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Fumaric acid
IUPAC name	(E)-Butenedioic acid
Other names	trans-1,2-Ethylenedicarboxylic acid 2-Butenedioic acid Allomaleic acid Boletic acid Lichenic acid
Identifiers
CAS number	110-17-8
EINECS number	203-743-0
SMILES	OC(=O)C=CC(=O)O
Properties
Molecular formula	C4H4O4
Molar mass	116.07 g/mol
Appearance	White solid
Density	1.635 g/cm³, solid
Melting point	287 °C
Solubility in water	0.63 g/100 mL
Acidity (pKa)	pka1 = 3.03, pka2 = 4.44
Hazards
EU classification	Irritant (Xi)
R-phrases	R36
S-phrases	(S2) S26
Related Compounds
Related carboxylic acids	Maleic acid Succinic acid
Related compounds	Fumaryl chloride Fumaronitrile Dimethyl fumarate Iron(II) fumarate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Fumaric acid is the chemical compound with the formula HO₂CCH=CHCO₂H. This colorless crystalline compound is one of two isomeric unsaturated dicarboxylic acids, the other being maleic acid wherein the carboxylic acid groups are cis. It has a fruit-like taste. The salts and esters of fumaric acid are known as fumarates.

Fumaric acid, when added to food products, is denoted by E number E297.

Contents 1 Biology 2 Medicine 3 Food 4 Chemistry 5 Other uses 6 Safety 7 See also 8 References 9 External links

Fumaric acid is found in fumitory (Fumaria officinalis), bolete mushrooms (specifically Boletus fomentarius var. pseudo-igniarius), lichen, and Iceland moss.

Fumarate is an intermediate in the citric acid cycle used by cells to produce energy in the form of adenosine triphosphate (ATP) from food. It is formed by the oxidation of adenylsuccinate by the enzyme succinate dehydrogenase. Fumarate is then converted by the enzyme fumarase to malate. Human skin naturally produces fumaric acid when exposed to sunlight.^{[citation needed]}

Fumarate is also a byproduct of the urea cycle.

Fumaric acid esters are sometimes used to treat psoriasis, as it has been suggested that the condition is caused by an impairment of fumaric acid production in the skin.^{[citation needed]} A starting dose is 60-105 mg daily, which may be gradually increased to as much as 1,290 mg per day. Side-effects include kidney or gastrointestinal disorders, as well as skin flushing; these are mainly caused by excess intake. Decreased white blood cell counts have been reported with prolonged use.^{[citation needed]}

Fumaric acid is a food acidulent used since 1946 because it is non-toxic. It is generally used in beverages and baking powders for which requirements are placed on purity. It is generally used as a substitute for tartaric acid and occasionally in place of citric acid, at a rate of 1.36 g of citric acid to every 0.91 grams of fumaric acid for the same taste. It is also used in candy to add sourness, similar to the way malic acid is used.

Fumaric acid is inexpensive, so it is typically purchased rather than prepared. It was first prepared from bromosuccinic acid.^[1] A traditional synthesis involves oxidation of furfural (from the processing of maize) using sodium chlorate in the presence of a vanadium-based catalyst.^[2]

The chemical properties of fumaric acid can be anticipated from its component functional groups. This weak acid forms a diester, it undergoes additions across the double bond, and it is an excellent dienophile.

Fumaric acid is used in the manufacture of polyester resins and polyhydric alcohols and as a mordant for dyes.

Fumaric acid converts to the irritant maleic anhydride, upon partial combustion.

• Dermatology
• Photosynthesis
• Maleic acid, the cis-isomer of fumaric acid

1. ^ Volhard, J. "Darstellung von Maleïnsäureanhydrid" Justus Liebig's Annalen der Chemie 1892, volume 268, page 255-6. DOI: 10.1002/jlac.18922680108
2. ^ Milas, N. A. "Fumaric Acid" Organic Synthesis 1943, Collective Volume 2, page 302. Online version

• International Chemical Safety Card 1173

v • d • e Citric Acid Cycle Metabolic Pathway
Oxaloacetate Malate Fumarate Succinate Succinyl-CoA Acetyl-CoA NADH + H+ NAD+ H2O FADH2 FAD CoA + ATP(GTP) Pi + ADP(GDP) + H2O NADH + H+ + CO2 CoA NAD+ H2O H2O NAD(P)+ NAD(P)H + H+ CO2 Citrate cis-Aconitate Isocitrate Oxalosuccinate α-Ketoglutarate

v • d • e Antipsoriatics (D05)
Topical: tars	Tar
Topical: antracens	Dithranol
Topical: psoralens	Trioxysalen - Methoxsalen
Topical: other	Fumaric acid - Calcipotriol - Calcitriol - Tacalcitol - Tazarotene
Systemic: psoralens	Trioxysalen - Methoxsalen - Bergapten
Systemic: retinoids	Etretinate - Acitretin