2-Furoic acid

2-Furoic acid is an organic compound, consisting of a furan ring and a carboxylic acid side-group. Along with other furans, its name is derived from the Latin word furfur, meaning bran, from which these compounds were first produced.^[2] The salts and esters of furoic acids are known as furoates. 2-Furoic acid is most widely encountered in food products as a preservative and a flavouring agent, where it imparts a sweet, earthy flavour.^[3]

2-Furoic Acid

Names
Preferred IUPAC name Furan-2-carboxylic acid[1]
Other names 2-Furoic acid Pyromucic acid 2-Furancarboxylic acid α-Furancarboxylic acid α-Furoic acid 2-Carboxyfuran
Identifiers
CAS Number	88-14-2 Y
3D model (JSmol)	Interactive image
Beilstein Reference	110149
ChEBI	CHEBI:30845 Y
ChemSpider	10251740 Y
ECHA InfoCard	100.001.639
Gmelin Reference	3056
KEGG	C01546
PubChem CID	6919
UNII	P577F6494A Y
CompTox Dashboard (EPA)	DTXSID6041420
InChI InChI=1S/C5H4O3/c6-5(7)4-2-1-3-8-4/h1-3H,(H,6,7) Y Key: SMNDYUVBFMFKNZ-UHFFFAOYSA-N Y InChI=1/C4H9.Li/c1-3-4-2;/h1,3-4H2,2H3;/rC4H9Li/c1-2-3-4-5/h2-4H2,1H3 Key: MZRVEZGGRBJDDB-NESCHKHYAE
SMILES OC(=O)C1=CC=CO1
Properties
Chemical formula	C5H4O3
Molar mass	112.084 g·mol−1
Appearance	White/ Off-White (Beige) Crystalline Powder
Density	0.55 g/cm3
Melting point	128 to 132 °C (262 to 270 °F; 401 to 405 K)
Boiling point	230 to 232 °C (446 to 450 °F; 503 to 505 K)
Solubility in water	Easily soluble in cold and hot water, 27.1 g/L
Acidity (pKa)	3.12 at 25 °C
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Irritating to eyes, respiratory system and skin.
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 1 0
Related compounds
Related compounds	2-Thiophenecarboxylic acid, 3-Furoic acid, Furfuryl alcohol, 2,5-Furandicarboxylic acid, Furfurylamine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

History

The compound was first described by Carl Wilhelm Scheele in 1780, who obtained it by the dry distillation of mucic acid. For this reason it was initially known as pyromucic acid. This was the first known synthesis of a furan compound, the second being furfural in 1821.^[4][5] Despite this, it was furfural which came to set naming conventions for later furans.

Preparation and synthesis

Biotransformation of furfuryl alcohol (R = CH₂OH) or furfural (R = CHO) to 2-furoic acid by Nocardia corallina

2-Furoic acid can be synthesized by the oxidation of either furfuryl alcohol or furfural. This can be achieved either chemically or biocatalytically.

The current industrial route involves the Cannizaro reaction of furfural in an aqueous NaOH solution. This is a disproportionation reaction and produces a 1:1 ratio of 2-furoic acid and furfuryl alcohol (a 50% yield of each).^[6] It remains economical because both products have commercial value. The bio-catalytic route involves the microorganism Nocardia corallina. This produces 2-furoic acid in higher yields: 98% from 2-furfuryl alcohol and 88% from 2-furfural,^[7] but has yet to be commercialised.

Applications and occurrences

Diloxanide, an amebicide derived from 2-feroic acid,^[8] is on the World Health Organization's List of Essential Medicines.^[9]

In terms of commercial uses, 2-furoic acid is often used in the production of furoate esters, some of which are drugs and pesticides.^[10]

In foods

It is a flavoring ingredient and achieved a generally recognized as safe (GRAS) status in 1995 by the Flavor and Extract Manufacturers Association (FEMA). 2-Furoic acid has a distinct odor described as sweet, oily, herbaceous, and earthy.^[3]

2-Furoic acid helps sterilize and pasteurize many foods. It forms in situ from 2-furfural.^[11] 2-Furoic acid is also formed during coffee roasting, with up to 205 mg/kg.^[12]

Optic properties

2-Furoic acid crystals are highly transparent in the 200–2000 nm wavelength region, are stable up to 130 °C, and generally have low absorption in the UV, visible, and IR ranges.^[13] In optical and dielectric studies, 2-furoic acid crystals may act as paraelectrics in the temperature range < 318 K and ferroelectrics in temperature ranges > 318 K.^[14]

Microbial metabolism

2-Furoic acid can be the sole source of carbon and energy for the organism Pseudomonas putida. The organism aerobically degrades the compound. ^{[15] [16]}

Hazards

The LD50 is 100 mg/kg (oral, rats).^[17]

