Thiourea

What is Thiourea?

An organosulfur compound composed of carbon, nitrogen, hydrogen and sulfur atoms. Its chemical formula is SC(NH2)2. As the name and its composition suggests, thiourea is very much similar to urea. In thiourea, the oxygen atom of urea is displaced by sulfur atom. Here you need to note that urea and thiourea are structurally similar but very different in physical and chemical properties. Thiourea is also known as thiocarbamide.


All hydrogen atoms of thiourea can be substituted by alkyl group and thus formed compounds come under the category of the class thioureas. Such compounds have the general formula (R1R2N) (R3R4N) C=S, where R is an alkyl group. 


Formula of Thiourea 

IUPAC Name - Thiourea 

Empirical Formula 

CH4N2S

Molecular Formula

CH4N2S or SC(NH2)2  (extended molecular formula)

Structural Formula 

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Thioureas is a class of thiourea compounds with the general formula (R1R2N)(R3R4N)C=S. Its general structural formula is given below –

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General chemical structure of a compound of class thioureas(image will be uploaded soon)


Structure of Thiourea 

It is found in its two tautomeric forms – thione form and thiol form. Thione form is found in larger amounts in aqueous solutions. It’s both tautomeric forms are given below –

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Its thiol form is also known as isothiourea. 

Thiourea has planar structure. It is a covalent compound. It has a double bond between carbon and sulfur. C=S bond distance in thiourea is 1.71 A and average of C-N distances is 1.33 A

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Properties of Thiourea 

Physical and Chemical properties – Thiourea shows following physical and chemical properties –

  • It is an organosulfur compound. 

  • Its molar mass is 76.12 g.mol-1.

  • It is a white colored compound.

  • It is found as solid at room temperature. 

  • Melting point of thiourea is 182 .

  • Its boiling point is 155 .

  • Its density is 1.405 g.ml-1.

  • It is highly soluble in water. 142g of thiourea can be dissolved in one liter of water at 25 .

  • It is weakly acidic in nature.

  • Its crystals are combustible on contact with fire. 

  • Its pH is more than 3. 

  • It is an odorless compound.

  • Its surface tension is 1.04 10-2 N/m.

  • Conversion in ammonium thiocyanate – Thiourea on heating above 130 , forms ammonium thiocyanate. Although upon cooling its again converts into thiourea. Reaction is given below –

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  • Reduction – Peroxides get reduced into their corresponding diols by thiourea. During this reduction reaction an intermediate is formed which is called endoperoxide. Endoperoxide is a highly unstable compound. Reaction is given below –

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  • Due to its non - volatile nature, it is also used in ozonolysis of cyclic alkenes to give carbonyl compounds. Reaction is given below –

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  • It reacts with alkyl halides and forms thiols. 


Production of Thiourea 

Thiourea can be prepared by ammonium thiocyanate. On heating ammonium thiocyanate, it forms thiourea. Reaction is given below –

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It’s a reversible reaction and gives high yield at a specific temperature only. So, it is not used commonly for production of thiourea. Most commonly calcium cyanamide is used for production of thiourea. Hydrogen sulfide reacts with calcium cyanamide in presence of carbon dioxide and forms thiourea. 


Uses of Thiourea 

Total global production of thiourea approximately 40% is produced in Germany and another 40% in China. Thus, Germany and China are the main manufacturers of thiourea. Approximately 10,000 tonnes of thiourea is being produced globally in a year. Its huge production clearly states its importance in the market. Few of its applications are listed below –

  • It is mainly used as a precursor to thiourea dioxide. Thiourea dioxide is used as a reducing agent in many chemical reactions used in textile processing. 

  • It is used in production of flame - retardant resins. 

  • It is used as a source of sulfide. It reacts with alkyl halides and changes them into thiols. For example, ethane – 1,2 – dithiol is prepared by 1,2 – dibromoethane. Reaction is given below –

C2H4Br2 + 2SC(NH2)2 → [C2H4(SC(NH2)2)2]Br2

[C2H4(SC(NH2)2)2]Br2 + 2KOH → C2H4(SH)2 + 2OC(NH2)2 + 2KBr

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

Hg2+ + SC(NH2)2 + H2O → HgS + OC(NH2)2 + 2H+

  • Pyrimidine derivatives are formed by using thiourea. Thiourea condense with - dicarbonyl and forms pyrimidine derivatives. Reaction is given below –

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  • It is used in vulcanization accelerators. 

  • It is used as an auxiliary agent. 

  • It is used in silver – gelatin photographic prints.

  • It is used in 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 TarnX. TarnX 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. 


Health Hazards from Thiourea 

Even short exposure of the thiourea can cause irritation and temporary skin infection. 125mg/kg of thiourea can be lethal for rats on oral ingestion. On chronic exposure, thiourea can cause a goitrogenic effect on humans. Enlargement of thyroid gland is known as goiter disease. In this disease goitrogens disrupt the production of thyroid hormones. This stimulates the pituitary gland to release TSH and TSH promotes the growth of thyroid tissues. Over exposure of thiourea may have adverse health effects. It can be poisonous as well.


This ends our coverage on the topic “Thiourea”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions of NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.