Thiourea (CHEM003847)

Thiourea is an organic compound of carbon, nitrogen, sulfur and hydrogen, with the formula CSN2H4 or (NH2)2CS. It is similar to urea, except that the oxygen atom is replaced by a sulfur atom. The properties of urea and thiourea differ significantly because of the relative electronegativities of sulfur and oxygen. Thiourea is a versatile 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 prohibited from use in food. Industrial uses of thiourea include production of flame retardant resins, and vulcanization accelerators. Thiourea is used as an auxiliary agent in diazo paper (light-sensitive photocopy paper) and almost all other types of copy paper. It is also used to tone silver-gelatin photographic prints. The liquid silver cleaning product TarnX is essentially a solution of thiourea. A leaching agent for gold leaching and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. Another common application for use of thiourea is a common sulfur source for making semiconductor cadmium sulfide nanoparticle. Thiourea is a planar molecule. The C=S bond distance is 1.60±0.1 for a wide range of derivatives. This narrow range indicates that the C=S bond is insensitive to the nature of the substitutent. Thus, the thioamide, which is similar to an amide group, is difficult to perturb. Thiourea reduces peroxides to the corresponding diols. The intermediate of the reaction is an unstable epidioxide which can only be identified at -100 °C. Epidioxide is similar to epoxide except with two oxygen atoms. This intermediate reduces to diol by thiourea. Thiourea has been shown to exhibit anti-viral, anti-fungal and radical scavenger functions (1, 2, 3).