References

1. "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 746. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
2. Senning, Alexander (2006). Elsevier's Dictionary of Chemoetymology. Elsevier. ISBN 0-444-52239-5.
3. Burdock, George (1996). "P–Z indexes". Encyclopedia of Food and Color Additives. Vol. 3. Bob Stern. p. 2359. ISBN 0-8493-9414-7.
4. J. W. Döbereiner (1832). "Ueber die medicinische und chemische Anwendung und die vortheilhafte Darstellung der Ameisensäure" [On the medical and chemical application and the profitable preparation of formic acid]. Annalen der Pharmacie (in German). 3 (2): 141–146. doi:10.1002/jlac.18320030206. 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 … )
5. John Stenhouse (1843). "On the Oils Produced by the Action of Sulphuric Acid upon Various Classes of Vegetables. [Abstract]". Abstracts of the Papers Communicated to the Royal Society of London. 5: 939–941. doi:10.1098/rspl.1843.0234. JSTOR 111080.

   • See also: Stenhouse, John (1850). "On the oils produced by the action of sulphuric acid upon various classes of vegetables". Philosophical Transactions of the Royal Society of London. 140: 467–480. doi:10.1098/rstl.1850.0024. S2CID 186214485.
6. Mariscal, R.; Maireles-Torres, P.; Ojeda, M.; Sádaba, I.; López Granados, M. (2016). "Furfural: a renewable and versatile platform molecule for the synthesis of chemicals and fuels" (PDF). Energy Environ. Sci. 9 (4): 1144–1189. doi:10.1039/C5EE02666K. hdl:10261/184700. ISSN 1754-5692. S2CID 101343477.
7. Pérez, Herminia (2009). "Microbial biocatalytic preparation of 2-furoic acid by oxidation of 2-furfuryl alcohol and 2-furanaldehyde with Nocardia corallina". African Journal of Biotechnology. 8 (10).
8. Farthing, Michael JG (August 2006). "Treatment options for the eradication of intestinal protozoa". Nature Clinical Practice Gastroenterology & Hepatology. 3 (8): 436–445. doi:10.1038/ncpgasthep0557. PMID 16883348. S2CID 19657328.
9. World Health Organization (2019). World Health Organization model list of essential medicines: 21st list 2019. Geneva: World Health Organization. hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
10. Zitt, Myron; Kosoglou, Teddy; Hubbell, James (2007). "Mometasone Furoate Nasal Spray: A Review of Safety and Systemic Effects". Drug Safety. 30 (4): 317–326. doi:10.2165/00002018-200730040-00004. PMID 17408308. S2CID 42398133.
11. Hucker, B.; Varelis, P. (2011). "Thermal decarboxylation of 2-furoic acid and its implication for the formation of furan in foods". Food Chemistry. 126 (3): 1512–1513. doi:10.1016/j.foodchem.2010.12.017.
12. Macheiner, Lukas; Schmidt, Anatol; Karpf, Franz; Mayer, Helmut K. (2021). "A novel UHPLC method for determining the degree of coffee roasting by analysis of furans". Food Chemistry. 341 (Pt 1): 128165. doi:10.1016/j.foodchem.2020.128165. PMID 33038777. S2CID 222280614.
13. Uma, B.; Das, S. Jerome; Krishnan, S.; Boaz, B. Milton (2011). "Growth, optical and thermal studies on organic nonlinear optical crystal: 2-Furoic acid". Physica B: Condensed Matter. 406 (14): 2834–2839. Bibcode:2011PhyB..406.2834U. doi:10.1016/j.physb.2011.04.038.
14. Uma, B.; Murugesan, K. Sakthi; Krishnan, S.; Das, S. Jerome; Boaz, B. Milton (2013). "Optical and dielectric studies on organic nonlinear optical 2-furoic acid single crystals". Optik. 124 (17): 2754–2757. Bibcode:2013Optik.124.2754U. doi:10.1016/j.ijleo.2012.08.075.
15. Limpricht, H. (1870). "Ueber das Tetraphenol C₄H₄O" [On tetraphenol C₄H₄O]. Berichte der Deutschen Chemischen Gesellschaft. 3 (1): 90–91. doi:10.1002/cber.18700030129.
16. KOENIG, KERSTIN (1988). "Molybdenum Involvement in Aerobic Degradation of 2-Furoic Acid by Pseudomonas putida Ful". Applied and Environmental Microbiology. 55 (7): 1829–34. doi:10.1128/aem.55.7.1829-1834.1989. PMC 202958. PMID 16347977.
17. H. E. Hoydonckx; W. M. Van Rhijn; W. Van Rhijn; D. E. De Vos; P. A. Jacobs (2007). "Furfural and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a12_119.pub2. ISBN 978-3527306732.

Further reading

• Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
• "2-Furoic Acid [Material Safety Data Sheet]". Sciencelab.com. October 9, 2005. Archived from the original on October 17, 2012. Retrieved March 15, 2013.