View source for Furfural

{{chembox
|Verifiedfields = changed
|Watchedfields = changed
|verifiedrevid = 477167491
|ImageFileL1 = Furfural.svg
|ImageClassL1 = skin-invert-image
|ImageFileR1 = Furfural-from-xtal-3D-bs-17.png
|ImageClassR1 = bg-transparent
|PIN = Furan-2-carbaldehyde
|OtherNames = Furfural, furan-2-carboxaldehyde, fural, furfuraldehyde, 2-furaldehyde, pyromucic aldehyde
|Section1={{Chembox Identifiers
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 13863629
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = DJ1HGI319P
|InChIKey = HYBBIBNJHNGZAN-UHFFFAOYAD
|ChEBI_Ref = {{ebicite|changed|EBI}} 
|ChEBI = 34768
|ChEMBL_Ref = {{ebicite|correct|EBI}}
|ChEMBL = 189362
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C5H4O2/c6-4-5-2-1-3-7-5/h1-4H
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = HYBBIBNJHNGZAN-UHFFFAOYSA-N
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo = 98-01-1
|PubChem = 7362
|SMILES = c1cc(oc1)C=O
|InChI = 1/C5H4O2/c6-4-5-2-1-3-7-5/h1-4H
|KEGG_Ref = {{keggcite|correct|kegg}}
|KEGG = C14279
}}
|Section2={{Chembox Properties
|C=5 | H=4 | O=2
|Appearance = Colorless oil
|Odor = Almond-like<ref name=PGCH/>
|Density = 1.1601{{nbsp}}g/mL (20{{nbsp}}°C)<ref name=GESTIS>{{GESTIS|ZVG=25010|CAS=98-01-1}}</ref><ref>{{cite journal |last1=Baird |first1=Zachariah Steven |last2=Uusi-Kyyny |first2=Petri |last3=Pokki |first3=Juha-Pekka |last4=Pedegert |first4=Emilie |last5=Alopaeus |first5=Ville|display-authors=3 |title=Vapor Pressures, Densities, and PC-SAFT Parameters for 11 Bio-compounds |journal=International Journal of Thermophysics |date=6 Nov 2019 |volume=40 |issue=11 |page=102 |doi=10.1007/s10765-019-2570-9|bibcode=2019IJT....40..102B |doi-access=free }}</ref>
|MeltingPtC = −37
|MeltingPt_ref = <ref name=GESTIS/>
|BoilingPtC = 162
|BoilingPt_ref = <ref name=GESTIS/>
|Solubility = 83{{nbsp}}g/L<ref name=GESTIS/>
|VaporPressure = 2{{nbsp}}mmHg (20{{nbsp}}°C)<ref name=PGCH/>
|MagSus = −47.1×10<sup>−6</sup>{{nbsp}}cm<sup>3</sup>/mol}}
|Section3={{Chembox Hazards
|FlashPtC = 62
|ExploLimits = 2.1–19.3%<ref name=PGCH/>
|PEL = TWA 5{{nbsp}}ppm (20{{nbsp}}mg/m<sup>3</sup>) [skin]<ref name=PGCH>{{PGCH|0297}}</ref>
|LD50 = 300–500{{nbsp}}mg/kg (oral, mice)<ref name=Ull/>
|REL = No established REL<ref name=PGCH/>
|IDLH = 100{{nbsp}}ppm<ref name=PGCH/>
|LC50 = {{ubl
| 370{{nbsp}}ppm (dog, 6{{nbsp}}hr)
| 175{{nbsp}}ppm (rat, 6{{nbsp}}hr)
| 1037{{nbsp}}ppm (rat, 1{{nbsp}}hr)<ref name=IDLH>{{IDLH|98011|Furfural}}</ref>
}}
|LCLo = {{ubl
| 370{{nbsp}}ppm (mouse, 6{{nbsp}}hr)
| 260{{nbsp}}ppm (rat)<ref name=IDLH/>
}}
}}
|Section4={{Chembox Related
|OtherFunction_label = Furan-2-carbaldehydes
|OtherFunction = {{ubl
| [[Hydroxymethylfurfural]]
| [[Methoxymethylfurfural]]
}}
}}
}}

