Thiourea: Molecular Structure, Physical & Chemical Properties

Thiourea is an organosulfur compound (organic compounds that contain sulphur) with the formula SC(NH2)2. In other words, Thiourea is a sulphur analogue of Urea. It is structurally similar to Urea – an organic compound, except that the Oxygen atom is replaced by a sulphur atom, but the properties of Urea and Thiourea differ significantly.

It plays an important role in the construction of hetero-cycles, the compounds formed by the insertion of one or more, similar or different hetero-atoms (other than carbon or hydrogen atoms) in different cyclic systems. It appears as white crystals which are combustible and in contact with fire give off irritating or toxic fumes. It acts as a precursor to sulphide to produce metal sulphides like mercury sulphide.

Thiourea is a reagent in organic synthesis, a special branch of chemical synthesis, and is concerned with the construction of organic compounds via organic reactions. "Thioureas" can refer to a broad class of compounds with the general structure (R1R2N) (R3R4N) C=S.

Thiourea is also called by names such as “Thiocarbamide, and Pseudo thiourea”

Thioureas belong to thioamides, a functional group with the general structure R–CS–NR′R″, where R, R′, and R″ are organic groups. Examples include RC(S)NR2, where R is methyl, ethyl, etc.

Total global production of thiourea approximately 40% is produced in Germany and another 40% in China. About 10,000 tonnes of thiourea is being manufactured globally in a year. Its bulk production clearly proves its significance in the market. Few of its applications are listed below:

Thiourea Dioxide (prepared by oxidation of Thiourea with Hydrogen peroxide) is used as a reducing agent in many chemical reactions used in textile processing.

It is used in the production of flame-retardant resins, which prevents or slows down the spread of fires.

It is used as a source of sulphide, a compound of sulphur with another element. It reacts with alkyl halides and changes them into thiols, a sulphur analogue of alcohols that is simple it is an organic compound consisting of compounds with a sulphur atom. For example, ethane – 1,2 – dithiol is prepared by 1,2 – dibromoethane.

Thiourea can be used as a source of sulphide in reactions with metal ions as well. For example, mercury sulphide is formed when mercury ion reacts with thiourea in presence of water and heat

Thiourea condenses with - dicarbonyl and forms pyrimidine derivatives. It is used in vulcanization accelerators.

It is used as an auxiliary agent.

It is used in silver – gelatine photographic prints, diazo paper, light-sensitive photocopy paper, etc.

It is used in many electroplating processes such as Clifton – Philips and Beaver bright electroplating, etc.

For copper printed circuits, tin (II) chloride solution is used. Thiourea is also used in the solution.

It is used in silver cleaning products such as Tarn x which contains thiourea, sulfamic acid and detergent.

It is used in gold and silver leaching. Lixiviants are used for this purpose and thiourea is an important ingredient of these. Lixiviant is a liquid medium used in hydrometallurgy to selectively extract the desired metal from the ore or mineral.