THIOUREA

Thiourea is an organosulfur compound with the formula SC(NH2)2 and the structure H2N−C(=S)−NH2. 
Thiourea is structurally similar to urea (H2N−C(=O)−NH2), with the oxygen atom replaced by sulfur atom (as implied by the thio- prefix). 
The properties of urea and Thiourea differ significantly. 

CAS:    62-56-6
MF:    CH4N2S
MW:    76.12
EINECS:    200-543-5

Synonyms
Thiourea, reagent grade, ACS;Thiourea 5g [62-56-6];Thiourea(TU);AKOS BBS-00004390;SULFOUREA;THIO;THIOCARBAMIDE;THIOUREA DIOXID;THIOUREA;Thiocarbamide;62-56-6;2-Thiourea;Isothiourea;Pseudothiourea;Sulfourea;Thiuronium;Sulourea;2-Thiopseudourea;Carbamimidothioic acid;Thiocarbonic acid diamide;Urea, thio-;beta-Thiopseudourea;Thiomocovina;Urea, 2-thio-;Tsizp 34;Pseudourea, 2-thio-;Thioharnstoff;Thiokarbamid;USAF EK-497;carbonothioic diamide;Thiocarbamid;RCRA waste number U219;Sulfouren;Caswell No. 855;NSC 5033;CCRIS 588;aminothioamide;GYV9AM2QAG;thio-urea;UNII-GYV9AM2QAG;HSDB 1401;17356-08-0;aminothiocarboxamide;EINECS 200-543-5;H2NC(S)NH2;MFCD00008067;EPA Pesticide Chemical Code 080201;.beta.-Thiopseudourea;DTXSID9021348;CHEBI:36946;AI3-03582;NSC-5033;(NH2)2CS;CHEMBL260876;DTXCID101348;NSC5033;EC 200-543-5;THIOUREA (IARC);THIOUREA [IARC];TOU;Thiomocovina [Czech];sulfocarbamide;RCRA waste no. U219;CAS-62-56-6;S C (N H2)2;PROPYLTHIOURACIL IMPURITY A (EP IMPURITY);PROPYLTHIOURACIL IMPURITY A [EP IMPURITY];THIOUREA, ACS;thiopseudourea;2-Thio-Pseudourea;Thiocarbonic diamide;2-Thio-Urea;beta -thiopseudourea;Urea, 2-thio;Caswell no 855;THIOCARBMATE;Thiourea, 99%;Sulfourea;Thiocarbamide;thiourea; thiocarbamide;THIOUREA [HSDB];WLN: ZYZUS;THIOUREA[MI];THIOUREA [VANDF];Urea, thio- (8CI);THIOUREA [WHO-DD];Thiourea ACS Reagent Grade;Thiourea, LR, >=98%;MLS002454451;BIDD:ER0582;HMS2234E12;HMS3369M21;BCP27948;STR00054;Tox21_201873;Tox21_302767;BDBM50229993;STL194300;Thiourea, ACS reagent, >=99.0%;AKOS000269032;AKOS028109302;AT44959;CCG-207963;FT46947;UN 2877;Thiourea, ReagentPlus(R), >=99.0%;NCGC00091199-01;NCGC00091199-02;NCGC00091199-03;NCGC00256530-01;NCGC00259422-01;Thiourea, >=99.999% (metals basis);BP-31025;SMR000857187;Thiourea, JIS special grade, >=98.0%;Thiourea, p.a., ACS reagent, 99.0%;NS00002781;T0445;T2475;T2835;EN300-19634;10.14272/UMGDCJDMYOKAJW-UHFFFAOYSA-N.1;A833853;Q528995;Thiourea, puriss. p.a., ACS reagent, >=99.0%;doi:10.14272/UMGDCJDMYOKAJW-UHFFFAOYSA-N.1;F0001-1650;Thiourea, Pharmaceutical Secondary Standard; Certified Reference Material;200-543-5

Thiourea is a reagent in organic synthesis. 
Thioureas are a broad class of compounds with the formula SC(NHR)(NH2), SC(NHR)2, etc.
Thiourea appears as white crystal/powder, is combustible, and on contact with fire, gives off irritating or toxic fumes/gases. 
Thiourea is a reducing agent used primarily in the production of bleached recycled pulp. 
In addition, Thiourea is also effective in the bleaching of stone groundwood, pressurised groundwood. 
Thiourea undergoes decomposition on heating and produces toxic fumes of nitrogen oxides and sulphur oxides. 
Thiourea reacts violently with acrolein, strong acids, and strong oxidants. 
The main application of thiourea is in textile processing and also is commonly employed as a source of sulphide. 

