- Thiourea
Chembox new
ImageFile=thiourea.png
ImageSize=
ImageFile2=Thiourea-3D-vdW.png
IUPACName=thiourea
OtherNames=
Section1= Chembox Identifiers
CASNo=62-56-6
PubChem=2723790
SMILES=C(=S)(N)N
Section2= Chembox Properties
Formula=CH4N2S
MolarMass=76.1219
Appearance=
Density=1.405 g/ml
MeltingPt=176-178℃
BoilingPt=
Solubility=95 at 10 °C
137 at 20 °C
Section3= Chembox Hazards
MainHazards=
FlashPt=
Autoignition=Thiourea is an
organic compound ofcarbon ,nitrogen ,sulfur andhydrogen , with the formula CSN2H4 or (NH2)2CS. It is similar tourea , except that theoxygen atom is replaced by asulfur atom. The properties of urea and thiourea differ significantly because of the relative electronegativities of sulfur and oxygen. Thiourea is a versatile reagent inorganic synthesis . "Thioureas" refers to a broad class of compounds with the general structure (R1R²N)(R³R4N)C=S. Thioureas are related tothioamide s, e.g. RC(S)NR2, where R ismethyl , ethyl, etc.tructure and bonding
Thiourea is a planar molecule. The C=S bond distance is 1.60±0.1 Å for a wide range of derivatives. This narrow range indicates that the C=S bond is insensitive to the nature of the substitutent. Thus, the thioamide, which is similar to an
amide group, is difficult to perturb.Thiourea occurs in two
tautomer ic forms::
ynthesis of thiourea
The global annual production of thiourea is around 10,000 tons. About 40% is produced in Germany, another 40% in China, and 20% in Japan.Thiourea can be prepared from
ammonium thiocyanate but more commonly is synthesized by the reaction ofhydrogen sulfide withcalcium cyanamide in the presence ofcarbon dioxide .Fact|date=September 2007Many thiourea derivatives are useful. "N,N"-unsubstituted thioureas are generally prepared by allowing the corresponding cyanamide to react with LiAlHSH in the presence of 1 N HCl in anhydrous
diethyl ether . LiAlHSH can be prepared by reactingsulfur withlithium aluminium hydride .Fact|date=September 2007Applications of thiourea
Thiourea reduces peroxides to the corresponding
diol s. [1] The intermediate of the reaction is an unstableepidioxide which can only be identified at -100 ℃. Epidioxide is similar toepoxide except with two oxygen atoms. This intermediate reduces to diol by thiourea.Thiourea is also used in the reductive workup of ozonolysis to give
carbonyl compounds. [2]Dimethyl sulfide is also an effective reagent for this reaction, but it is highly volatile (b.p. 37 ℃) and has an obnoxious odor whereas thiourea is odorless and conveniently non-volatile (reflecting its polarity).Thiourea is commonly employed to convert
alkyl halide s to thiols. Such reactions proceed via the intermediacy of isothiuronium salts. [3] . The reaction capitalizes on the high nuceophilicity of the sulfur center and the hydrolytic instability of the isothiuronium salt:::CS(NH2)2 + RX → RSC(NH2)2+X-::RSC(NH2)2+X- + 2 NaOH → RSNa + OC(NH2)2 + NaX::RSNa + HCl → RSH + NaClIn principle, alkali metal sulfides could also be used to convert alkyl halides to thiols, but thiourea avoids formation of dialkyl sulfides, a side product that plagues the use of Na2S and related reagents.Thioureas are used a building blocks to
pyrimidine derivatives. Thus thioureas condense with β-dicarbonyl compounds. [4] The amino group on the thiourea initially condenses with a carbonyl, followed by cyclization and tautomerization. Desulfurization delivers the pyrimidine.Similarly, aminothiazoles can be synthesized by the reaction of alpha-halo
ketone s and thiourea. [5]Another common application for use of thiourea is a common sulfur source for making
semiconductor cadmium sulfide nanoparticle. A slurry of 1 g cadmium sulfate (1.3 mmol), 0.5 g thiourea (6.6 mmol), and 0.1 g SiO2 (1.7 mmol) were sonicated for 3 hours under ambient air at room temperature. The colorless slurry solution changes to yellow indicating the generation of CdS.
Other industrial uses of thiourea include production offlame retardant resins, andvulcanization accelerators. Thiourea is used as an auxiliary agent in diazo paper (light-sensitivephotocopy paper) and almost all other types of copy paper. The liquid silver cleaning product TarnX is essentially a solution of thiourea. A leaching agent for gold leaching and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. [http://www.bnamericas.com/story.jsp?idioma=I§or=7¬icia=399641]afety
Thiourea is considered a possible human
carcinogen andmutagen according toDirective_67/548/EEC .Agoitrogen ic effect (enlargement of thethyroid gland ) has been reported, and hepatictumor s have resulted from chronic administration in rat. Bone marrow depression also has been reported.References
# C. Kaneko, A. Sugimoro, and S. Tanaka. A facile one-step synthesis of cis-2-cyclopentene and cis-2-cyclohexene-1,4-diols from the corresponding cyclodienes. “Synthesis”. 876, (1974).
# Gupta, D., Soman, G., and Dev, S.. Thiourea, a convenient reagent for the reductive cleavage of olefin ozonolysis products. “Tetrahedron”. 38, 3013 (1982)
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# Dodson, R. M., and King, L. C.. The reaction of ketones with halogens and thiourea. “J. Am. Chem. Soc.”, 67, 2242 (1945).
# The Chemistry of double-bonded functional groups edited by S. Patai. pp 1355-1496. John Wiley & Sons. New York, NY, 1977. ISBN 0-471-92493-8.External links
* [http://ptcl.chem.ox.ac.uk/MSDS/TH/thiourea.html MSDS on thiourea]
* [http://www.inchem.org/documents/cicads/cicads/cicad49.htm INCHEM assessment of thiourea]if thiourea is exposed it can cause a severe skin irritation.
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