Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Furan: Difference between pages

{{Short description|Heterocyclic organic compound,}}

{{About|the industrial chemical compound}}

{{Chembox|Watchedfields=changed

| verifiedrevid=477167468

| ImageFileL1=Furan-2D-full.svg

| ImageNameL1=Full structural formula of furan

| ImageFileR1_Ref={{chemboximage|correct|??}}

| ImageFileR1=Furan-2D-numbered.svg

| ImageNameR1=Skeletal formula showing numbering convention

| ImageFileL2=Furan-CRC-MW-3D-balls-A.png|ImageNameL2=Ball-and-stick model

| ImageFileR2=Furan-CRC-MW-3D-vdW.png|ImageNameR2=Space-filling model

| PIN=Furan<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 392 | doi = 10.1039/9781849733069-FP001 | isbn = 978-0-85404-182-4}}</ref>

| SystematicName=1,4-Epoxybuta-1,3-diene<br />1-Oxacyclopenta-2,4-diene

| OtherNames=Oxole<br />Oxa[5]annulene<br/>1,4-Epoxy-1,3-butadiene<br />5-Oxacyclopenta-1,3-diene<br />5-Oxacyclo-1,3-pentadiene<br />Furfuran<br />Divinylene oxide

| Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 110-00-9

| Beilstein = 103221

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| ChEMBL = 278980

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 7738

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 35559

| EC_number = 203-727-3

| Gmelin = 25716

| KEGG_Ref = {{keggcite|correct|kegg}}

| PubChem = 8029

| RTECS = LT8524000

| UNNumber = 2389

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = UC0XV6A8N9

| SMILES = c1ccoc1

|Section2={{Chembox Properties

| C=4 | H=4 | O=1

| Appearance = Colorless, volatile liquid

| Density = 0.936 g/mL

| MeltingPtC = −85.6

| BoilingPtC = 31.3

| Solubility =

| MagSus = -43.09·10⁻⁶ cm³/mol

|Section3={{Chembox Hazards

| MainHazards =

| FlashPtC = −36

| AutoignitionPtC = 390

| ExploLimits = Lower: 2.3%<br>Upper: 14.3% at 20&nbsp;°C

| NFPA-H = 3

| NFPA-F = 4

| NFPA-R = 1

| GHSPictograms = {{GHS02}}{{GHS07}}{{GHS08}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|224|302|315|332|341|350|373|412}}

| PPhrases = {{P-phrases|201|202|210|233|240|241|242|243|260|261|264|270|271|273|280|281|301+312|302+352|303+361+353|304+312|304+340|308+313|312|314|321|330|332+313|362|370+378|403+235|405|501}}

| LD50 = > 2 g/kg (rat)

| ExternalSDS = [https://web.archive.org/web/20171124235603/http://www.pennakem.com/msds/110-00-9_Furan_PAK_msds.pdf Pennakem]

|Section4={{Chembox Related

| OtherFunction = [[Pyrrole]]<br />[[Thiophene]]

| OtherFunction_label = [[heterocycle]]s

| OtherCompounds = [[Tetrahydrofuran]] (THF)<br />[[2,5-Dimethylfuran]]<br />[[Benzofuran]]<br />[[Dibenzofuran]]

}}|Section5={{Chembox Structure

| CrystalStruct =

| PointGroup = C_2v

'''Furan''' is a [[Heterocyclic compound|heterocyclic]] [[organic compound]], consisting of a five-membered [[aromatic]] [[Ring (chemistry)|ring]] with four [[carbon]] [[Atom|atoms]] and one [[oxygen]] atom. Chemical compounds containing such rings are also referred to as furans.

Furan is a colorless, [[flammable]], highly [[Volatility (chemistry)|volatile]] liquid with a [[boiling point]] close to room temperature. It is soluble in common organic [[Solvent|solvents]], including [[ethanol|alcohol]], [[diethyl ether|ether]], and [[acetone]], and is slightly soluble in [[water]].<ref>{{cite book | first1 = Hans Dieter | last1 = Jakubke | first2 = Hans | last2 = Jeschkeit | title = Concise Encyclopedia of Chemistry | publisher = Walter de Gruyter | isbn = 0-89925-457-8 | pages = [https://archive.org/details/conciseencyclope00eagl/page/1 1–1201] | year = 1994 | url-access = registration | url = https://archive.org/details/conciseencyclope00eagl/page/1 }}</ref> Its odor is "strong, ethereal; [[chloroform]]-like".<ref>[https://www.cdc.gov/niosh/docs/2016-171/pdfs/2016-171.pdf#page=16&zoom=auto,-76,688 DHHS (NIOSH) Publication No. 2016–171], p. 2, Accessed Nov 2019</ref> It is [[toxic]] and may be [[carcinogenic]] in humans. Furan is used as a starting point for other [[speciality chemicals]].<ref name="ullmann" />

