Furano: Diferenzas entre revisións
Contido eliminado Contido engadido
Miguelferig moveu a páxina "Furano" a "Furano, Xapón": hai homonimia con outros termos de máis uso. |
traducido de en:Furan |
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{{Chembox
| Watchedfields = changed
| verifiedrevid = 477167468
| ImageFileL1 = Furan-2D-full.svg
| ImageNameL1 = Fórmula estrutural do furano
| ImageFileR1_Ref =
| ImageFileR1 = Furan-2D-numbered.svg
| ImageNameR1 = fórmula esquelética con numeración
| ImageFileL2 = Furan-CRC-MW-3D-balls-A.png
| ImageNameL2 = modelo de bólas e paus
| ImageFileR2 = Furan-CRC-MW-3D-vdW.png
| ImageNameR2 = modelo de recheo de espazos
| IUPACName = Furano
| SystematicName = Oxol<br />5-Oxaciclopenta-1,3-dieno<br />5-Oxaciclo-1,3-pentadieno<br />1,4-Epoxibuta-1,3-dieno<br/>1,4-Epoxi-1,3-butadieno
| OtherNames = Furfurán<br />Furán<br />Divinileno óxido
|Section1={{Chembox Identifiers
| KEGG_Ref =
| KEGG = C14275
| InChI = 1/C4H4O/c1-2-4-5-3-1/h1-4H
| InChIKey = YLQBMQCUIZJEEH-UHFFFAOYAC
| ChEMBL_Ref =
| ChEMBL = 278980
| StdInChI_Ref =
| StdInChI = 1S/C4H4O/c1-2-4-5-3-1/h1-4H
| StdInChIKey_Ref =
| StdInChIKey = YLQBMQCUIZJEEH-UHFFFAOYSA-N
| CASNo_Ref =
| CASNo = 110-00-9
| PubChem = 8029
| ChemSpiderID_Ref =
| ChemSpiderID = 7738
| ChEBI_Ref =
| ChEBI = 35559
| SMILES = c1ccoc1
}}
|Section2={{Chembox Properties
| C=4 | H=4 | O=1
| Appearance = Incoloro, líquido volátil
| Density = 0,936 g/mL
| MeltingPtC = −85,6
| BoilingPtC = 31,3
| Solubility =
}}
|Section3={{Chembox Hazards
| MainHazards =
| FlashPtC = −69
| AutoignitionPtC = 390
| ExploLimits = Inferior:2,3%, superior:14.3% @ 20 °C
| NFPA-H = 3
| NFPA-F = 4
| NFPA-R = 1
| RPhrases = {{R26/27/28}}, {{R45}}
| SPhrases = {{S16}}, {{S37}}, {{S45}}, {{S28}}
| LD50 = > 2 g/kg (rata)
| ExternalSDS = [http://www.pennakem.com/msds/110-00-9_Furan_PAK_msds.pdf Pennakem]
}}
|Section4={{Chembox Related
| OtherFunction = [[Pirrol]]<br />[[Tiofeno]]
| OtherFunction_label = [[heterociclo]]s
| OtherCompounds = [[Tetrahidrofurano]] (THF)<br />[[2,5-Dimetilfurano]]<br />[[Benzofurano]]<br />[[Dibenzofurano]]
}}
|Section5={{Chembox Structure
| CrystalStruct =
| PointGroup = C<sub>2v</sub>
}}
}}
O '''furano''' é un [[composto heterocíclico]] [[composto orgánico|orgánico]], que consta dun anel [[aromaticidade|aromático]] de cinco membros con catro átomos de carbono e un de oxíxeno. A clase de compostos que conteñen eses aneis tamén se denominan furanos.
