Furfural is an organic compound with the formula C4H3OCHO. 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 of sugars, as occurs in a variety of agricultural byproducts, including corncobs, oat, wheatbran, and sawdust. The name furfural comes from the Latin word furfur, meaning bran, referring to its usual source. Furfural is only derived from dried biomass. In addition to ethanol, acetic acid, and sugar, furfural is one of the oldest organic chemicals available readily purified from natural precursors.[6]
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.[7] 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 (C5H4O2).[8]George Fownes named this oil "furfurol" in 1845 (from furfur (bran), and oleum (oil)).[9] In 1848, the French chemist Auguste Cahours determined that furfural was an aldehyde.[10] 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.[11] Additional research by German chemist Heinrich Limpricht supported this idea.[12] From work published in 1877, Baeyer had confirmed his previous belief on the structure of furfural.[13] By 1886, furfurol was being called "furfural" (short for "furfuraldehyde") and the correct chemical structure for furfural was being proposed.[14] By 1887, the German chemist Willy Marckwald had inferred that some derivatives of furfural contained a furan nucleus.[15] In 1901, the German chemist Carl Harries determined furan's structure through work with succindialdehyde and 2-methylfuran, thereby also confirming furfural's proposed structure.[16][17]
Furfural remained relatively obscure until 1922,[6] when the Quaker Oats Company began mass-producing it from oat hulls.[18] Today, furfural is still produced from agricultural byproducts like 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 alkanes.
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 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 (pentoses), particularly xylose.[19]
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.[20]
In the laboratory, furfural can be synthesized from plant material by heating with sulfuric acid[21] or other acids.[22][20] 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.[23] 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.[24] 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,[25][26] cattle feed, activated carbon, mulch/fertiliser, etc.
Uses and occurrence
It is commonly found in many cooked or heated foods such as coffee (55–255mg/kg) and whole grain bread (26mg/kg).[4]
Furfural is an important renewable, non-petroleum based, chemical feedstock. It can be converted into a variety of solvents, polymers, fuels and other useful chemicals by a range of catalyticreduction.[27]
The Pinner reaction refers to the acid catalysed reaction of a nitrile with an alcohol to form an imino ester salt ; this is sometimes referred to as a Pinner salt. The reaction is named after Adolf Pinner, who first described it in 1877. Pinner salts are themselves reactive and undergo additional nucleophilic additions to give various useful products:
Pyrrole is a heterocyclic, aromatic, organic compound, a five-membered ring with the formula C4H4NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, C4H4NCH3. Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme.
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans.
Resorcinol (or resorcin) is a phenolic compound. It is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or meta-isomer). Resorcinol crystallizes from benzene as colorless needles that are readily soluble in water, alcohol, and ether, but insoluble in chloroform and carbon disulfide.
In organic chemistry, the Knoevenagel condensation reaction is a type of chemical reaction named after German chemist Emil Knoevenagel. It is a modification of the aldol condensation.
The Japp–Klingemann reaction is a chemical reaction used to synthesize hydrazones from β-keto-acids and aryl diazonium salts. The reaction is named after the chemists Francis Robert Japp and Felix Klingemann.
The Bischler–Möhlau indole synthesis, also often referred to as the Bischler indole synthesis, is a chemical reaction that forms a 2-aryl-indole from an α-bromo-acetophenone and excess aniline; it is named after August Bischler and Richard Möhlau .
Spermine is a polyamine involved in cellular metabolism that is found in all eukaryotic cells. The precursor for synthesis of spermine is the amino acid ornithine. It is an essential growth factor in some bacteria as well. It is found as a polycation at physiological pH. Spermine is associated with nucleic acids and is thought to stabilize helical structure, particularly in viruses. It functions as an intracellular free radical scavenger to protect DNA from free radical attack. Spermine is the chemical primarily responsible for the characteristic odor of semen.
Viktor Meyer was a German chemist and significant contributor to both organic and inorganic chemistry. He is best known for inventing an apparatus for determining vapour densities, the Viktor Meyer apparatus, and for discovering thiophene, a heterocyclic compound. He is sometimes referred to as Victor Meyer, a name used in some of his publications.
