Thiourea, with the chemical formula SC(NH2)2, is an organosulfur compound that bears a close structural resemblance to urea (H2N−C(=O)−NH2), but with the oxygen atom replaced by a sulfur atom, as indicated by the prefix "thio-". Despite their similar structures, the properties of urea and thiourea differ markedly from each other.
Thiourea exists in two tautomeric forms in aqueous solutions, with the thione form being the more dominant one. The equilibrium constant for the conversion between the two forms has been calculated to be Keq=1.04×10-3. Substituted compounds, such as isothiouronium salts, contain the thiol form, which is also known as an isothiourea.
Thiourea itself has limited practical applications. Its primary use is as a precursor to thiourea dioxide, which is a widely used reducing agent in textile processing.
Thiourea is frequently utilized as a sulfide source in various chemical reactions, such as the conversion of alkyl halides to thiols. This reaction takes advantage of the sulfur center's high nucleophilicity and the intermediate isothiouronium salt's facile hydrolysis.
Thiourea finds numerous industrial applications, including the manufacture of flame-retardant resins and vulcanization accelerators. Additionally, it serves as an auxiliary agent in the production of diazo paper, light-sensitive photocopy paper, and almost all other kinds of copy paper.
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