Thiourea is a precursor to sulphide to produce metal sulphides, for example, mercury sulphide, upon reaction with the metal salt in aqueous solution. 
The industrial uses of thiourea include production of flame-retardant resins and vulcanisation accelerators. 
Thiourea is used as an auxiliary agent in diazo paper, light-sensitive photocopy paper, and almost all other types of copy paper. 
Thiourea is used in many industrial applications, including as a chemical intermediate or catalyst, in metal processing and plating, and in photoprocessing.
A colorless crystalline organic compound (the sulfur analog of urea). 
Thiourea is converted to the inorganic compound ammonium thiocyanate on heating. 
Thiourea is used as a sensitizer in photography and in medicine.
The simplest member of the thiourea class, consisting of urea with the oxygen atom substituted by sulfur.

Thiourea is the simplest member of the thiourea class, consisting of urea with the oxygen atom substituted by sulfur. 
Thiourea has a role as a chromophore and an antioxidant. 
Thiourea is a member of ureas, a member of thioureas and a one-carbon compound. 
Thiourea is functionally related to a carbonothioic O,O-acid and a urea.
Thiourea is the sulphur analogue of urea. 
Thiourea is used for its synthetic equivalence to hydrogen sulphide. 
Thiourea plays an important role in the construction of heterocycles. 
Thiourea appears as white crystals, which are combustible and, in contact with fire give off irritating or toxic fumes. 
Thiourea acts as a precursor to sulphide to produce metal sulphides like mercury sulphide.

Thiourea Chemical Properties
Melting point: 170-176 °C (lit.)
Boiling point: 263.89°C (estimate)
Density: 1.405
Bulk density: 640kg/m3
Refractive index: 1.5300 (estimate)
Storage temp.: Store below +30°C.
Solubility water: soluble137g/L at 20°C
Form: Crystals
Pka: -1.0(at 25℃)
Color: White to almost white
Specific Gravity: 1.406
PH: 6-8 (50g/l, H2O, 20℃)
Odor: Odorless
PH Range: 5 - 7
Water Solubility: 13.6 g/100 mL (20 ºC)
Merck: 14,9367
BRN: 605327
Stability: Stable. Incompatible with strong acids, strong bases, strong oxidizing agents, metallic salts, proteins, hydrocarbons. May react violently with acrolein.
InChIKey: UMGDCJDMYOKAJW-UHFFFAOYSA-N
LogP: -1.050 (est)
CAS DataBase Reference: 62-56-6(CAS DataBase Reference)
NIST Chemistry Reference: Thiourea(62-56-6)
IARC: 3 (Vol. Sup 7, 79) 2001
EPA Substance Registry System: Thiourea (62-56-6)

Structure and bonding
Thiourea is a planar molecule. 
The C=S bond distance is 1.71 Å. The C-N distances average 1.33 Å.
The weakening of the C-S bond by C-N pi-bonding is indicated by the short C=S bond in thiobenzophenone, which is 1.63 Å.
Thiourea occurs in two tautomeric forms, of which the thione form predominates in aqueous solutions. 
The equilibrium constant has been calculated as Keq is 1.04×10−3.
The thiol form, which is also known as an isothiourea, can be encountered in substituted compounds such as isothiouronium salts.

Production
The global annual production of thiourea is around 10,000 tonnes. 
About 40% is produced in Germany, another 40% in China, and 20% in Japan. 
Thiourea is manufactured by the reaction of hydrogen sulfide with calcium cyanamide in the presence of carbon dioxide.

