Thiourea

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Thiourea

Thiourea is an organic compound

Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
of carbon

Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
, sulfur

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
and hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, with the formula

Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
C

Carbon

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
N

Nitrogen

Hydrogen

Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
)₂C

Carbon

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
. It is similar to urea

Urea

Urea is an organic compound with the chemical formula 2carbonoxygen.Urea is also known by the International Nonproprietary Name carbamide, as established by the World Health Organization....
, except that the oxygen

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
atom is replaced by a sulfur

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
atom. The properties of urea and thiourea differ significantly because of the relative electronegativities of sulfur and oxygen. Thiourea is a versatile reagent in organic synthesis

Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic_chemistry molecules can often contain a higher level of complexity compared to purely Inorganic_chemistry compounds, so the synthesis of organic compounds has developed into one of the most im...
. "Thioureas" refers to a broad class of compounds with the general structure (R¹R²N)(R³R⁴N)C=S.

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Encyclopedia

Thiourea is an organic compound

Organic compound

Carbon

Nitrogen

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
and hydrogen

Hydrogen

Chemical formula

Carbon

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
N

Nitrogen

Hydrogen

Amine

Carbon

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
. It is similar to urea

Urea

Oxygen

Sulfur

Organic synthesis

Thioamide

Thioamide is a functional group with the general structure R-CS-NR'R, where R, R', and R are organic groups. They are analogous to amides but they exhibit greater multiple bond character along the C-N bond, resulting in a larger rotational barrier....
s, e.g. RC(S)NR₂, where R is methyl, ethyl

Ethyl group

In chemistry, an ethyl group is an alkyl functional group derived from ethane . It has the chemical formula -Carbon2Hydrogen5 and is very often abbreviated -Et....
, etc.

Structure 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

Amide

In chemistry, an amide is one of three kinds of compounds:* the organic chemistry functional group characterized by a carbonyl group linked to a nitrogen atom , or a compound that contains this functional group ; or...
group, is difficult to perturb.

Thiourea occurs in two tautomer

Tautomer

Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. Commonly this reaction results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond....
ic forms:

Synthesis 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 of hydrogen sulfide

Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence....
with calcium cyanamide

Calcium cyanamide

Calcium cyanamide or CaCN2 is a calcium compound used as fertiliser, first synthesized in 1898 by Adolph Frank and Nikodem Caro....
in the presence of carbon dioxide

Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
.

Many 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

Diethyl ether

Diethyl ether, also known as ether and ethoxyethane, is a clear, colorless, and highly flammable liquid with a low boiling point and a characteristic odor....
. LiAlHSH can be prepared by reacting sulfur

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
with lithium aluminium hydride

Lithium aluminium hydride

Lithium aluminium hydride , commonly abbreviated to LAH, is a reducing agent used in organic synthesis. It is more powerful than the related reagent sodium borohydride due to the weaker Al-H bond compared to the B-H bond....
.

Applications of thiourea

Thiourea reduces peroxides to the corresponding diol

Diol

A diol or glycol is a chemical compound containing two hydroxyl groups Vicinal diols have hydroxyl groups attached to adjacent atoms. Examples of vicinal diol compounds are ethylene glycol and propylene glycol....
s. The intermediate of the reaction is an unstable epidioxide which can only be identified at -100 °C. Epidioxide is similar to epoxide

Epoxide

An epoxide is a cyclic ether with only three ring atoms. This ring approximately is an equilateral triangle which makes it highly ring strain....
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

Carbonyl

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double bond to an oxygen atom : C=O.The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex ; in this situation, carbon is triple-bonded to oxygen : C=O....
compounds. Dimethyl sulfide

Dimethyl sulfide

Dimethyl sulfide or methylthiomethane is an Organosulfur compounds compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at 37?C and has a characteristic disagreeable odor....
is also an effective reagent for this reaction, but it is highly volatile (b.p. 37 °C) and has an obnoxious odor whereas thiourea is odorless and conveniently non-volatile (reflecting its polarity).

Thiourea is commonly employed to convert alkyl halides to thiols. Such reactions proceed via the intermediacy of isothiuronium salts. 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 + NaCl In 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

Pyrimidine

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring....
derivatives. Thus thioureas condense with ß-dicarbonyl compounds. 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

Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
s and thiourea.

Another common application for use of thiourea is a common sulfur source for making semiconductor

Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
cadmium sulfide

Cadmium sulfide

Cadmium Sulfur is a chemical compound with the formula CdS. Cadmium sulfide is yellow in colour and is a semiconductor. It exists in nature as two different minerals, greenockite and hawleyite....
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 of flame retardant

Flame retardant

Flame retardants are materials that inhibit or resist the spread of fire. These can be separated into several categories:*Minerals such as asbestos, compounds such as aluminium hydroxide, magnesium hydroxide, antimony trioxide, various hydrates, red phosphorus, and boron compounds, mostly borates....
resins, and vulcanization

Vulcanization

Vulcanization refers to a specific curing process of rubber involving high heat and the addition of sulfur or other equivalent curatives. It is a chemical process in which polymer molecules are linked to other polymer molecules by atomic bridges composed of sulfur atoms or carbon to carbon bonds....
accelerators. Thiourea is used as an auxiliary agent in diazo paper (light-sensitive photocopy 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.

Safety

Thiourea is considered a possible human carcinogen

Carcinogen

The term carcinogen refers to any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation....
and mutagen

Mutagen

In biology, a mutagen is a physical or chemical agent that changes the genetic information of an organism and thus increases the frequency of mutations above the natural background level....
according to Directive 67/548/EEC

Directive 67/548/EEC

The Dangerous Substances Directive is one of the main European Union laws concerning chemical safety. It was made under Article 100 of the Treaty of Rome....
. A goitrogen

Goitrogen

Goitrogens are substances that suppress the function of the thyroid gland by interfering with iodine uptake which can, as a result, cause an enlargement of the thyroid, i.e....
ic effect (enlargement of the thyroid gland) has been reported, and hepatic tumor

Tumor

A tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells . Tumor is not synonymous with cancer. A tumor can be Benign neoplasm, Carcinoma in situ or malignant, whereas cancer is by definition malignant....
s have resulted from chronic administration in rat. Bone marrow depression also has been reported.

Thiourea

Structure and bonding

Synthesis of thiourea

Applications of thiourea

Safety

Further reading

External links