the corresponding diols. The intermediate of the reaction is an unstable endoperoxide. Thiourea is also used in the reductive workup of ozonolysis to give carbonyl compounds. Dimethyl sulfide is also an effective reagent for this reaction, but it is highly volatile (boiling point ) and has an obnoxious odor whereas thiourea is odorless and conveniently non-volatile (reflecting its polarity). Source of sulfide Thiourea is employed as a source of sulfide, such as for converting alkyl halides to thiols. The reaction capitalizes on the high nucleophilicity of the sulfur center and easy hydrolysis of the intermediate isothiouronium salt: CS(NH2)2 + RX → + 2 NaOH → RSNa + OC(NH2)2 + NaX + H2O RSNa + HCl → RSH + NaCl In this example, ethane-1,2-dithiol is prepared from 1,2-dibromoethane: C2H4Br2 + 2 SC(NH2)2 → [C2H4(SC(NH2)2)2]Br2 [C2H4(SC(NH2)2)2]Br2 + 2 KOH → C2H4(SH)2 + 2 OC(NH2)2 + 2 KBr Like other thioamides, thiourea can serve as a source of sulfide upon reaction with metal ions. For example, mercury sulfide forms when mercuric salts in aqueous solution are treated with thiourea: Hg2+ + SC(NH2)2 + H2O → HgS + OC(NH2)2 + 2 H+ These sulfiding reactions, which have been applied to the synthesis of many metal sulfides, require water and typically some heating. Precursor to heterocycles Thioureas are building blocks to pyrimidine derivatives. Thus thioureas condense with β-dicarbonyl compounds. The amino group on the thiourea initially condenses with a carbonyl, followed by cyclization and tautomerization. Desulfurization delivers the pyrimidine. Similarly, aminothiazoles can be synthesized by the reaction of α-haloketones and thiourea. The pharmaceuticals thiobarbituric acid and sulfathiazole are prepared using thiourea. 4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole is prepared by the reaction of thiourea and hydrazine. Silver polishing According to the label on consumer products TarnX and Silver Dip, the liquid silver cleaning products contain thiourea along with a warning that thiourea is a chemical on California's list of carcinogens. A lixiviant for gold and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. Kurnakov reaction Thiourea is an essential reagent in the Kurnakov test used to differentiate cis- and trans- isomers of certain square planar platinum complexes. The reaction was discovered in 1893 by Russian chemist Nikolai Kurnakov and is still performed as an assay for compounds of this type. Safety The for thiourea is for rats (oral). A goitrogenic effect (enlargement of the thyroid gland) has been reported for chronic