== History ==

The name "furan" comes from the [[Latin]] ''furfur'', which means [[bran]]<ref>{{cite book | first = Alexander | last = Senning | title = Elsevier's Dictionary of Chemoetymology | publisher = Elsevier | date = 2006 | isbn = 0-444-52239-5}}</ref> ([[furfural]] is produced from bran). 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" (as if it were a four-carbon analog to [[phenol]], C₆H₅OH).<ref>{{cite journal | title = Ueber das Tetraphenol C₄H₄O | pages = 90–91 | first = H. | last = Limpricht | author-link = Heinrich Limpricht | volume = 3 | issue = 1 | year = 1870 | journal = Berichte der Deutschen Chemischen Gesellschaft | doi =10.1002/cber.18700030129| url = https://zenodo.org/record/1424994 }}</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 | first1 = H. E. | last1 = Hoydonckx | first2 = W. M. | last2 = Van Rhijn | first3 = W. | last3 = Van Rhijn | first4 = D. E. | last4 = De Vos | first5 = P. A. | last5 = Jacobs}}</ref>

:[[File:Manufacture of furan.png|450px]]

In the laboratory, furan can be obtained from [[furfural]] by oxidation to 2-furoic acid, followed by [[decarboxylation]].<ref>{{OrgSynth | last = Wilson | first = 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, and [[cellulose|cellulosic]] solids, especially [[pine]] wood.

===Synthesis of furans===

The [[Feist–Benary synthesis]] is a classic way to synthesize furans. The reaction involves alkylation of 1,3-[[diketone]]s with α-bromoketones followed by dehydration of an intermediate hydroxy[[dihydrofuran]].<ref>{{cite journal|last1=Hou |first1=X. L. |last2=Cheung |first2=H. Y. |last3=Hon |first3=T. Y. |last4=Kwan |first4=P. L. |last5=Lo |first5=T. H. |last6=Tong |first6=S. Y. |last7=Wong |first7=H. N. | 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> The other traditional route involve the reaction of [[ketone|1,4-diketone]]s with [[phosphorus pentoxide]] (P₂O₅) in the [[Paal–Knorr synthesis]].<ref name=Gil>{{cite book |last1=Gilchrist |first1=Thomas L. |title=Heterocyclic Chemistry |date=1997 |publisher=Longman |location=Liverpool |page=209-212 |edition=3rd}}</ref>

Many routes exist for the synthesis of substituted furans.<ref>{{cite journal | doi = 10.15227/orgsyn.084.0199 | title = Electrophilic Cyclization with N-Iodosuccinimide: Preparation of 5-(4-Bromophenyl)-3-Iodo-2-(4-Methyl-Phenyl)Furan | journal = Organic Syntheses | date = 2007 | volume = 84 | page = 199|author=Adam Sniady, Marco S. Morreale, Roman Dembinski}}</ref><ref>{{cite journal |doi=10.15227/orgsyn.076.0263 |title=Isomerization of b-Alkynyl Allylic Alcohols to Furans Catalyzed by Silver Nitrate on Silica Gel: 2-Pentyl-3-Methyl-5-Heptylfuran |journal=Organic Syntheses |date=1999 |volume=76 |page=263|author=James A. Marshall, Clark A. Sehon}}</ref>

<gallery caption="Furan in nature and commerce" widths="180px" heights="120px">

File:Ranitidine Structural Formulae.png|The drug Zantac, also known as [[ranitidine]].

File:Rosefuran-2D-skeletal.png|[[Rosefuran]], an aroma compound found in rose oil.<ref name=Gil/>

File:Furfural.svg|[[Furfural]], derived from sugars, is the major source of furans

File:MethanofuranFeb2011.png|[[methanofuran]] is a cofactor in [[methanogenesis]].