O furano é un líquido incoloro, inflamable, moi volátil cun [[punto de ebulición]] próximo á temperatura ambiente dunha habitación. É soluble en solventes orgánicos comúns, como o [[alcohol]], [[éter]], e [[acetona]], pero é lixeriramenrte soluble en [[auga]].<ref>{{cite book | author = Hans Dieter Jakubke | author2 = Hans Jeschkeit | title = Concise Encyclopedia of Chemistry | publisher = Walter de Gruyter | isbn = 0-89925-457-8| pages = 001–1201 | year = 1994}}</ref> É un composto [[tóxico]] e pode ser [[carcinóxeno]] para os humanos. O furano utilízase como material inicial para a obtención de compostos químicos especializados.<ref name="ullmann" />
== Historia ==
<!--
The name ''furan'' comes from the Latin ''furfur'', which means [[bran]].<ref>Alexander Senning. ''Elsevier's Dictionary of Chemoetymology''. Elsevier, '''2006'''. ISBN 0-444-52239-5.</ref> The first furan derivative to be described was [[2-furoic acid]], by [[Carl Wilhelm Scheele]] in 1780. Another important derivative, [[furfural]], was reported by [[Johann Wolfgang Döbereiner]] in 1831 and characterised nine years later by [[John Stenhouse]]. Furan itself was first prepared by [[Heinrich Limpricht]] in 1870, although he called it ''tetraphenol''.<ref>{{cite journal | title = Ueber das Tetraphenol C<sub>4</sub>H<sub>4</sub>O | pages = pp. 90–91 | first = H. | last = Limpricht | volume = 3 | issue = 1 | year = 1870 | journal = Berichte der deutschen chemischen Gesellschaft | doi =10.1002/cber.18700030129}}</ref><ref>{{cite book | first = Ernest Harry | last = Rodd | title = Chemistry of Carbon Compounds: A Modern Comprehensive Treatise | publisher = Elsevier | year = 1971}}</ref>
==Production==
Industrially, furan is manufactured by the palladium-catalyzed decarbonylation of [[furfural]], or by the copper-catalyzed oxidation of [[1,3-butadiene]]:<ref name = ullmann>{{Ullmann | doi = 10.1002/14356007.a12_119.pub2 | title = Furfural and Derivatives | author = H. E. Hoydonckx, W. M. Van Rhijn, W. Van Rhijn, D. E. De Vos, P. A. Jacobs}}</ref>
:[[File:Manufacture of furan.png|450px]]
In the laboratory, furan can be obtained from [[furfural]] by oxidation to furan-2-carboxylic acid, followed by decarboxylation.<ref>{{OrgSynth | author = Wilson, W.C. | title = Furan | collvol = 1 | collvolpages = 274 | year = 1941 | prep = cv1p0274}}</ref> It can also be prepared directly by [[thermal decomposition]] of [[pentose]]-containing materials, cellulosic solids especially pine-wood.
===Synthesis of furans===
The [[Feist–Benary synthesis]] is a classic way to synthesize furans, although many syntheses have been developed.<ref>{{cite journal| author = Hou XL, Cheung HY, Hon TY, Kwan PL, Lo TH, Tong SY, Wong HNC| year = 1998 | volume = 54 | pages = 1955–2020 | title = Regioselective syntheses of substituted furans | doi = 10.1016/S0040-4020(97)10303-9 | journal = [[Tetrahedron (journal)|Tetrahedron]]| issue = 10}}</ref> One of the simplest synthesis methods for furans is the reaction of [[ketone|1,4-diketone]]s with [[phosphorus pentoxide]] (P<sub>2</sub>O<sub>5</sub>) in the [[Paal–Knorr synthesis]]. The [[thiophene]] formation reaction of 1,4-diketones with [[Lawesson's reagent]] also forms furans as side products. Many routes exist for the synthesis of substituted furans.<ref>{{cite journal | doi = 10.3998/ark.5550190.0005.208 | title = Synthesis of 2,4-disubstituted furans and 4,6-diaryl-substituted 2,3-benzo-1,3a,6a-triazapentalenes | year = 2003 | last1 = Katritzky | first1 = Alan R. | journal = Arkivoc | volume = 2004 | issue = 2 | pages = 109}}</ref>
==Chemistry==
Furan is [[aromatic]] because one of the [[lone pair]]s of [[electron]]s on the oxygen atom is [[delocalized electron|delocalized]] into the ring, creating a 4''n''+2 aromatic system (see [[Hückel's rule]]) similar to [[benzene]]. Because of the aromaticity, the molecule is flat and lacks discrete [[double bond]]s. The other lone pair of electrons of the oxygen atom extends in the plane of the flat ring system. The [[Orbital hybridisation|sp<sup>2</sup> hybridization]] is to allow one of the lone pairs of oxygen to reside in a [[p orbital]] and thus allow it to interact within the [[Conjugated system|π system]].
Due to its aromaticity, furan's behavior is quite dissimilar to that of the more typical heterocyclic [[ether]]s such as [[tetrahydrofuran]].
* It is considerably more reactive than [[benzene]] in [[electrophilic substitution]] reactions, due to the electron-donating effects of the oxygen heteroatom. Examination of the resonance contributors shows the increased electron density of the ring, leading to increased rates of electrophilic substitution.<ref>{{cite book |title=Organic Chemistry |edition=Fifth |last=Bruice |first=Paula Y. |year=2007 |publisher=Pearson Prentice Hall |location=Upper Saddle River, NJ |isbn=0-13-196316-3}}</ref>
[[File:Furan Resonance.png|600px|Resonance contributors of furan]]
* Furan serves as a [[diene]] in [[Diels-Alder reaction]]s with electron-deficient [[dienophile]]s such as ethyl (E)-3-nitroacrylate.<ref>{{cite journal | title = The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid | author = Masesane I, Batsanov A, Howard J, Modal R, Steel P | journal = [[Beilstein Journal of Organic Chemistry]] | year = 2006 | volume = 2 | issue = 9 | doi = 10.1186/1860-5397-2-9 | pages = 9 | pmid = 16674802 | pmc = 1524792}}</ref> The reaction product is a mixture of isomers with preference for the [[endo isomer]]:
:[[File:Furan cycloaddition.png|600px|Furan Diels-Alder reaction with ethyl (E)-3-nitroacrylate]]
:Diels-Alder reaction of furan with arynes provides corresponding derivatives of dihydronaphthalenes, which are useful intermediates in synthesis of other polycyclic aromatic compounds.<ref>{{ cite journal | author = M.A. Filatov, S. Baluschev, I.Z. Ilieva, V. Enkelmann, T. Miteva, K. Landfester, S.E. Aleshchenkov, A.V. Cheprakov | title = Tetraaryltetraanthra[2,3]porphyrins: Synthesis, Structure, and Optical Properties | journal = J. Org. Chem. | year = 2012 | volume = 77 | issue = 24 | pages = 11119–11131 | doi = 10.1021/jo302135q }}</ref>
[[File:Reaction of furan with benzyne.tif|center|400 px]]
* [[Hydrogenation]] of furans affords sequentially dihydrofurans and [[tetrahydrofuran]]s.
