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 | |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name Furan-2,5-dione[2] | |||
| Other names | |||
| Identifiers | |||
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3D model (JSmol) | |||
| 106909 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
| ||
| ECHA InfoCard | 100.003.247 | ||
| EC Number |
| ||
| 2728 | |||
| RTECS number |
| ||
| UNII | |||
| UN number | 2215 | ||
| |||
| |||
| Properties | |||
| C4H2O3 | |||
| Molar mass | 98.057 g·mol−1 | ||
| Appearance | White crystals or needles[3] | ||
| Odor | irritating, choking[3] | ||
| Density | 1.48 g/cm3 | ||
| Melting point | 52.8 °C (127.0 °F; 325.9 K) | ||
| Boiling point | 202 °C (396 °F; 475 K) | ||
| Reacts | |||
| Vapor pressure | 0.2 mmHg (20°C)[3] | ||
| −35.8·10−6 cm3/mol | |||
| Hazards | |||
| GHS labelling: | |||
   | |||
| Danger | |||
| H302,H314,H317,H334,H372 | |||
| P260,P264,P270,P272,P280,P285,P301+P312,P301+P330+P331,P302+P352,P303+P361+P353,P304+P340,P304+P341,P305+P351+P338,P310,P314,P321,P330,P333+P313,P342+P311,P363,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 102 °C (216 °F; 375 K) | ||
| Explosive limits | 1.4%-7.1%[3] | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 465 mg/kg (oral, mouse) 850 mg/kg (oral, rat) 875 mg/kg (oral, rabbit) 390 mg/kg (oral, guinea pig) 400 mg/kg (oral, rat)[4] | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | TWA 1 mg/m3 (0.25 ppm)[3] | ||
REL (Recommended) | TWA 1 mg/m3 (0.25 ppm)[3] | ||
IDLH (Immediate danger) | 10 mg/m3[3] | ||
| Safety data sheet (SDS) | MSDS at J. T. Baker | ||
| Related compounds | |||
Relatedacid anhydrides | Succinic anhydride | ||
Related compounds | Maleic acid | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Maleic anhydride is anorganic compound with the formulaC2H2(CO)2O. It is theacid anhydride ofmaleic acid. It is a colorless or white solid with an acrid odor. It is produced industrially on a large scale for applications incoatings andpolymers.[5]
Maleic anhydride is a planar molecule. By virtue of the acid anhydride group, the alkene is electrophilic.
On account of its cycle of 4 π electrons in an array of 5 atoms with p orbitals, maleic anhydride was long thought to exhibitantiaromaticity. However, a thermochemical study concluded that only 8 kJ/mol of destabilization energy can be ascribed to this effect, making it weakly antiaromatic at best.[6]
Maleic anhydride is produced by vapor-phase oxidation ofn-butane.[7][8] The overall process converts the methyl groups to carboxylate anddehydrogenates the backbone. The selectivity of the process reflects the robustness of maleic anhydride, with its conjugated double-bond system. Traditionally maleic anhydride was produced by theoxidation ofbenzene or otheraromatic compounds. As of 2006, only a few smaller plants continue to use benzene.
In both cases, benzene and butane are fed into a stream of hot air, and the mixture is passed through a catalyst bed at high temperature. The ratio of air to hydrocarbon is controlled to prevent the mixture from igniting.Vanadium pentoxide andmolybdenum trioxide are the catalysts used for the benzene route, whereasvanadium phosphate is used for the butane route:[5]
The main competing process entails full combustion of the butane, a conversion that is twice as exothermic as the partial oxidation.
The traditional method using benzene became uneconomical due to the high and still rising benzene prices and by complying with theregulations of benzeneemissions. In addition, in the production of maleic anhydride (4 C-atoms) a third of the original carbon atoms is lost as carbon dioxide when using benzene (6 carbon atoms). The modern catalytic processes start from a 4-carbon molecule and only attachesoxygen and removes water; the 4-C-base body of the molecule remains intact. Overall, the newer method is therefore morematerial efficient.[9]
Parallels exist with the production ofphthalic anhydride: While older methods usenaphthalene, modern methods useo-xylene as feedstock.
