Thiourea
[CAS# 62-56-6]

Identification

• Classification: Organic raw materials >> Organic sulfur compound
• Name: Thiourea
• Synonyms: Thiocarbamide
• Molecular Formula: CH₄N₂S
• Molecular Weight: 76.12
• CAS Registry Number: 62-56-6
• EC Number: 200-543-5
• SMILES: C(=S)(N)N

Properties

• Density: 1.5±0.1 g/cm³ Calc.^*, 1.405 g/mL (Expl.)
• Melting point: 170 - 176 °C (Expl.)
• Boiling point: 98.4±23.0 °C 760 mmHg (Calc.)^*
• Flash point: 13.3±22.6 °C (Calc.)^*
• Index of refraction: 1.656 (Calc.)^*
• Water solubility: 13.6 g/100 mL (20 °C)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07;GHS08;GHS09 Warning
• Risk Statements: H302-H351-H361-H361d-H411
• Safety Statements: P203-P264-P270-P273-P280-P301+P317-P318-P330-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Carcinogenicity	Carc.	2	H351
Acute toxicity	Acute Tox.	4	H302
Reproductive toxicity	Repr.	2	H361
Reproductive toxicity	Repr.	2	H361d
Skin sensitization	Skin Sens.	1	H317
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	3	H301
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	3	H331
Reproductive toxicity	Repr.	2	H361d

• Transport Information: UN 2877; UN 2811

Discovery and Applications

Thiourea is a sulfur-containing organic compound with the formula SC(NH₂)₂. It was first synthesized in the 19th century and has been extensively studied for its chemical and industrial properties. Thiourea is a white crystalline solid that is soluble in water and many polar organic solvents.

Thiourea’s discovery dates back to the early development of organic sulfur chemistry, with its structure established through chemical and spectroscopic analyses over time. It is structurally similar to urea, but with the oxygen atom replaced by sulfur, which imparts distinct chemical behavior.

Thiourea is widely used in various industrial and laboratory applications. It serves as an important reagent in organic synthesis, particularly in the preparation of thiourea derivatives, thioamides, and heterocyclic compounds such as thiadiazoles and thiazoles. These derivatives find use in pharmaceuticals, agrochemicals, and dyes.

One significant application of thiourea is in photographic fixing and processing. It acts as a reducing agent to remove unreacted silver halides from photographic films and papers, thereby stabilizing the image. Its ability to complex with metals also makes it useful in electroplating and metal polishing processes.

Thiourea is employed in the textile industry as a vulcanization accelerator in rubber production and as a stabilizer in the manufacture of plastics and resins. Its chemical properties allow it to interact with polymers, enhancing mechanical and thermal properties.

In agriculture, thiourea is used as a plant growth regulator. It can influence germination, flowering, and stress resistance in various crops, although its use is controlled due to potential toxicity.

Thiourea is also a valuable analytical reagent. It forms complexes with metal ions, enabling qualitative and quantitative determination of metals in chemical analysis. Its reactivity with aldehydes and ketones is exploited in organic chemistry for the synthesis of diverse compounds.

From a safety perspective, thiourea has moderate toxicity and should be handled with care. It is classified as a potential carcinogen and irritant. Proper protective measures and regulatory limits govern its use in industrial and laboratory settings.

In summary, thiourea is a well-established sulfur-containing compound discovered in the 19th century, extensively utilized in organic synthesis, photography, metal processing, rubber vulcanization, and agriculture. Its versatile chemical reactivity and ability to form metal complexes underpin its broad applications, while safety considerations guide its handling and use.

References

1888. Ü ber die Einwirkung der Aldehyde auf Rhodanammonium. Monatshefte für Chemie und verwandte Teile anderer Wissenschaften, 9(1).
DOI: 10.1007/bf01510020

2014. Isosteric Substitutions of Urea to Thiourea and Selenourea in Aliphatic Oligourea Foldamers: Site‐Specific Perturbation of the Helix Geometry. Chemistry (Weinheim an der Bergstrasse, Germany), 21(5).
DOI: 10.1002/chem.201405792

2016. Synthesis and biological evaluation of fluoropyrazolesulfonylurea and thiourea derivatives as possible antidiabetic agents. Journal of Enzyme Inhibition and Medicinal Chemistry, 31(6).
DOI: 10.1080/14756366.2016.1180594