* In the [[Achmatowicz reaction]], furans converted to dihydropyran compounds.
==Safety==
Furan is found in heat-treated commercial foods and is produced through [[thermal degradation]] of natural food constituents.<ref>{{Cite journal | pmid = 23627283 | year = 2013 | last1 = Anese | first1 = M | last2 = Manzocco | first2 = L | last3 = Calligaris | first3 = S | last4 = Nicoli | first4 = MC | title = Industrially Applicable Strategies for Mitigating Acrylamide, Furan and 5-Hydroxymethylfurfural in Food | doi = 10.1021/jf305085r | journal = Journal of Agricultural and Food Chemistry | pages = 130528102950009 | volume=61 | issue=43}}</ref><ref name=Moro>{{Cite journal | pmid = 22641279 | year = 2012 | last1 = Moro | first1 = S | last2 = Chipman | first2 = JK | last3 = Wegener | first3 = JW | last4 = Hamberger | first4 = C | last5 = Dekant | first5 = W | last6 = Mally | first6 = A | title = Furan in heat-treated foods: Formation, exposure, toxicity, and aspects of risk assessment | volume = 56 | issue = 8 | pages = 1197–211 | doi = 10.1002/mnfr.201200093 | journal = Molecular nutrition & food research}}</ref> Notably, it can be found in roasted coffee, instant coffee, and processed baby foods.<ref name=Moro/><ref>{{cite journal | journal = EFSA Journal | year = 2011 | volume = 9 | issue = 9 | pages = 2347 | author = [[European Food Safety Authority]] | doi = 10.2903/j.efsa.2011.2347}}</ref><ref>{{Cite journal | pmid = 22035212 | year = 2012 | last1 = Waizenegger | first1 = J | last2 = Winkler | first2 = G | last3 = Kuballa | first3 = T | last4 = Ruge | first4 = W | last5 = Kersting | first5 = M | last6 = Alexy | first6 = U | last7 = Lachenmeier | first7 = DW | title = Analysis and risk assessment of furan in coffee products targeted to adolescents | volume = 29 | issue = 1 | pages = 19–28 | doi = 10.1080/19440049.2011.617012 | journal = Food Additives & Contaminants: Part A}}</ref> Research has indicated that coffee made in [[espresso]] [[Espresso machine|makers]], and, above all, coffee made from [[Single-serve coffee container|capsules]], contains more furan than that made in traditional [[Coffeemaker#Electric drip coffeemakers|drip coffee makers]], although the levels are still within safe health limits.<ref>[http://www.sciencedaily.com/releases/2011/04/110413090012.htm "Espresso makers: Coffee in capsules contains more furan than the rest"], ''[[Science Daily]]'', April 14, 2011</ref>
Exposure to furan at doses about 2000 times the projected level of human exposure from foods increases the risk of hepatocellular tumors in rats and mice and bile duct tumors in rats.<ref name=Bakhiya>{{Cite journal | pmid = 20237914 | year = 2010 | last1 = Bakhiya | first1 = N | last2 = Appel | first2 = KE | title = Toxicity and carcinogenicity of furan in human diet | volume = 84 | issue = 7 | pages = 563–78 | doi = 10.1007/s00204-010-0531-y | journal = Archives of toxicology}}</ref> Furan is therefore listed as a possible human carcinogen.<ref name=Bakhiya/>
== See also ==
* [[BS 4994]] – Furan resin as thermoset FRP for chemical process plant equipments
* [[Furanoflavonoid]]
* [[Furanose]]
* [[Furantetracarboxylic acid]]
* [[Simple aromatic ring]]s
== References ==
{{Reflist|30em}}
== External links ==
* [http://www.organic-chemistry.org/synthesis/heterocycles/furans/furans.shtm Recent synthetic methods]
[[Category:Furans| ]]
[[Category:IARC Group 2B carcinogens]]
[[Category:Simple aromatic rings]]
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