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Furfural
Furfural structure.png
Furfural-3D-vdW.png
IUPAC name
Other names furfural, furan-2-carboxaldehyde, fural, furfuraldehyde, pyromucic aldehyde
Identifiers
CAS number 98-01-1 Yes check.svgY
PubChem 7362
SMILES
InChI
Properties
Molecular formula C5H4O2
Molar mass 96.08 g mol−1
Appearance Colorless oil
Density 1.16 g/mL liquid
Melting point

-36.5 °C

Boiling point

161.7 °C

Solubility in methanol methanol 12.02 M [1]
Hazards
Flash point 62 °C
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Furfural is an industrial chemical compound derived from a variety of agricultural byproducts, including corncobs, oat and wheat bran, and sawdust. The name furfural comes from the Latin word furfur, meaning bran, referring to its usual source.

Furfural is an aromatic aldehyde, with the ring structure shown at right. Its chemical formula is C5H4O2. In its pure state, it is a colorless oily liquid with the odor of almonds, but upon exposure to air it quickly becomes yellow.

Contents

History

Furfural was first isolated in 1832 by the German chemist Johann Wolfgang Döbereiner, who formed a very small quantity of it as a byproduct of formic acid synthesis.[2] At the time, formic acid was formed by the distillation of dead ants, and Döbereiner's ant bodies probably contained some plant matter. 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, and he determined that this chemical had an empirical formula of C5H4O2. In 1901, the German chemist Carl Harries deduced furfural's structure.

Except for occasional use in perfume, furfural remained a relatively obscure chemical until 1922, when the Quaker Oats Company began mass-producing it from oat hulls. Today, furfural is still produced from agricultural byproducts like sugarcane bagasse and corn cobs.

Properties

Furfural's physical properties are summarized in the table at right. Furfural dissolves readily in most polar organic solvents, but is only slightly soluble in either water or alkanes.

Chemically, furfural participates in the same kinds of reactions as other aldehydes and other aromatic compounds. The aromatic stability of furfural is not as great as in benzene, and furfural participates in hydrogenation and other addition reactions more readily than many other aromatics.

When heated above 250 °C, furfural decomposes into furan and carbon monoxide, sometimes explosively.

When heated in the presence of acids, furfural irreversibly solidifies into a hard thermosetting resin.

Production

Many plant materials contain the polysaccharide hemicellulose, a polymer of sugars containing five carbon atoms each. When heated with sulfuric acid, hemicellulose undergoes hydrolysis to yield these sugars, principally xylose. Under the same conditions of heat and acid, xylose and other five carbon sugars undergo dehydration, losing three water molecules to become furfural:

C5H10O5 → C5H4O2 + 3 H2O

For crop residue feedstocks, about 10% of the mass of the original plant matter can be recovered as furfural. Furfural and water evaporate together from the reaction mixture, and separate upon condensation.

The total global production capacity is about 450,000 tons. China is the biggest supplier of furfural, and accounts for around half of global capacity.

In the laboratory, synthesis of furfural from corn cobs takes place by reflux with dilute sulfuric acid [3].

Uses

Furfural is used as a solvent in petrochemical refining to extract dienes (which are used to make synthetic rubber) from other hydrocarbons.

Furfural, as well as its derivative furfuryl alcohol, can be used either by themselves or together with phenol, acetone, or urea to make solid resins. Such resins are used in making fiberglass, some aircraft components, and automotive brakes.

Furfural is also used as a chemical intermediate in the production of the solvents furan and tetrahydrofuran. Hydroxymethylfurfural has been identified in a wide variety of heat processed foods.

A furfural test is conducted in biochemical test. For inference of fats or non - reducing sugar like sucrose.

Experiment Observation Inference
Substance in alcohol + 1ml HCl Conc + few drops of alcoholic alpha naphthol and shake then allow to stand for few minutes red colour appears Fat is present
Substance in water + alcoholic solution of α - naphthol then add few drops of concentrated hydrochloric acid and allow to stand for some time Pale Yellow precipitates obtained non - reducing sugar like sucrose is present

Safety

When ingested or inhaled, furfural can cause intoxication, including euphoria, headache, dizziness, nausea, and eventual unconsciousness and death due to respiratory failure. Contact with furfural irritates the skin and respiratory tract and can cause the lungs to fill with fluid.

Chronic skin exposure can lead to a skin allergy to the substance, as well as an unusual susceptibility to sunburn. In toxicity studies, furfural has led to tumors, mutations, and liver and kidney damage in animals.

References

  1. ^ Solubility of furfuraldehyde in methanol
  2. ^ J. W. Döbereiner (1832). "Ueber die medicinische und chemische Anwendung und die vortheilhafte Darstellung der Ameisensäure". Berichte der deutschen chemischen Gesellschaft 3 (2): 141–146. doi:10.1002/jlac.18320030206.  
  3. ^ Roger Adams and V. Voorhees (1921), "Furfural", Org. Synth. 1: 49, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0280  ; Coll. Vol. 1: 280  
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