:Thioureas

Thioureas have a trigonal planar molecular geometry of the {{chem2|N2C\dS}} core. The {{chem2|C\dS}} bond distance is near 1.71 Å, which is 0.1 Å longer than in normal ketones ({{chem2|R2C\dO}}). The C–N bond distances are short.{{cite journal|title=A Simple Refinement of Density Distributions of Bonding Electrons. IX. Bond Electron Density Distribution in Thiourea, C=S(NH₂)₂, at 123K|author1=D. Mullen |author2=E. Hellner |journal=Acta Crystallogr.|year=1978|volume=B34|issue=9|pages=2789–2794|doi=10.1107/S0567740878009243|doi-access=free}} Thioureas occurs in two tautomeric forms.

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On the other hand, some compounds depicted as isothioureas and in fact thioureas, one example being mercaptobenzimidazole.{{cite journal |doi=10.1107/S0567740876003026|title=The crystal and molecular structure of 2-mercaptobenzimidazole|year=1976|last1=Form|first1=G. R.|last2=Raper|first2=E. S.|last3=Downie|first3=T. C.|journal=Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry|volume=32|issue=2|pages=345–348}}

N,N′-unsubstituted thioureas can be prepared by treating the corresponding cyanamide with hydrogen sulfide or similar sulfide sources.{{cite journal | last1 = Koketsu | first1 = Mamoru | last2 = Kobayashi | first2 = Chikashi | last3 = Ishihara | first3 = Hideharu | title = Synthesis of N-aryl-S-alkylthiocarbamates | journal = Heteroatom Chemistry | volume = 14 | pages = 374–378 | year = 2003 | issue = 4 | doi = 10.1002/hc.10163}} Organic ammonium salts react with potassium thiocyanate as the source of the thiocarbonyl ({{chem2|C\dS}}).{{cite journal |last1 = Herr |first1 = R. J. |last2 = Kuhler |first2 = L. |last3 = Meckler |first3 = H. |last4 = Opalka |first4 = C. J. |year = 2000 |title = A Convenient Method for the Preparation of Primary and Symmetrical N,N′-Disubstituted Thioureas |journal = Synthesis |volume = 2000 |issue = 11 |pages = 1569–1574 |doi = 10.1055/s-2000-7607}}

Alternatively, N,N′-disubstituted thioureas can be prepared by coupling two amines with thiophosgene:{{cite journal|author=Yi-Bo Huang |author2=Wen-Bin Yi |author3=Chun Cai |title=Thiourea Based Fluorous Organocatalyst|journal=Topics in Current Chemistry|year=2012|volume=308|pages=191–212|doi=10.1007/128_2011_248|pmid=21972024|isbn=978-3-642-25233-4}}

:{{chem2|HNR2 + S\dCCl2 → 2 S\dC(NR2)2 + 2 HCl}}

Amines also condense with organic thiocyanates to give thioureas:{{cite journal|author1=Miyabe, H. |author2=Takemoto, Y. |title=Discovery and Application of Asymmetric Reaction by Multifunctional Thioureas|journal=Bull Chem Soc Jpn|year=2008|volume=81|issue=7|page=785|doi=10.1246/bcsj.81.785|doi-access=free}}

:{{chem2|HNR2 + S\dC\dNR' → S\dC(NR2)(NHR')}}

Cyclic thioureas are prepared by transamidation of thiourea with diamines. Ethylene thiourea is synthesized by treating ethylenediamine with carbon disulfide.{{cite journal |journal=Org. Syntheses| title = Ethylene Thiourea | author1 = C. F. H. Allen | author2 = C. O. Edens | author3 = James VanAllan | volume = 26 | page = 34 | doi = 10.15227/orgsyn.026.0034}} In some cases, thioureas can be prepared by thiation of ureas using phosphorus pentasulfide.

image:Ethylene thiourea.svg is an accelerant of vulcanization of neoprene and polychloroprene rubbers.]]

{{main|Thiourea#Reactions}}

Thioureas are susceptible to tautomerization. For the parent thiourea, the thione tautomer predominates in aqueous solutions.{{cite journal|last1=Allegretti|first1=P.E|last2=Castro|first2=E.A|last3=Furlong|first3=J.J.P|title=Tautomeric equilibrium of amides and related compounds: theoretical and spectral evidences|journal=Journal of Molecular Structure: THEOCHEM|date=March 2000|volume=499|issue=1–3|pages=121–126|doi=10.1016/S0166-1280(99)00294-8}} The thiol form, known as an isothiourea, can be encountered in substituted compounds such as isothiouronium salts.

Thioureas are nucleophilic at sulfur. When they contain a pair of N-H substituents, thioureas engage in hydrogen bonding. This interaction is the basis of a research theme called thiourea organocatalysis.{{cite journal|first=Peter |last=R. Schreiner |title=Metal-free organocatalysis through explicit hydrogen bonding interactions |journal=Chem. Soc. Rev. |date=2003 |volume=32 |issue=5 |pages=289–296 |doi=10.1039/b107298f |pmid=14518182}}Thioureas are often found to be stronger hydrogen-bond donors (i.e., more acidic) than ureas.{{cite journal |last1=Jakab |first1=Gergely |last2=Tancon |first2=Carlo |last3=Zhang |first3=Zhiguo |last4=Lippert |first4=Katharina M. |last5=Schreiner |first5=Peter R. |title=(Thio)urea Organocatalyst Equilibrium Acidities in DMSO |journal=Organic Letters |date=2012 |volume=14 |issue=7 |pages=1724–1727 |doi=10.1021/ol300307c|pmid=22435999}}{{cite journal |last1=Nieuwland |first1=Celine |last2=Fonseca Guerra |first2=Célia |title=How the Chalcogen Atom Size Dictates the Hydrogen-Bond Donor Capability of Carboxamides, Thioamides, and Selenoamides |journal=Chemistry – A European Journal |date=2022 |volume=28 |issue=31 |page=e202200755 |doi=10.1002/chem.202200755|pmid=35322485 |pmc=9324920}}

Agrichemicals that feature the thiourea functional group include diafenthiuron, methimazole, carbimazole (converted in vivo to methimazole), and propylthiouracil.{{cite journal |doi=10.1021/acs.jafc.5c00430 |title=Thiourea Derivatives in Agrochemical Discovery and Development |date=2025 |last1=Yi |first1=Qi-Qi |last2=Sun |first2=Ping |last3=Zhang |first3=Xinyi |last4=Wang |first4=Hao |last5=Wu |first5=Jian |journal=Journal of Agricultural and Food Chemistry |volume=73 |issue=15 |pages=8756–8774 |pmid=40190191 }} α-Naphthylthiourea is a commercial rodenticide.

Some thioureas are vulcanization accelerators.

Ergothioneine, which is derived from histidine, is a rare example of a thiourea found in nature.

The cyclic of thiourea called thiamazole is used to treat overactive thyroid

{{reflist|30em}}

• {{Cite book|title=The Chemistry of double-bonded functional groups |editor-first=S.|editor-last=Patai |pages=1355–1496 |publisher=John Wiley & Sons |location=New York, NY |date=1977 |isbn=0-471-92493-8}}

• [http://www.inchem.org/documents/cicads/cicads/cicad49.htm INCHEM assessment of thiourea]
• [http://www.inchem.org/documents/icsc/icsc/eics0680.htm International Chemical Safety Card 0680]

{{Thyroid hormone receptor modulators}}

Category:Functional groups