Tellurophene
{{Chembox
| Name = Tellurophene
| ImageFile = Tellurophene.png
| ImageSize = 110 px
| ImageFileL1 = Tellurophene-3D-balls.png
| ImageFileR1 = Tellurophene-3D-vdW.png
| PIN = Tellurophene{{cite book |author=International Union of Pure and Applied Chemistry |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=The Royal Society of Chemistry |pages=883 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}
| OtherNames =
| Section1 = {{Chembox Identifiers
| ChemSpiderID = 119908
| PubChem = 136131
| CASNo = 288-08-4
| ChEBI = 30858
| Beilstein = 103225
| Gmelin = 647889
| StdInChI=1S/C4H4Te/c1-2-4-5-3-1/h1-4H
| StdInChIKey = TULWUZJYDBGXMY-UHFFFAOYSA-N
| SMILES = C1=C[Te]C=C1
}}
| Section2 = {{Chembox Properties
|C=4|H=4|Te=1
| MolarMass =
| RefractIndex = 1.6856
| Appearance = pale yellow
| Density = 2.13
| MeltingPtC = -36
| MeltingPt_notes =
| BoilingPtC = 148
| BoilingPt_notes = 714 mm Hg
| Solubility =
}}
| Section3 =
| Section4 =
| Section5 =
| Section6 =
}}
Tellurophene is the organotellurium compound with the formula {{chem2|C4H4Te}}. It is an analogue of single ring heterocyclic compounds thiophenes and selenophenes. It is a pale yellow liquid of some fundamental interest, especially as the parent of a number of substituted tellurophenes.
In 1966, Mack report a synthesis of an unsubstituted tellurophene through the reaction of sodium telluride with diacetylene in methanol. This method could be generalised to prepare 2,5-derivatives of tellurophene by selecting a suitably-substituted diacetylene precursor.{{Cite journal|last = Mack|first = W.|title = Synthesis of Tellurophene and its 2,5-Disubstituted Derivatives|journal = Angew. Chem. Int. Ed.|volume = 5|issue = 10|page = 896|doi = 10.1002/anie.196608961|year = 1966}} The product was obtained as a pale yellow liquid with a melting and boiling point of −36 °C and 148 °C, respectively. Taticchi et al. improved upon this synthesis by using a Schlenk line to exclude oxygen and moisture from the reaction vessel, using pure butadiyne (to decrease unwanted oxidation and polymerization side reactions), and by not using a vacuum to remove the methanol as it leads to loss of the product. This improved procedure allowed the tellurophene to be isolated in 47% yield.{{cite journal|title = Tellurophen and some of its derivatives|first1 = Francesco|last1 = Fringuelli|first2 = Aldo|last2 = Taticchi|journal = Journal of the Chemical Society, Perkin Transactions 1|doi = 10.1039/P19720000199|year = 1972|pages = 199–203}}
The geometry of tellurophene was first determined in 1973 through microwave spectroscopy, and has been further refined through X-ray diffraction studies.{{Cite journal|last1=Lukevics|first1=E.|last2=Arsenyan|first2=P.|last3=Belyakov|first3=S.|last4=Pudova|first4=O.|year=2002|title=Molecular Structure of Selenophenes and Tellurophenes|journal=Chemistry of Heterocyclic Compounds|volume=38|issue=7|pages=763–777|doi=10.1023/a:1020607300418|s2cid=92305752 |issn=0009-3122}} It has been found that the Te–C bond has a length of 2.046 Å, which is longer than that of selenophene. Further, the C–Te–C angle has been determined to be 82°, smaller than that found in selenophene, an observation attributed to the larger size of the tellurium atom. These findings are also consistent with the aromaticity of selenophene being greater than that of tellurophene; amongst its congeners, the order of decreasing aromaticity has been demonstrated to be: benzene > thiophene > selenophene > tellurophene > furan.{{cite book|series = Advances in Heterocyclic Chemistry|volume = 21|year = 1977|pages = 119–173|first1 = Francesco|last1 = Fringuelli|first2 = Gianlorenzo|last2 = Marino|first3 = Aldo|last3 = Taticchi| title=Advances in Heterocyclic Chemistry Volume 21 | chapter=Tellurophene and Related Compounds |doi = 10.1016/S0065-2725(08)60731-X|isbn = 9780120206216|chapter-url = https://books.google.com/books?id=1qIOmeTdiGcC&pg=PA119}}{{cite journal|title = A comparative study of the aromatic character of furan, thiophen, selenophen, and tellurophen|first1 = Francesco|last1 = Fringuelli|first2 = Gianlorenzo|last2 = Marino|first3 = Aldo|last3 = Taticchi|first4 = Giuliano|last4 = Grandolini|journal = Journal of the Chemical Society, Perkin Transactions 2|year = 1974|doi = 10.1039/P29740000332|volume = 1974|issue = 4|pages = 332–337}}
A variety of functionalized tellurophenes are known.{{Cite journal|last1=Karapala|first1=Vamsi Krishna|last2=Shih|first2=Hong-Pin|last3=Han|first3=Chien-Chung|year=2018|title=Cascade and Effective Syntheses of Functionalized Tellurophenes|journal=Organic Letters|volume=20|issue=6|pages=1550–1554|doi=10.1021/acs.orglett.8b00279|pmid=29494165|issn=1523-7060}}