'''Furfural''' is an [[organic compound]] with the formula C<sub>4</sub>H<sub>3</sub>OCHO. It is a colorless liquid, although commercial samples are often brown. It has an [[aldehyde]] group attached to the 2-position of [[furan]]. It is a product of the [[dehydration reaction|dehydration]] of sugars, as occurs in a variety of [[agriculture|agricultural]] byproducts, including [[maize|corncobs]], [[oat]], [[wheat]] [[bran]], and [[sawdust]]. The name ''furfural'' comes from the [[Latin]] word {{lang|la|furfur}}, meaning [[bran]], referring to its usual source. Furfural is derived only from dried biomass. In addition to [[ethanol]], [[acetic acid]], and [[sugar]], furfural is one of the oldest known organic chemicals available readily purified from natural precursors.<ref name="Peters1936">{{cite journal|last1=Peters|first1=Fredus N.|title=The Furans: Fifteen Years of Progress|journal=Industrial & Engineering Chemistry|volume=28|issue=7|year=1936|pages=755–759|issn=0019-7866|doi=10.1021/ie50319a002}}</ref>

== History ==
Furfural was first isolated in 1821 (published in 1832) by the German chemist [[Johann Wolfgang Döbereiner]], who produced a small sample as a byproduct of [[formic acid]] synthesis.<ref>{{cite journal| title = Ueber die medicinische und chemische Anwendung und die vortheilhafte Darstellung der Ameisensäure |trans-title = On the medical and chemical application and the profitable preparation of formic acid| pages = 141–146| author = J. W. Döbereiner| volume = 3| issue = 2| year = 1832| journal = Annalen der Pharmacie| doi = 10.1002/jlac.18320030206| url = https://zenodo.org/record/1426896 |language=de }} From p. 141: ''"Ich verbinde mit diese Bitte noch die Bemerkung, … Bittermandelöl riechende Materie enthält, … "'' (I join to this request also the observation that the formic acid which is formed by the simultaneous reaction of sulfuric acid and manganese peroxide with sugar and which contains a volatile material that appears oily in an isolated condition and that smells like a mixture of cassia and bitter almond oil … )</ref> In 1840, the Scottish chemist [[John Stenhouse]] found that the same chemical could be produced by distilling a wide variety of crop materials, including corn, oats, bran, and sawdust, with aqueous [[sulfuric acid]]; he also determined furfural's [[empirical formula]] (C<sub>5</sub>H<sub>4</sub>O<sub>2</sub>).<ref>{{cite journal| title = On the Oils Produced by the Action of Sulphuric Acid upon Various Classes of Vegetables. [Abstract]| pages = 939–941| author = John Stenhouse| volume = 5| year = 1843| journal = Abstracts of the Papers Communicated to the Royal Society of London| jstor = 111080| doi=10.1098/rspl.1843.0234| url = https://zenodo.org/record/1432029| doi-access = free}}
* See also: {{cite journal |last1=Stenhouse |first1=John |title=On the oils produced by the action of sulphuric acid upon various classes of vegetables |journal=Philosophical Transactions of the Royal Society of London |date=1850 |volume=140 |pages=467–480 |doi=10.1098/rstl.1850.0024 |s2cid=186214485 |doi-access=free }}</ref> [[George Fownes]] named this oil "furfurol" in 1845 (from ''furfur'' (bran), and ''[[oleum]]'' (oil)).<ref>{{cite journal | title = An Account of the Artificial Formation of a Vegeto-Alkali | pages = 253–262 | author = George Fownes | volume = 135 | year = 1845 | journal = Philosophical Transactions of the Royal Society of London | jstor = 108270 | doi=10.1098/rstl.1845.0008| doi-access = free }}</ref> In 1848, the French chemist [[Auguste André Thomas Cahours|Auguste Cahours]] determined that furfural was an [[aldehyde]].<ref>{{cite journal |last1=Cahours |first1=Auguste |title=Note sur le furfurol |journal=Annales de Chimie et de Physique |date=1848 |volume=24 |pages=277–285 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.$b617955&view=1up&seq=285 |series=3rd series |trans-title=Note on furfurol |language=fr}} (English translation: {{cite journal |last1=Cahours |first1=A. |title=Observations on furfurol |journal=The Chemical Gazette |date=1848 |volume=6 |pages=457–460 |url=https://books.google.com/books?id=lwMAAAAAMAAJ&pg=PA457}})</ref> Determining the structure of furfural required some time: the furfural molecule contains a cyclic [[ether]] ([[furan]]), which tends to break open when it's treated with harsh reagents. In 1870, German chemist [[Adolf von Baeyer]] speculated about the structure of the chemically similar compounds furan and [[2-furoic acid]].