</gallery>

==Structure and bonding==

Furan has [[aromatic]] character 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''&nbsp;+&nbsp;2 aromatic system (see [[Hückel's rule]]). The aromaticity is modest relative to that for [[benzene]] and related heterocycles [[thiophene]] and [[pyrrole]]. The [[resonance energy|resonance energies]] of benzene, [[pyrrole]], [[thiophene]], and furan are, respectively, 152, 88, 121, and 67 kJ/mol (36, 21, 29, and 16 kcal/mol). Thus, these heterocycles, especially furan, are far less aromatic than benzene, as is manifested in the lability of these rings.<ref>{{March6th|page=62}}</ref> The molecule is flat but the C=C groups attached to oxygen retain significant [[double bond]] character. The other lone pair of electrons of the oxygen atom extends in the plane of the flat ring system.

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=5th |last=Bruice |first=Paula Y. |year=2007 |publisher=Pearson Prentice Hall |location=Upper Saddle River, NJ |isbn=978-0-13-196316-0}}</ref>

::[[File:Furan resonance with arrows.svg|600px|Resonance contributors of furan]]

==Reactivity==

Because of its partial aromatic character, furan's behavior is intermediate between that of an enol ether and an aromatic ring. It is dissimilar vs [[diethyl ether|ether]]s such as [[tetrahydrofuran]].

Like enol ethers, 2,5-disubstituted furans are susceptible to hydrolysis to reversibly give 1,4-diketones.

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 |last1=Masesane |first1=I. |last2=Batsanov |first2=A. |last3=Howard |first3=J. |last4=Modal |first4=R. |last5=Steel |first5=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 |doi-access=free }}</ref> The reaction product is a mixture of isomers with preference for the [[endo isomer|''endo'' isomer]]:

::[[File:Furan cycloaddition.svg|600px|Furan Diels–Alder reaction with ethyl (''E'')-3-nitroacrylate]]

Diels-Alder reaction of furan with arynes provides corresponding derivatives of [[dihydronaphthalene]]s, which are useful intermediates in synthesis of other [[polycyclic aromatic hydrocarbon|polycyclic aromatic compounds]].<ref>{{cite journal|last1=Filatov|first1=M. A.|last2=Baluschev|first2=S.|last3=Ilieva|first3=I. Z.|last4=Enkelmann|first4=V.|last5=Miteva|first5=T.|last6=Landfester|first6=K.|author-link6=Katharina Landfester|last7=Aleshchenkov|first7=S. E.|last8=Cheprakov|first8=A. V.|year=2012|title=Tetraaryltetraanthra[2,3]porphyrins: Synthesis, Structure, and Optical Properties|url=https://s3.amazonaws.com/academia.edu.documents/51537332/Tetraaryltetraanthra23porphyrins_synthes20170128-30836-19uulyz.pdf?response-content-disposition=inline%3B+filename%3DTetraaryltetraanthra_2_3_porphyrins_Synt.pdf&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWOWYYGZ2Y53UL3A%2F20200219%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20200219T215659Z&X-Amz-Expires=3600&X-Amz-SignedHeaders=host&X-Amz-Signature=c00193208ea0765b1027679f11da29ad6222abb3f1a4ef8bcdc900375ea22418|url-status=dead|journal=J. Org. Chem.|volume=77|issue=24|pages=11119–11131|doi=10.1021/jo302135q|pmid=23205621|archive-url=https://web.archive.org/web/20200219215759/https://s3.amazonaws.com/academia.edu.documents/51537332/Tetraaryltetraanthra23porphyrins_synthes20170128-30836-19uulyz.pdf?response-content-disposition=inline%3B+filename%3DTetraaryltetraanthra_2_3_porphyrins_Synt.pdf&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWOWYYGZ2Y53UL3A%2F20200219%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20200219T215659Z&X-Amz-Expires=3600&X-Amz-SignedHeaders=host&X-Amz-Signature=c00193208ea0765b1027679f11da29ad6222abb3f1a4ef8bcdc900375ea22418|archive-date=2020-02-19}}</ref>

::[[File:Reaction_of_furan_with_benzyne.svg|400px|Reaction of furan with a benzyne]]

* It is considerably more reactive than [[benzene]] in [[electrophilic substitution]] reactions, due to the electron-donating effects of the oxygen heteroatom. It reacts with bromine at 0 °C to give 2-bromofuran.

* [[Hydrogenation]] of furans sequentially affords [[dihydrofuran]]s and [[tetrahydrofuran]]s.{{cn|date=September 2023}}

* In the [[Achmatowicz reaction]], furans are converted to [[dihydropyran]] compounds.