CaCN2 + 3 H2S → Ca(SH)2 + (NH2)2CS
2 CaCN2 + Ca(SH)2 + 6 H2O → 2 (NH2)2CS + 3 Ca(OH)2
Ca(OH)2 + CO2 → CaCO3 + H2O

Applications
The most common uses for thiourea have been for the production of thiourea dioxide (30%), in leaching of gold and silver ores (25%), in diazo papers (15%), and as a catalyst in the synthesis of fumaric acid (10%) (IARC 2001). 
Thiourea has also been used in the production and modification of synthetic resins. 
Other uses of thiourea are as a photographic toning agent, in hair preparations, as a drycleaning agent, in the synthesis of pharmaceuticals and pesticides, in boiler-water treatment, and as a reagent for bismuth and selenite ions. 
Thiourea has also been used in textile and dyeing auxiliaries, in the production of industrial cleaning agents (e.g., for photographic tanks and metal surfaces in general), for engraving metal surfaces, as an isomerization catalyst in the conversion of maleic to fumaric acid, in copper-refining electrolysis, in electroplating, and as an antioxidant. 
Other uses have included as a vulcanization accelerator, an additive for slurry explosives,as a viscosity stabilizer for polymer solutions, and as a mobility buffer in petroleum extraction. 
Thiourea is also used as an ingredient of consumer silver polishes (HPD 2009), and has been used in the removal of mercury from wastewater by chlorine-alkali electrolysis.
Thiourea is used in the manufacture of resins,as a vulcanization accelerator, and as aphotographic fixing agent and to removestains from negatives.
Thiourea is wildly used in pharmaceutical industry, agricultural, chemicals, metallurgical industry, petroleum and so on. 
Thiourea is also main material for producing thiourea dioxide(CH1N2O2S).

In animal glue liquifiers and silver tarnish removers. 
Photographic fixing agent and to remove stains from negatives; manufacture of resins; vulcanization accelerator; a reagent for bismuth, selenite ions.
Thiourea is used in industries for the production of flame retardant resins and vulcanisation accelerators.
Used as a chemical intermediate or catalyst in metal processing and plating and in photo processing.
Used as a contaminant in the ethylene bisdithiocarbanate fungicides and can also be formed when food containing the fungicides is cooked.
Thiourea reacts with alkyl halides and gives isothiouronium salt on further hydrolysis reaction of this salt results in the formation of thiol and urea.

Production Methods    
Thiourea is formed by heating ammonium thiocyanate at 170 °C (338 °F). 
After about an hour, 25% conversion is achieved. 
With HCl, thiourea forms thiourea hydrochloride; with mercuric oxide, thiourea forms a salt; and with silver chloride, it forms a complex salt.

Thiox precursor
Thiourea per se has few applications. 
Thiourea is mainly consumed as a precursor to thiourea dioxide, which is a common reducing agent in textile processing.

Fertilizers
Recently thiourea has been investigated for its multiple desirable properties as a fertilizer especially under conditions of environmental stress.
Thiourea may be applied in various capacities, such as a seed pretreatment (for priming), foliar spray or medium supplementation.

Other uses
Other industrial uses of thiourea include production of flame retardant resins, and vulcanization accelerators. 
Thiourea is building blocks to pyrimidine derivatives. 
Thus, thioureas condense with β-dicarbonyl compounds.
The amino group on the thiourea initially condenses with a carbonyl, followed by cyclization and tautomerization. 
Desulfurization delivers the pyrimidine. 
The pharmaceuticals thiobarbituric acid and sulfathiazole are prepared using thiourea.
4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole is prepared by the reaction of thiourea and hydrazine.

Thiourea is used as an auxiliary agent in diazo paper, light-sensitive photocopy paper and almost all other types of copy paper.
Thiourea is also used to tone silver-gelatin photographic prints (see Sepia Toning).
Thiourea is used in the Clifton-Phillips and Beaver bright and semi-bright electroplating processes.
Thiourea is also used in a solution with tin(II) chloride as an electroless tin plating solution for copper printed circuit boards.
Thioureas are used (usually as hydrogen-bond donor catalysts) in a research theme called thiourea organocatalysis.
Thioureas are often found to be stronger hydrogen-bond donors (i.e., more acidic) than ureas.

Health Hazard    
The acute oral toxicity of thiourea in mostanimals is of low order. 
The oral LD50 values reported in the literature show variation.
Symptoms of chronic effects in rats includebone marrow depression and goiters. 
Administration of 32.8 mol of thiourea in chickembryos on day 17 of incubation resultedin the accumulation of parabronchial liquidin those embryos. 
The investigators have attributed such changes tothe toxic effects of thiourea, rather to than aretardation of pulmonary development.
Dedon and coworkers (1986) observed thepossible protective action of thiourea againstplatinum toxicity. 
Thiourea and other sulfur-containing nucleophiles have the ability tochelate and remove platinum from biochemical sites of toxicity.
Oral administration of thiourea resultedin tumors in the liver and thyroid in rats.
Thiourea is carcinogenic to animals and has shownsufficient evidence.

Biochem/physiol Actions    
Thiourea is a free radical scavenger of the peroxide radical. 
Thiourea was shown to inhibit lipid peroxidation and ultraviolet (UV)-induced crosslinking of collagen. 
Bud dormancy in plants can be inhibited by thiourea, which is used as a growth stimulator. 
Thiourea is also known to be used in the treatment of hyperthyroidism.