<ref>{{cite journal |last1=Baeyer |first1=A. |last2=Emmerling |first2=A. |title=Reduction des Istatins zu Indigblau |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1870 |volume=3 |pages=514–517 |doi=10.1002/cber.187000301169 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3481748&view=1up&seq=520 |trans-title=Reduction of istatin to indigo blue |language=de|url-access=subscription }}</ref> Additional research by German chemist [[Heinrich Limpricht]] supported this idea.<ref>{{cite journal |last1=Limpricht |first1=H. |title=Ueber das Tetraphenol C<sub>4</sub>H<sub>4</sub>O |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1870 |volume=3 |pages=90–91 |doi=10.1002/cber.18700030129 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3481748&view=1up&seq=96 |trans-title=On tetraphenol C<sub>4</sub>H<sub>4</sub>O |language=de}} From p. 90: ''"Die Ansicht, dass die Pyroschleimsäure eine der Salicylsäure ähnliche Constitution besitzt, macht das Auftreten des Tetraphenols bei der Destillation der pyroschleimsauren Salze wahrscheinlich."'' (The belief that 2-furoic acid has a structure similar to salicylic acid makes probable the presence of tetraphenol [furan] during the distillation of salts of 2-furoic acid.) That is, just as heating salts of salicylic acid produces phenol, so heating salts of 2-furoic acid should produce an analog of phenol containing 4 carbon atoms.</ref> From work published in 1877, Baeyer had confirmed his previous belief on the structure of furfural.<ref>In 1877, Baeyer published a series of papers on furfural, as he tried to determine its structure.
* {{cite journal |last1=Baeyer |first1=Adolf |title=Ueber das Furfurol. Erste Mittheilung. |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1877 |volume=10 |pages=355–358 |doi=10.1002/cber.187701001101 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.cl1hz2&view=1up&seq=385 |trans-title=On furfural. First report. |language=de|url-access=subscription }}
* {{cite journal |last1=Baeyer |first1=Adolf |title=Ueber das Furfurol. Zweite Mittheilung. |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1877 |volume=10 |pages=695–698 |doi=10.1002/cber.187701001195 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.cl1hz2&view=1up&seq=729 |trans-title=On furfural. Second report. |language=de|url-access=subscription }}
* {{cite journal |last1=Baeyer |first1=Adolf |title=Ueber das Furfurol. III. Mittheilung. |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1877 |volume=10 |issue=2 |pages=1358–1364 |doi=10.1002/cber.18770100225 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.cl1hz3&view=1up&seq=86 |trans-title=On furfural. Third report. |language=de|url-access=subscription }}</ref> By 1886, furfurol was being called "furfural" (short for "furfuraldehyde") and the correct chemical structure for furfural was being proposed.<ref>{{cite book |editor1-last=Tilden |editor1-first=William A. |title=Watts' Manual of Chemistry: Theoretical and Practical |volume=II: Chemistry of Carbon-Compounds or, Organic Chemistry |date=1886 |publisher=P. Blakiston, Son, & Co. |location=Philadelphia, Pennsylvania, USA |pages=379–380 |edition=2nd |url=https://books.google.com/books?id=uoRNAAAAYAAJ&pg=PA379}}</ref> By 1887, the German chemist [[Willy Marckwald]] had inferred that some derivatives of furfural contained a furan nucleus.<ref>{{cite journal |last1=Marckwald |first1=W. |title=Zur Kenntnis der Furfuranverbindungen |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1887 |volume=20 |issue=2 |pages=2811–2817 |doi=10.1002/cber.188702002140 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.cl1hzr&view=1up&seq=561 |trans-title=(Contribution to our) knowledge of furfural compounds |language=de}}</ref> In 1901, the German chemist [[Carl Harries]] determined furan's structure through work with [[Succinaldehyde|succindialdehyde]] and [[2-methylfuran]], thereby also confirming furfural's proposed structure.<ref>{{cite journal |last1=Harries |first1=C. |title=Ueber den Succindialdehyd |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1901 |volume=34 |issue=2 |pages=1488–1498 |doi=10.1002/cber.19010340225 |url=https://babel.hathitrust.org/cgi/pt?id=iau.31858002459323&view=1up&seq=152 |trans-title=On succindialdehyde |language=de}}</ref><ref>{{cite journal |last1=Harries |first1=C. |title=Ueber die Aufspaltung des Sylvans zum Aldehyd der Lävulinsäure, Pentanonal. Untersuchungen über Bestandtheile des Buchentheers. I. |journal=Berichte der Deutschen Chemischen Gesellschaft |date=1898 |volume=31 |issue=1 |pages=37–47 |doi=10.1002/cber.18980310109 |url=https://babel.hathitrust.org/cgi/pt?id=iau.31858002475550&view=1up&seq=47 |trans-title=On the breakdown of 2-methylfuran into the aldehyde of levulinic acid, pentanonal. Investigations into the components of tar from beech trees. I. |language=de|url-access=subscription }}</ref>

