Thiourea

Structural formula
General
Surname	Thiourea
other names	Thiocarbamide; Sulfourea; Sulfocarbamide; Thiourea; TH;
Molecular formula	C.H 4 N 2 S
Brief description	white odorless solid
External identifiers / databases
EC number	200-543-5
ECHA InfoCard	100,000,494
PubChem	2723790
Wikidata	Q528995
properties
Molar mass	76.12 g mol −1
Physical state	firmly
density	1.41 g cm −3 at 20 ° C
Melting point	176-178 ° C
boiling point	decomposition
solubility	sparingly soluble in water (137 g l −1 at 20 ° C)
safety instructions
H and P phrases	H: 302-351-361d-411
	P: 201-273-301 + 312 + 330-308 + 313-391-501
MAK	not fixed
Toxicological data	125 mg kg −1 ( LD 50 , rat , oral )
Thermodynamic properties
ΔH f 0	−89.1 kJ / mol
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Thiourea is a derivative of urea whose oxygen atom has been replaced by a sulfur atom.

Extraction and presentation

Thiourea can be obtained from ammonium thiocyanate , whereby the separation of product and starting material in the equilibrium reaction is difficult.

The technical synthesis takes place by introducing hydrogen sulfide and carbon dioxide into an aqueous suspension of calcium cyanamide .

{\ displaystyle \ mathrm {CaCN_ {2} +3 \, H_ {2} S \ rightarrow Ca (SH) _ {2} + (NH_ {2}) _ {2} CS}}

{\ displaystyle \ mathrm {2 \, CaCN_ {2} + Ca (SH) _ {2} +6 \, H_ {2} O \ rightarrow 2 \, (NH_ {2}) _ {2} CS + 3 \ , Ca (OH) _ {2}}}

{\ displaystyle \ mathrm {Ca (OH) _ {2} + CO_ {2} \ rightarrow CaCO_ {3} + H_ {2} O}}

properties

Physical Properties

Thiourea forms colorless and odorless crystals. The compound does not show a sharp melting point, since a rearrangement to ammonium thiocyanate takes place from 153 ° C. The literature gives melting points between 167 ° C and 182 ° C. At room temperature, thiourea has an orthorhombic crystal structure with space group Pnma (space group no. 62) . The carbon and sulfur atom lie on a mirror plane so that the molecule is the point group symmetry C _S has. It is almost planar and the symmetry is approximately C _2v . When the crystal cools or at high pressure, solid-solid phase transitions result in crystal structures with a different symmetry. Template: room group / 62

Chemical properties

Thiourea is an organic compound and a complexing agent . It occurs in two tautomeric forms . The thione form dominates in aqueous solutions:

Thione and thiol forms of thiourea

use

In 1993 the worldwide annual production was 10,000 tons. As a pure compound, thiourea is mainly used (25% of production) to extract metals such as gold and silver from ores . In addition, it is used as auxiliary substance in diazo paper (16% of production) and as a catalyst for isomerization of maleic acid in fumaric acid used (12% of production). As a reactant , thiourea is mainly used in the production of thiourea dioxide (27.5% of production.) Other important applications are:

As a gloss additive in galvanic baths

In analysis for the detection of bismuth (yellow color in nitric acid solution)

Additive in explosives ( blasting sludge )

Metal finishing (copper finishing)

Metal cleaning ( silver cleaning )

Modification of resins

Manufacture of auxiliary materials for the textile and paint industry

Manufacture of chemical intermediates

Conversion to thiobarbiturates ( barbiturates , drugs such as thiopental ) using diethylmalonic acid ester derivatives
Separation of n -alkanes and iso- alkanes in urea extractive crystallization

Biological importance

Thiourea can inhibit the enzymes tyrosinase and urease .

safety instructions

Thiourea is carcinogenic category 3 (possibly carcinogenic to humans) and teratogenic Category 3 (possibly teratogenic in humans) .- It can be very difficult to remove with normal waste water treatment methods from wastewater.

