Adipic acid

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Adipic acid
Adipic acid
Names
IUPAC name
hexanedioic acid
Other names
hexane-1,6-dioic acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.250 Edit this at Wikidata
E number E355 (antioxidants, ...)
KEGG
UNII
  • InChI=1S/C6H10O4/c7-5(8)3-1-2-4-6(9)10/h1-4H2,(H,7,8)(H,9,10) checkY
    Key: WNLRTRBMVRJNCN-UHFFFAOYSA-N checkY
  • InChI=1/C6H10O4/c7-5(8)3-1-2-4-6(9)10/h1-4H2,(H,7,8)(H,9,10)
    Key: WNLRTRBMVRJNCN-UHFFFAOYAY
  • O=C(O)CCCCC(=O)O
  • C(CCC(=O)O)CC(=O)O
Properties
C6H10O4
Molar mass 146.142 g·mol−1
Appearance White crystals (monoclinic)[1]
Density 1.36 g/cm3
Melting point 152.1 °C (305.8 °F; 425.2 K)
Boiling point 337.5 °C (639.5 °F; 610.6 K)
fairly soluble[2]
Acidity (pKa) 4.43, 5.41
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Flash point 196 °C
Lethal dose or concentration (LD, LC):
3600 mg/kg (rat)
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Adipic acid is the organic compound with the formula (CH2)4(COOH)2. From the industrial perspective, it is the most important dicarboxylic acid: About 2.5 billion kilograms of this white crystalline powder are produced annually, mainly as a precursor for the production of nylon. Adipic acid otherwise rarely occurs in nature.[3]

Preparation

Historically, adipic acid was prepared from various fats using oxidation. Currently adipic acid is produced from a mixture of cyclohexanol and cyclohexanone called "KA oil", the abbreviation of "ketone-alcohol oil." The KA oil is oxidized with nitric acid to give adipic acid, via a multistep pathway. Early in the reaction the cyclohexanol is converted to the ketone, releasing nitrous acid:

HOC6H11 + HNO3 → OC6H10 + HNO2 + H2O

Among its many reactions, the cyclohexanone is nitrosated, setting the stage for the scission of the C-C bond:

HNO2 + HNO3 → NO+NO3- + H2O
OC6H10 + NO+ → OC6H9-2-NO + H+

Side products of the method include glutaric and succinic acids.[3]

Related processes start from cyclohexanol, which is obtained from the hydrogenation of phenol.[3]

Alternative methods of production

Several methods have been developed by carbonylation of butadiene. For example, the hydrocarboxylation proceeds as follows:[3]

CH2=CHCH=CH2 + 2 CO + 2 H2O → HO2C(CH2)4CO2H

A method has been reported that utilizes principles of green chemistry in that water is the only by-product. Cyclohexene is oxidized with hydrogen peroxide using a tungstate-based catalyst and a phase transfer catalyst.[4] The waste product is water.

Uses

By far the majority of the 2.5 billion kg of adipic acid produced annually is used as monomer for the production of nylon by a polycondensation reaction with hexamethylene diamine forming 6,6-nylon. Other major applications also involve polymers: it is a monomer for production of Polyurethane and its esters are plasticizers, especially in PVC.

In medicine

Adipic acid has been incorporated into controlled-release formulation matrix tablets to obtain pH-independent release for both weakly basic and weakly acidic drugs. It has also been incorporated into the polymeric coating of hydrophilic monolithic systems to modulate the intragel pH, resulting in zero-order release of a hydrophilic drug. The disintegration at intestinal pH of the enteric polymer shellac has been reported to improve when adipic acid was used as a pore-forming agent without affecting release in the acidic media. Other controlled-release formulations have included adipic acid with the intention of obtaining a late-burst release profile.[5]

In foods

Small but significant amounts of adipic acid are used as a food ingredient as a flavorant and gelling aid.[6] It is used in some calcium carbonate antacids to make them tart.

Safety

Adipic acid, like most carboxylic acids, is a mild skin irritant. It is mildly toxic, with an LD50 of 3600 mg/kg for oral ingestion by rats.[3]

References

  1. ^ http://onlinelibrary.wiley.com/doi/10.1002/recl.19410600805/abstract
  2. ^ Gaivoronskii, A. N.; Granzhan, V. A. (2005), "Solubility of Adipic Acid in Organic Solvents and Water", Russian Journal of Applied Chemistry, 78 (3): 404–08, doi:10.1007/s11167-005-0305-0
  3. ^ a b c d e Musser, M. T. (2005), "Adipic Acid", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a01+269.
  4. ^ Sato, K.; Aoki, M.; Noyori, R. (1998), "A "Green" route to adipic acid: direct oxidation of cyclohexenes with 30 percent hydrogen peroxide", Science, 281 (5383): 1646–47, doi:10.1126/science.281.5383.1646.
  5. ^ Roew, Raymond (2009), "Adipic Acid", Handbook of Pharmaceutical Excipients, pp. 11–12
  6. ^ "Cherry Jell-O Nutrition Facts". Kraft Foods. Retrieved 21 Mar 2012.

Appendix

  • E-number E355.
  • U.S. FDA citations - GRAS (21 CFR 184.1009), Indirect additive (21 CFR 175.300, 21 CFR 175.320, 21 CFR 176.170, 21 CFR 176.180, 21 CFR 177.1200, 21 CFR 177.1390, 21 CFR 177.1500, 21 CFR 177.1630, 21 CFR 177.1680, 21 CFR 177.2420, 21 CFR 177.2600)
  • European Union Citations - Decision 1999/217/EC - Flavoing Substance; Directive 95/2/EC, Annex IV - Permitted Food Additive; 2002/72/EC, Annex A - Authorized monomer for Food Contact Plastics

External links

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