Furfural remained relatively obscure until 1922,<ref name="Peters1936" /> when the [[Quaker Oats Company]] began mass-producing it from oat hulls.<ref name="BrownleeMiner1948">{{cite journal|last1=Brownlee|first1=Harold J.|last2=Miner|first2=Carl S.|title=Industrial Development of Furfural|journal=Industrial & Engineering Chemistry|volume=40|issue=2|year=1948|pages=201–204|issn=0019-7866|doi=10.1021/ie50458a005}}</ref> Today, furfural is still produced from agricultural byproducts like [[bagasse|sugarcane bagasse]] and corn cobs. The main countries producing furfural today are the Dominican Republic, South Africa and China.

==Properties==
Furfural dissolves readily in most polar organic solvents, but it is only slightly soluble in either water or [[alkane]]s.

Furfural participates in the same kinds of reactions as other aldehydes and other aromatic compounds. It exhibits less aromatic character than [[benzene]], as can be seen from the fact that furfural is readily [[hydrogenation|hydrogenated]] to [[tetrahydrofurfuryl alcohol]]. When heated in the presence of acids, furfural irreversibly polymerizes, acting as a [[thermosetting polymer]].

==Production==
Furfural may be obtained by the acid catalyzed dehydration of 5-carbon sugars ([[pentose]]s), particularly [[xylose]].<ref name=JCT>{{cite journal |doi=10.1002/jctb.4168|title=Integrated furfural production as a renewable fuel and chemical platform from lignocellulosic biomass|year=2014|last1=Cai|first1=Charles M.|last2=Zhang|first2=Taiying|last3=Kumar|first3=Rajeev|last4=Wyman|first4=Charles E.|journal=Journal of Chemical Technology & Biotechnology|volume=89|issue=1 |pages=2–10|bibcode=2014JCTB...89....2C }}</ref> 
:[[xylose|{{chem|C|5|H|10|O|5}}]] → {{chem|C|5|H|4|O|2}} + 3 {{chem|H|2|O}}

These sugars may be obtained from [[pentosan]]s obtained from [[hemicellulose]] present in [[lignocellulosic biomass]].

Between 3% and 10% of the mass of crop residue feedstocks can be recovered as furfural, depending on the type of feedstock. Furfural and water evaporate together from the reaction mixture, and separate upon condensation. The global production capacity is about 800,000 tons as of 2012. China is the biggest supplier of furfural, and accounts for the greater part of global capacity. The other two major commercial producers are [[Illovo Sugar]] in South Africa and Central Romana in the Dominican Republic.<ref name="Dalvand2018">{{cite journal|last1=Dalvand|first1=Kaveh |title=Economics of biofuels: Market potential of furfural and its derivatives |journal= Biomass and Bioenergy |volume=115 | year= 2018 |pages=56–63| doi = 10.1016/j.biombioe.2018.04.005|doi-access=free |bibcode=2018BmBe..115...56D }}</ref>

In the laboratory, furfural can be synthesized from plant material by heating with [[sulfuric acid]]<ref>{{OrgSynth | title = Furfural |year = 1921 | volume = 1 | page = 49 | first1 = Roger|last1= Adams|first2=V.|last2=Voorhees | doi=
10.15227/orgsyn.001.0049}}</ref> or other acids.<ref>{{Cite book|title=The chemistry and technology of furfural and its many by-products|last=Zeitsch |first=Karl J. |date=2000|publisher=Elsevier|isbn=978-0-08-052899-1|location=Amsterdam|oclc=162130560|url-access=registration|url=https://archive.org/details/chemistrytechnol00kjze}}</ref><ref name="Dalvand2018" /> With the purpose to avoid toxic effluents, an effort to substitute sulfuric acid with easily separable and reusable solid acid catalysts has been studied around the world.<ref>{{cite journal|last=Gómez Millán |first=Gerardo|author2=El Assal, Zouhair |author3=Nieminen, Kaarlo |author4=Hellsten, Sanna |author5=Llorca, Jordi |author6=Sixta, Herbert |display-authors=3|title=Fast furfural formation from xylose using solid acid catalysts assisted by a microwave reactor|journal=Fuel Processing Technology|date=15 December 2018|volume=182|pages=56–67|doi=10.1016/j.fuproc.2018.10.013 |bibcode=2018FuPrT.182...56G |hdl=2117/125796 |s2cid=106216043 |hdl-access=free }}</ref> The formation and extraction of xylose and subsequently furfural can be favored over the extraction of other sugars with varied conditions, such as acid concentration, temperature, and time.