Derived connections

Web links

Commons : Thiourea - collection of images, videos and audio files

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Entry on thiourea in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
↑ Entry on thiourea in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.
↑ ^a ^b ^c ^d Mertschenk, B .; Knott, A .; Bauer, W .: Thiourea and Thiourea Derivatives , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a26_803.pub3 .
↑ MR Truter: Comparison of photographic and counter observations for the X-ray crystal structure analysis of thiourea . In: Acta Crystallographica . tape 22 , no. 4 , 1967, p. 556-559 , doi : 10.1107 / S0365110X67001124 .
↑ I. Takahashi, A. Onodera, Y. Shiozaki: Structural changes of thiourea in connection with its phase transitions: reappraisal of rigidity and libration of the molecule . In: Acta Crystallographica Section B . tape 46 , no. 5 , 1990, pp. 661-664 , doi : 10.1107 / S0108768190006012 .
↑ T. Asahi, K. Hasebe, A. Onodera: Crystal Structure of the High Pressure Phase VI of Thiourea . In: Journal of the Physical Society of Japan . tape 69 , 2000, pp. 2895-2899 , doi : 10.1143 / JPSJ.69.2895 .
^ ^A ^b ^c ^d ^e ^f ^g Concise International Chemical Assessment Document (CICAD) for Thiourea , accessed December 9, 2014.
↑ Herwig Hulpke, Herbert A. Koch, Reinhard Nießner: RÖMPP Lexicon Environment, 2nd edition, 2000 . Georg Thieme Verlag, 2014, ISBN 3-13-179342-2 , p. 795 ( limited preview in Google Book search).
^ Ullmanns Encyclopedia : Ullmanns Enzyklopädie der technischen Chemie , Wiley Verlag.
↑ Jander / Blasius: Textbook of analytical and preparative inorganic chemistry , S. Hirzel-Verlag Stuttgart, 1985.
^ Friedrich Asinger : Chemistry and technology of paraffin hydrocarbons . Akademie Verlag, 1956, pp. 53–59.

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Entry on thiourea in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

[CLP_100.000.494-2] Entry on thiourea in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[CRC90_5_20-3] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.

[Ullmann-4] Mertschenk, B .; Knott, A .; Bauer, W .: Thiourea and Thiourea Derivatives , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a26_803.pub3 .

[5] MR Truter: Comparison of photographic and counter observations for the X-ray crystal structure analysis of thiourea . In: Acta Crystallographica . tape 22 , no. 4 , 1967, p. 556-559 , doi : 10.1107 / S0365110X67001124 .

[6] I. Takahashi, A. Onodera, Y. Shiozaki: Structural changes of thiourea in connection with its phase transitions: reappraisal of rigidity and libration of the molecule . In: Acta Crystallographica Section B . tape 46 , no. 5 , 1990, pp. 661-664 , doi : 10.1107 / S0108768190006012 .

[7] T. Asahi, K. Hasebe, A. Onodera: Crystal Structure of the High Pressure Phase VI of Thiourea . In: Journal of the Physical Society of Japan . tape 69 , 2000, pp. 2895-2899 , doi : 10.1143 / JPSJ.69.2895 .

[WHO-8] A ^b ^c ^d ^e ^f ^g Concise International Chemical Assessment Document (CICAD) for Thiourea , accessed December 9, 2014.

[Herwig_Hulpke,_Herbert_A._Koch,_Reinhard_Nießner-9] Herwig Hulpke, Herbert A. Koch, Reinhard Nießner: RÖMPP Lexicon Environment, 2nd edition, 2000 . Georg Thieme Verlag, 2014, ISBN 3-13-179342-2 , p. 795 ( limited preview in Google Book search).

[UllmannsEnzyklopädie-10] Ullmanns Encyclopedia : Ullmanns Enzyklopädie der technischen Chemie , Wiley Verlag.

[JanderBlasius-11] Jander / Blasius: Textbook of analytical and preparative inorganic chemistry , S. Hirzel-Verlag Stuttgart, 1985.

[asinger-12] Friedrich Asinger : Chemistry and technology of paraffin hydrocarbons . Akademie Verlag, 1956, pp. 53–59.