In
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...
, thioureas are members of a family of
organosulfur compound
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfu ...
s with the
formula
In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...
and
structure
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
. The
parent member of this class of compounds is
thiourea
Thiourea () is an organosulfur compound with the formula and the structure . It is structurally similar to urea (), except that the oxygen atom is replaced by a sulfur atom (as implied by the ''thio-'' prefix); however, the properties of urea ...
(). The thiourea
functional group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...
has a
planar
Planar is an adjective meaning "relating to a plane (geometry)".
Planar may also refer to:
Science and technology
* Planar (computer graphics), computer graphics pixel information from several bitplanes
* Planar (transmission line technologies), ...
core.
Structure and bonding
Thioureas have planar core. The
bond distance
In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest of ...
is near 1.71
Å, which is 0.1 Å longer than in normal
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s (). The
C–N bond distances are short. Thioureas occurs in two
tautomer
Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert.
The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hydr ...
ic forms. For the parent thiourea, the thione form predominates in aqueous solutions. The thiol form, known as an isothiourea, can be encountered in substituted compounds such as
isothiouronium
In organic chemistry, isothiouronium is a functional group with the formula SC(NH2)2sup>+ (R = alkyl, aryl) and is the acid salt of isothiourea. The H centres can also be replaced by alkyl and aryl. Structurally, these cations resemble guanidi ...
salts.
:
Synthesis
''N'',''N''′-unsubstituted thioureas can be prepared by treating the corresponding
cyanamide
Cyanamide is an organic compound with the chemical formula, formula carbon, Cnitrogen, N2hydrogen, H2. This white solid is widely used in agriculture and the production of pharmaceuticals and other organic compounds. It is also used as an alcoho ...
with
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
or similar sulfide sources. Organic ammonium salts react with
potassium thiocyanate
Potassium thiocyanate is the chemical compound with the molecular formula KSCN. It is an important salt of the thiocyanate anion, one of the pseudohalides. The compound has a low melting point relative to most other inorganic salts.
Use in chem ...
as the source of the
thiocarbonyl
In organic chemistry, thioketones (; also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structu ...
().
Alternatively, ''N'',''N''′-disubstituted thioureas can be prepared by coupling two
amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...
s with
thiophosgene
Thiophosgene is a red liquid with the formula . It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses.
Preparation
is prepared in a two-step process from carbon ...
:
:
2 HNR2 + Cl2S=C -> 2 S=C(NR2)2 + 2 HCl
Amines also condense with organic
thiocyanates
Thiocyanate (also known as rhodanide) is the anion . It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyrot ...
to give thioureas:
:
HNR2 + S=C=NR' -> S=C(NR2)(NHR')
Cyclic thioureas are prepared by
transamidation Transamidation is a chemical reaction in which an amide reacts with an amine to generate a new amide:
:RC(O)NR'2 + HNR"2 → RC(O)NR"2 + HNR'2
The reaction is typically very slow, but it can be accelerated with Lewis acid and organometallic ...
of thiourea with diamines.
Ethylene thiourea
Ethylene thiourea (ETU) is an organosulfur compound with the formula . It is an example of an ''N'',''N''-disubstituted thiourea. It is a white solid. It is synthesized by treating ethylenediamine with carbon disulfide.
Ethylene thioureas are an ...
is synthesized by treating
ethylenediamine
Ethylenediamine (abbreviated as en when a ligand) is the organic compound with the formula C2H4(NH2)2. This colorless liquid with an ammonia-like odor is a basic amine. It is a widely used building block in chemical synthesis, with approximately ...
with
carbon disulfide
Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non ...
. In some cases, thioureas can be prepared by thiation of ureas using
phosphorus pentasulfide
Phosphorus pentasulfide is the inorganic compound with the formula (monomer) or (dimer). This yellow solid is the one of two phosphorus sulfides of commercial value. Samples often appear greenish-gray due to impurities. It is soluble in carbon d ...
.
138px, is an excellent Accelerant#Rubber vulcanization">accelerant
Accelerants are substances that can bond, mix or disturb another substance and cause an increase in the speed of a natural, or artificial chemical process. Accelerants play a major role in chemistry—most chemical reactions can be hastened with an ...
of vulcanization of neoprene and polychloroprene rubbers.
Applications
Precursor to heterocycles
Thioureas are 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
Thiobarbituric acid is an organic compound and a heterocycle. It is used as a reagent in assaying malondialdehyde
Malondialdehyde (MDA) is the organic compound with the nominal formula CH2(CHO)2. A colorless liquid, malondialdehyde is a highly r ...
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
Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...
.
Catalysis
Some thioureas are
vulcanization
Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to include ...
accelerators. Thioureas are also used in a research theme called
thiourea organocatalysis
Within the area of organocatalysis, (thio)urea organocatalysis describes the use of ureas and thioureas to accelerate and stereochemically alter organic transformations. The effects arise through hydrogen-bonding interactions between the substrate ...
.
References
Further reading
*
External links
INCHEM assessment of thiourea
{{Thyroid hormone receptor modulators
Functional groups