The Reimer–Tiemann reaction is a chemical reaction used for the ortho-formylation of phenols. with the simplest example being the conversion of phenol to salicylaldehyde. The reaction was first reported by Karl Reimer and Ferdinand Tiemann.
Paul Friedländer was a German chemist best known for his research on derivates of indigo and isolation of Tyrian purple from Murex brandaris.
In organic chemistry, the Paal–Knorr synthesis is a reaction used to synthesize substituted furans, pyrroles, or thiophenes from 1,4-diketones. It is a synthetically valuable method for obtaining substituted furans and pyrroles, which are common structural components of many natural products. It was initially reported independently by German chemists Carl Paal and Ludwig Knorr in 1884 as a method for the preparation of furans, and has been adapted for pyrroles and thiophenes. Although the Paal–Knorr synthesis has seen widespread use, the mechanism wasn't fully understood until it was elucidated by V. Amarnath et al. in the 1990s.
Hans Freiherr von Pechmann was a German chemist, renowned for his discovery of diazomethane in 1894. Pechmann condensation and Pechmann pyrazole synthesis. He also first prepared 1,2-diketones, acetonedicarboxylic acid, methylglyoxal and diphenyltriketone; established the symmetrical structure of anthraquinone.
Fischer glycosidation refers to the formation of a glycoside by the reaction of an aldose or ketose with an alcohol in the presence of an acid catalyst. The reaction is named after the German chemist, Emil Fischer, winner of the Nobel Prize in chemistry, 1902, who developed this method between 1893 and 1895.
The Schotten–Baumann reaction is a method to synthesize amides from amines and acid chlorides:
In organic chemistry, the Claisen–Schmidt condensation is the reaction between an aldehyde or ketone having an α-hydrogen with an aromatic carbonyl compound lacking an α-hydrogen. It can be considered as a specific variation of the aldol condensation. This reaction is named after two of its pioneering investigators Rainer Ludwig Claisen and J. Gustav Schmidt, who independently published on this topic in 1880 and 1881. An example is the synthesis of dibenzylideneacetone ( -1,5-diphenylpenta-1,4-dien-3-one).
Carl Theodore Liebermann was a German chemist and student of Adolf von Baeyer.
Oskar Piloty was a German chemist.
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. 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.
Alexander Ellinger was a German chemist and pharmacologist.
1 2 Peters, Fredus N. (1936). "The Furans: Fifteen Years of Progress". Industrial & Engineering Chemistry. 28 (7): 755–759. doi:10.1021/ie50319a002. ISSN0019-7866.
↑ 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 … )
↑ Cahours, Auguste (1848). "Note sur le furfurol"[Note on furfurol]. Annales de Chimie et de Physique. 3rd series (in French). 24: 277–285. (English translation: Cahours, A. (1848). "Observations on furfurol". The Chemical Gazette. 6: 457–460.)
↑ Limpricht, H. (1870). "Ueber das Tetraphenol C4H4O"[On tetraphenol C4H4O]. Berichte der Deutschen Chemischen Gesellschaft (in German). 3: 90–91. doi:10.1002/cber.18700030129. 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.
↑ In 1877, Baeyer published a series of papers on furfural, as he tried to determine its structure.
↑ Tilden, William A., ed. (1886). Watts' Manual of Chemistry: Theoretical and Practical. Vol.II: Chemistry of Carbon-Compounds or, Organic Chemistry (2nded.). Philadelphia, Pennsylvania, USA: P. Blakiston, Son, & Co. pp.379–380.
↑ Brownlee, Harold J.; Miner, Carl S. (1948). "Industrial Development of Furfural". Industrial & Engineering Chemistry. 40 (2): 201–204. doi:10.1021/ie50458a005. ISSN0019-7866.
↑ Cai, Charles M.; Zhang, Taiying; Kumar, Rajeev; Wyman, Charles E. (2014). "Integrated furfural production as a renewable fuel and chemical platform from lignocellulosic biomass". Journal of Chemical Technology & Biotechnology. 89: 2–10. doi:10.1002/jctb.4168.
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