In industrial production, some lignocellulosic residue remains after the removal of the furfural.<ref>{{cite journal|last=Gómez Millán |first=Gerardo|author2=Bangalore Ashok, R.P.|author3=Oinas, Pekka|author4=Llorca, Jordi|author5=Sixta, Herbert |display-authors=3|title=Furfural production from xylose and birch hydrolysate liquor in a biphasic system and techno-economic analysis |journal=Biomass Conversion and Biorefinery |date=8 April 2020|volume=11 |issue=5 |pages=2095–2106 |doi=10.1007/s13399-020-00702-4|doi-access=free|hdl=2117/330145|hdl-access=free}}</ref> This residue is dried and burned to provide steam for the operation of the furfural plant. Newer and more energy efficient plants have excess residue, which is or can be used for co-generation of electricity,<ref>{{Cite book |title=Life-cycle assessment of biorefineries |editor-last=Edgard |editor-first=Gnansounou |editor2=Pandey, Ashok |isbn=978-0-444-63586-0 |location=Amsterdam, Netherlands |publisher=Elsevier |oclc=967224456 |date=2016-12-20}}</ref><ref>{{Cite book |title=Virtual biorefinery: an optimization strategy for renewable carbon valorization |isbn=978-3-319-26045-7 |location=Cham |publisher=Springer |oclc=932064033 |editor-last1=Bonomi |editor-first1=Antonio |editor-last2=Cavalett |editor-first2=Otavio |editor-last3=Cunha |editor-first3=Marcelo Pereira da |editor-last4=Lima |editor-first4=Marco A. P. |date=2015-12-09}}</ref> cattle feed, activated carbon, mulch/fertiliser, etc.

==Uses and occurrence==
It is commonly found in many cooked or heated foods such as coffee (55–255&nbsp;mg/kg) and whole grain bread (26&nbsp;mg/kg).<ref name=Ull/>

In [[petrochemical industry]], furfural is utilized as a specialized chemical solvent for [[diene]] extraction.<ref>{{Citation |last=Kamm |first=B. |title=Chapter 5 - Catalytic Processes of Lignocellulosic Feedstock Conversion for Production of Furfural, Levulinic Acid, and Formic Acid-Based Fuel Components |date=2013-01-01 |work=New and Future Developments in Catalysis |pages=91–113 |editor-last=Suib |editor-first=Steven L. |url=https://www.sciencedirect.com/science/article/abs/pii/B9780444538789000059 |access-date=2024-10-12 |place=Amsterdam |publisher=Elsevier |isbn=978-0-444-53878-9 |last2=Gerhardt |first2=M. |last3=Dautzenberg |first3=G.}}</ref>

Furfural is an important renewable, non-petroleum based, chemical [[feedstock]] which can be converted into solvents, polymers, fuels and other useful chemicals by a range of [[catalytic]] [[Redox|reduction]].<ref>{{cite journal |last1=Chen |first1=Shuo |last2=Wojcieszak |first2=Robert |last3=Dumeignil |first3=Franck |last4=Marceau |first4=Eric |last5=Royer |first5=Sébastien |display-authors=3|title=How Catalysts and Experimental Conditions Determine the Selective Hydroconversion of Furfural and 5-Hydroxymethylfurfural |journal=Chemical Reviews |volume=118 |issue=22 |pages=11023–11117 |date=26 October 2018 |doi=10.1021/acs.chemrev.8b00134|pmid=30362725 |doi-access=free |hdl=20.500.12210/12953.3 |hdl-access=free }}</ref>

