Thiourea
Thiourea is an organosulfur compound with the formula SC(NH2)2. It is structurally similar to urea, except that the oxygen atom is replaced by a sulfur atom. The properties of urea and thiourea differ significantly, due to the greater polarizability of sulfur compared to oxygen. Thiourea is a versatile reagent in organic synthesis and coordination chemistry.
Properties:
Thiourea is a white, crystalline solid with a faint odor. It is soluble in water and ethanol but less soluble in nonpolar solvents. The molecule exists in two tautomeric forms: thiourea and isothiourea. In solution, thiourea is the predominant tautomer. It melts at around 176-178 °C.
Synthesis and Production:
Thiourea is industrially produced by the reaction of hydrogen cyanide with ammonium sulfide:
HCN + (NH4)2S → H2NCSNH2 + NH3
It can also be prepared by the reaction of ammonia with carbon disulfide.
Reactions and Applications:
Thiourea is a reducing agent. It is used in the manufacture of resins, vulcanization accelerators, and as a corrosion inhibitor. In photography, it is used as a fixing agent to remove silver halides from film. It also finds application in the synthesis of pharmaceuticals, dyes, and other organic compounds. Thiourea readily forms complexes with transition metals. These complexes have applications in catalysis and materials science. It can be used in organic synthesis to convert alkyl halides to thiols.
Safety:
Thiourea is considered a potential carcinogen and should be handled with care. It is also a mild irritant to the skin and eyes.