T. Arnold and Sherman Sundet.
1. Procedure
In a 500-ml. three-necked flask fitted with a reflux condenser, a mechanical stirrer, and a 100-ml. dropping funnel are placed 17 g. (0.22 mole) of ammonium thiocyanate and 100 ml. of dry acetone (Note 1). Through the dropping funnel is added, with stirring, 28.2 g. (0.2 mole) of benzoyl chloride. After the addition is complete, the mixture is refluxed for 5 minutes. Then a solution of 18.6 g. (0.2 mole) of aniline in 50 ml. of dry acetone is added at such a rate that the solution refluxes gently. The mixture is poured carefully with stirring into 1.5 l. of water, and the resulting yellow precipitate (α-benzoyl-β-phenylthiourea) is separated by filtration. The crystals are heated for 5 minutes with a boiling solution of 30 g. of sodium hydroxide in 270 ml. of water. After the removal of a small amount of insoluble material by filtration, the solution is acidified with concentration hydrochloric acid and then made slightly basic with ammonium hydroxide. Upon standing, the solution deposits the crystalline product. The yield of oven-dried material (m.p. 151–153°) is 25.8 g. (85%). Recrystallization from ethanol yields 23.2 g. (76%) of white plates melting at 152.5–153°.
2. Notes
1. The acetone is dried for at least 48 hours over anhydrous calcium sulfate (Drierite) and distilled just before it is used.
3. Discussion
α-Phenylthiourea has been prepared by the action of ammonium thiocyanate,2 thiocyanic acid,3 thiuramdisulfide,4 or silicon thiocyanate5 on aniline; by the action of ammonium thiocyanate on aniline hydrochloride;6 by the action of ammonia on phenyl isothiocyanate,7 1-phenyl-2-thiobiuret,8 thiocarbanilide,9 phenyldithiocarbamazide,10 or phenyl isothiocyanate hexasulfide;11 by the addition of hydrogen sulfide to monophenylcyanamide;12 by the decomposition of salts of phenyldithiocarbamic acid in the presence of lead carbonate,13 ammonium polysulfide,14 or ammonium carbonate;15 by the reaction of thiophosgene, aniline, and ammonia;16 and by the action of hydrazine hydrate on phenyldithiobiuret.17
The preparation of α-phenylthiourea by the procedure described herein has not been reported, although Douglass and Dains18 have applied the method to the preparation of various substituted phenyl derivatives.
This preparation is referenced from:

References and Notes
  1. Work done under contract with the Office of Rubber Reserve.
  2. Schiff, Ann., 148, 338 (1868); Rathke, Ber., 18, 3102 (1885).
  3. Salkowski, Ber., 24, 2724 (1891); Challenger and Collins, J. Chem. Soc., 125, 1377 (1924); DeBeer, Buck, Ide, and Hjort, J. Pharmacol., 57, 19 (1936).
  4. Klason, J. prakt. Chem., [2] 36, 57 (1887); Fromm, Ber., 42, 1955 (1909).
  5. Reynolds, J. Chem. Soc., 89, 397 (1906).
  6. deClermont, Ber., 9, 446 (1876); Liebermann, Ann., 207, 122 (1881); Bertram, Ber., 25, 48 (1892); Ger. pat. 604,639, French pat. 762,310 [C. A., 29, 819 (1935)]; Krall and Gupta, J. Indian Chem. Soc., 12, 629 (1935).
  7. Hofmann, Compt. rend., 47, 424 (1858); Otterbacher and Whitmore, J. Am. Chem. Soc., 51, 1909 (1929).
  8. Birckenbach and Kraus, Ber., 71, 1492 (1938).
  9. Gebhardt, Ber., 17, 3043 (1884); v. Walther and Stenz, J. prakt. Chem., [2] 74, 223 (1906).
  10. Oliveri-Mandala, Gazz. chim. ital., 51, II, 195 (1921).
  11. Levi, Gazz. chim. ital., 61, 619 (1931).
  12. Weith, Ber., 9, 810 (1876).
  13. Heller and Bauer, J. prakt. Chem., [2] 65, 365 (1902).
  14. Azzalin, Gazz. chim. ital., 55, 895 (1925).
  15. Drozdov, J. Gen. Chem. U.S.S.R., 6, 1368 (1936).
  16. Hutin, Rev. gén. mat. plastiques, 7, 95 (1931).
  17. Fromm, Ann., 426, 326 (1922).
  18. Douglass and Dains, J. Am. Chem. Soc., 56, 1408 (1934).

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

phenyl isothiocyanate hexasulfide

ammonium polysulfide

α-Phenylthiourea

α-benzoyl-β-phenylthiourea

salts of phenyldithiocarbamic acid

ethanol (64-17-5)

hydrochloric acid (7647-01-0)

ammonium carbonate (506-87-6)

ammonia (7664-41-7)

ammonium thiocyanate (1762-95-4)

aniline (62-53-3)

sodium hydroxide (1310-73-2)

hydrogen sulfide (7783-06-4)

aniline hydrochloride (142-04-1)

calcium sulfate (7778-18-9)

acetone (67-64-1)

benzoyl chloride (98-88-4)

Thiophosgene (463-71-8)

ammonium hydroxide (1336-21-6)

hydrazine hydrate (7803-57-8)

PHENYL ISOTHIOCYANATE (103-72-0)

Urea, 1-phenyl-2-thio- (103-85-5)

thiocarbanilide (102-08-9)

thiocyanic acid (463-56-9)

thiuramdisulfide

silicon thiocyanate

1-Phenyl-2-thiobiuret (53555-72-9)

phenyldithiocarbamazide

monophenylcyanamide

phenyldithiobiuret

lead carbonate