[[Hydrogenation]] of furfural provides [[furfuryl alcohol]] (FA), which is used to produce [[furan resin]]s, which are exploited in [[thermoset polymer matrix]] composites, cements, adhesives, casting resins and coatings.<ref>{{cite book|author=Brydson, J. A.|title=Plastics Materials|url=https://archive.org/details/plasticsmaterial00bryd|url-access=limited|pages=[https://archive.org/details/plasticsmaterial00bryd/page/n838 810]–813|chapter=Furan Resins|editor=J. A. Brydson|year=1999|publisher=Butterworth-Heinemann |location=Oxford|doi=10.1016/B978-075064132-6/50069-3|isbn=978-0-7506-4132-6|edition=Seventh}}</ref> Further hydrogenation of furfuryl alcohol leads to [[tetrahydrofurfuryl alcohol]] (THFA), which is used as a solvent in agricultural formulations and as an [[adjuvant]] to help [[herbicides]] penetrate the leaf structure.

[[Palladium]]-catalyzed [[decarbonylation]] on furfural manufactures industrially [[furan]].<ref name = Ull>{{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|display-authors=3}}</ref>

Another important solvent made from furfural is [[methyltetrahydrofuran]]. Furfural is used to make other [[furan]] derivatives, such as [[furoic acid]], via oxidation,<ref>{{cite journal|title=2-Furoic Acid |author=R. J. Harrison |author2=M. Moyle |journal=Organic Syntheses|volume=36|page=36|year=1956|doi=10.15227/orgsyn.036.0036}}</ref> and furan itself via [[palladium]] catalyzed vapor phase [[decarbonylation]].<ref name=Ull/>

There is a good market for value added chemicals that can be obtained from furfural.<ref name="Dalvand2018" />

== Safety ==

Furfural is [[carcinogenic]] in [[lab animal]]s and [[mutagenic]] in [[single cell organisms]], but there is no data on human subjects. It is classified in [[IARC Group 3]] due to the lack of data on humans and too few tests on animals to satisfy Group 2A/2B criteria. It is [[hepatotoxic]].<ref>{{cite web|title=Furfural (CAS 98-01-1)|url=https://toxnet.nlm.nih.gov/cpdb/chempages/FURFURAL.html |archive-url=https://web.archive.org/web/20181124105906/https://toxnet.nlm.nih.gov/cpdb/chempages/FURFURAL.html|website=Carcinogenic Potency Project |access-date=24 November 2018|archive-date=24 November 2018}}</ref><ref>{{cite journal |title=Dry Cleaning, Some Chlorinated Solvents and Other Industrial Chemicals |journal=IARC Monographs on the Evaluation of Carcinogenic Risks to Humans |date=1995 |volume=63 |pages=393–407 |url=https://monographs.iarc.fr/wp-content/uploads/2018/06/mono63.pdf |access-date=24 November 2018|pmid=9097102 |pmc=7681282 }}</ref><ref>{{cite web |title=Furfural(Group 3)|url=http://www.inchem.org/documents/iarc/vol63/furfural.html |website=IARC |access-date=24 November 2018}}</ref><ref>{{cite report |author=Richard Irwin, Ph.D. |year=1990 |title=NTP TECHNICAL REPORT ON THE TOXICOLOGY AND CARCINOGENESIS STUDIES OF FURFURAL (CAS NO. 98-01-1) IN F344/N RATS AND B6C3F1 MICE (GAVAGE STUDIES) |url=https://ntp.niehs.nih.gov/sites/default/files/ntp/htdocs/lt_rpts/tr382.pdf |publisher=U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES |access-date=24 November 2018}}</ref>

The [[median lethal dose]] is high, 650–900&nbsp;mg/kg (oral, dogs), consistent with its pervasiveness in foods.<ref name=Ull/>

The [[Occupational Safety and Health Administration]] has set a [[permissible exposure limit]] for furfural at 5{{nbsp}}ppm over an eight-hour time-weighted average (TWA), and also designates furfural as a risk for skin absorption.<ref name=PGCH/>

== See also ==
* [[Aniline acetate test]]
* [[Bial's test]]
* [[Molisch's test]]
* [[Tollens' reagent]]

== References ==
{{reflist}}

==External links==
* {{PPDB|368}}

{{Authority control}}

[[Category:Furfurals| ]]
[[Category:Conjugated dienes]]
[[Category:Monomers]]
[[Category:Flavors]]
[[Category:Solvents]]
[[Category:Fuel dyes]]
[[Category:Resins]]
[[Category:2-Furyl compounds]]
[[Category:Substances discovered in the 19th century]]