Thiourea

Thiourea (/ˌθaɪoʊjʊəˈriːə/) 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, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. 'Thioureas' refers to a broad class of compounds with the general structure (R1R2N)(R3R4N)C=S. Thioureas are related to thioamides, e.g. RC(S)NR2, where R is methyl, ethyl, etc. Thiourea (/ˌθaɪoʊjʊəˈriːə/) 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, but the properties of urea and thiourea differ significantly. Thiourea is a reagent in organic synthesis. 'Thioureas' refers to a broad class of compounds with the general structure (R1R2N)(R3R4N)C=S. Thioureas are related to thioamides, e.g. RC(S)NR2, where R is methyl, ethyl, etc. Thiourea is a planar molecule. The C=S bond distance is 1.71 Å. The C-N distances average 1.33 Å. The weakening of the C-S bond by C-N pi-bonding is indicated by the short C=S bond in thiobenzophenone, which is 1.63 Å. Thiourea occurs in two tautomeric forms, of which the thione form predominates in aqueous solutions. The equilibrium constant has been Keq is 1.04×10−3. The thiol form, which is also known as an isothiourea, can be encountered in substituted compounds such as isothiouronium salts. The global annual production of thiourea is around 10,000 tonnes. About 40% is produced in Germany, another 40% in China, and 20% in Japan. Thiourea can be produced from ammonium thiocyanate, but more commonly it is produced by the reaction of hydrogen sulfide with calcium cyanamide in the presence of carbon dioxide. Thiourea per se has few applications. It is mainly consumed as a precursor to thiourea dioxide, which is a common reducing agent in textile processing. Other industrial uses of thiourea include production of flame retardant resins, and vulcanization accelerators.