* [[Pyrrole]] can be prepared industrially by treating furan with [[ammonia]] in the presence of solid acid [[catalyst]]s, such as [[silica|SiO₂]] and [[alumina|Al₂O₃]].<ref name="Ullmann">{{Ullmann|first=Albrecht Ludwig |last=Harreus |title=Pyrrole |doi=10.1002/14356007.a22_453}}</ref>

==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 = M. C. | url = http://www.chtf.stuba.sk/~szolcsanyi/education/files/Organicka%20chemia%20II/Prednaska%207_Derivaty%20karboxylovych%20kyselin_Vlastnosti,%20priprava%20a%20reakcie/Doplnkove%20studijne%20materialy/Acid%20halides/Industrially%20Applicable%20Strategies%20for%20Mitigating%20Acrylamide.pdf | archive-url = https://web.archive.org/web/20170808072346/http://www.chtf.stuba.sk/~szolcsanyi/education/files/Organicka%20chemia%20II/Prednaska%207_Derivaty%20karboxylovych%20kyselin_Vlastnosti,%20priprava%20a%20reakcie/Doplnkove%20studijne%20materialy/Acid%20halides/Industrially%20Applicable%20Strategies%20for%20Mitigating%20Acrylamide.pdf | url-status = dead | archive-date = 2017-08-08 | 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 = 10209–14 | volume=61 | issue=43}}</ref><ref name=Moro>{{Cite journal | pmid = 22641279 | year = 2012 | last1 = Moro | first1 = S. | last2 = Chipman | first2 = J. K. | last3 = Wegener | first3 = J. W. | 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 = 1197–1211 | doi = 10.1002/mnfr.201200093 | journal = Molecular Nutrition & Food Research| hdl = 1871/41889 | s2cid = 12446132 | url = https://research.vu.nl/ws/files/674101/296515.pdf }}</ref> It can be found in roasted [[coffee]], instant coffee, and processed [[baby food]]s.<ref name=Moro/><ref>{{cite journal | title = Update on furan levels in food from monitoring years 2004–2010 and exposure assessment | journal = EFSA Journal | year = 2011 | volume = 9 | issue = 9 | pages = 2347 | author = European Food Safety Authority | doi = 10.2903/j.efsa.2011.2347| author-link = European Food Safety Authority | doi-access = free }} {{open access}} </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 = D. W. | 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| s2cid = 29027966 }}</ref> Research has indicated that coffee made in [[espresso]] [[Espresso machine|makers]] and coffee made from [[Single-serve coffee container|capsules]] contain more furan than that made in traditional [[Coffeemaker#Electric drip coffeemakers|drip coffee makers]], although the levels are still within safe health limits.<ref>{{cite news|url=https://www.sciencedaily.com/releases/2011/04/110413090012.htm |title=Espresso makers: Coffee in capsules contains more furan than the rest |website=[[Science Daily]] |date=April 14, 2011}}</ref>

Exposure to furan at doses about 2,000 times the projected level of human exposure from foods increases the risk of [[liver cancer|hepatocellular tumors]] in rats and mice and [[Cholangiocarcinoma|bile duct tumors]] in rats.<ref name=Bakhiya>{{Cite journal | pmid = 20237914 | year = 2010 | last1 = Bakhiya | first1 = N. | last2 = Appel | first2 = K. E. |url= https://media.ellinikahoaxes.gr/uploads/2016/12/10.1007@s00204-010-0531-y.pdf | title = Toxicity and carcinogenicity of furan in human diet | volume = 84 | issue = 7 | pages = 563–578 | doi = 10.1007/s00204-010-0531-y | journal = Archives of Toxicology| s2cid = 19389984 }}</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

* [[Furanocoumarin]]

* [[Furanoflavonoid]]

* [[Furanose]]

* [[Furantetracarboxylic acid]]

* [[Simple aromatic ring]]s

* [[Furan fatty acids]]

* [[Tetrahydrofuran]]

== References ==

{{Reflist|30em}}

== External links ==

{{commons category|Furan}}

* [https://www.organic-chemistry.org/synthesis/heterocycles/furans/furans.shtm Recent synthetic methods]

{{Simple aromatic rings}}

{{Authority control}}

[[Category:Furans| ]]

[[Category:IARC Group 2B carcinogens]]

[[Category:Simple aromatic rings]]

[[Category:Substances discovered in the 19th century]]