The chemistry of maleic anhydride is very rich, reflecting its ready availability and bifunctional reactivity. Maleic anhydride hydrolyzes, producingmaleic acid,cis−HOOC−CH=CH−COOH. With alcohols, the half-ester is generated, e.g.,cis−HOOC−CH=CH−COOCH3. With amines, maleic anhydride givesmaleamic acids.[10]
Maleic anhydride is a classic substrate forDiels-Alder reactions.[11] It was used for work in 1928, on the reaction between maleic anhydride and 1,3-butadiene, for whichOtto Paul Hermann Diels andKurt Alder were awarded theNobel Prize in 1950.[12] It is through this reaction that maleic anhydride is converted to many pesticides and pharmaceuticals. Their 1928 patent also provided many other examples of reactions involving maleic anhydride, such as the reaction withcyclopentadiene to formnadic anhydride.[13]
At higher temperatures, the half salts, half esters of maleic acid undergo theMichael reaction with active methylene or methine compounds such as malonate or acetoacetate esters in the presence of sodium acetate catalyst. These intermediates were used for the same Krebs cycle intermediates aconitic and isocitric acids.[14][15]
Maleic anhydridedimerizes in aphotochemical reaction to form cyclobutane tetracarboxylic dianhydride (CBTA). This compound is used in the production ofpolyimides and as an alignment film forliquid crystal displays.[16]
It is also a ligand formingmetal-alkene complexes, examples beingPt(PPh3)2(MA) andFe(CO)4(MA).[17]
Around 50% of world maleic anhydride output is used in the manufacture ofunsaturated polyester resins (UPR).[citation needed] These resins are used in diverse applications such asvehicles,construction,furniture, andmachinery.[18]Chopped glass fibers are added to UPR to produce fiberglass reinforced plastics.
Maleic anhydride is hydrogenated to1,4-butanediol (BDO), used in the production ofthermoplastic polyurethanes, elastane/Spandex fibers,polybutylene terephthalate (PBT) resins and many other products.[citation needed]
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Diels-Alder reaction of maleic anhydride andbutadiene andisoprene gives the respectivetetrahydrophthalic anhydrides which can be hydrogenated to the corresponding hexahydrophthalic anhydrides. These species are used as curing agents inepoxy resins.[19] Another market for maleic anhydride is lubricating oil additives, which are used in gasoline and diesel enginecrankcase oils as dispersants and corrosion inhibitors. Changes in lubricant specifications and more efficient engines have had a negative effect on the demand for lubricating oil additives, giving flat growth prospects for maleic anhydride in this application.
A number of smaller applications exist for maleic anhydride. Personal care products consuming maleic anhydride include hair sprays, adhesives and floor polishes. Maleic anhydride is also a precursor to compounds used for water treatment detergents, insecticides and fungicides, pharmaceuticals, and other copolymers.
The maleic anhydride group occurs in several natural products, some of which show promising therapeutic or pesticidal activity.[20] In thewood science, maleic anhydride in combination with other agents, has been used for protection and modification of wood in order to improve its material properties.[21][22]
| Region | 2015 |
|---|---|
| North America | 370 kt (410,000 short tons) |
| South & Central America | 46 kt (51,000 short tons) |
| Western Europe | 307 kt (338,000 short tons) |
| Central & Eastern Europe | 60 kt (66,000 short tons) |
| Asia | 1,864 kt (2,055,000 short tons) |
| Africa | 14 kt (15,000 short tons) |
| Total | 2,771 kt (3,055,000 short tons) |
Source: Kirk & Othmer[full citation needed]
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Liquid maleic anhydride is available in road tankers and/or tank-containers which are made of stainless steel, which are insulated and provided with heating systems to maintain the temperature of 65–75 °C (149–167 °F). Tank cars must be approved for the transport of molten maleic anhydride.
Liquid/molten maleic anhydride is a dangerous material in accordance with RID/ADR.
Solid maleic anhydride pellets are transported by trucks. Packaging is generally in 25 kg (55 lb) polyethylene bags.
This compound poses relatively low-risk environmental hazards, an important feature for some applications. In humans, exposure to maleic anhydride may cause irritation to the respiratory tract, eyes, exposedmucosa, and skin. Maleic anhydride is also a skin and respiratory sensitizer.[23]
Maleic anhydride is a low hazard profile chemical. Maleic anhydride rapidlyhydrolyzes to form maleic acid in the presence of water and hence environmental exposures to maleic anhydride itself are unlikely. Maleic acid isbiodegradable under aerobic conditions in sewage sludge as well as in soil and water.
Food starch for use in night markets sold from a supplier inTainan city,Taiwan, were found to contain maleic anhydride in December 2013. The supplier was investigated regarding the 300 t (330 short tons) of tainted starch; an earlier inspection in November had found 32 t (35 short tons).[24]
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