|Jmol-3D images||Image 1
|Molar mass||146.14 g mol−1|
|Appearance||White crystals |
|Melting point||152.1 °C (305.8 °F; 425.2 K)|
|Boiling point||337.5 °C (639.5 °F; 610.6 K)|
|Solubility in water||1.4 g/100 mL (10 °C)
2.4 g/100 mL (25 °C)
160 g/100 mL (100 °C)
|Solubility||very soluble in methanol, ethanol
soluble in acetone
slightly soluble in cyclohexane
negligible in benzene, petroleum ether
insoluble in acetic acid
|Vapor pressure||0.0728 Pa (18.5 °C)|
|Acidity (pKa)||4.43, 5.41|
|Viscosity||4.54 cP (160 °C)|
Std enthalpy of
|EU classification||Irritant (Xi)|
|Flash point||196 °C (385 °F; 469 K)|
|Autoignition temperature||422 °C (792 °F; 695 K)|
|LD50||3600 mg/kg (rat)|
|Related dicarboxylic acids||glutaric acid
|Related compounds||hexanoic acid
adipic acid dihydrazide
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Adipic acid is the organic compound with the formula (CH2)4(COOH)2. From an 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.
Preparation and reactivity
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+
Alternative methods of production
- CH2=CHCH=CH2 + 2 CO + 2 H2O → HO2C(CH2)4CO2H
A method 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. The waste product is water.
Historically, adipic acid was prepared by oxidation of various fats, thus the name (ultimately from Latin adeps, adipis : 'animal fat'; cf. adipose tissue).
With the carboxylate groups separated by four methylene groups, adipic acid is suited for intramolecular condensation reactions. Upon treatment with barium hydroxide at elevated temperatures, it undergoes ketonization to give cyclopentanone.
The great 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.
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.
The production of adipic acid is linked to emissions of N
2O, a potent greenhouse gas and cause of stratospheric ozone depletion. At adipic acid producers du Pont and Rhodia, processes have been implemented to catalytically convert the nitrous oxide to innocuous products:
- 2 N2O → 2 N2 + O2
- Musser, M. T. (2005), "Adipic Acid", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a01_269.
- B. A. Ellis (1925), "Adipic Acid", Org. Synth. 5: 9; Coll. Vol. 1: 560.
- 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.
- Ince, Walter (1895). "Preparation of adipic acid and some of its derivatives". Journal Chemical Society, London 67. doi:10.1039/CT8956700155. Retrieved 27 September 2012.
- Boy Cornils, Peter Lappe "Dicarboxylic Acids, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a08_523
- J. F. Thorpe and G. A. R. Kon (1925), "Cyclopentanone", Org. Synth. 5: 37; Coll. Vol. 1: 192.
- Roew, Raymond (2009), "Adipic Acid", Handbook of Pharmaceutical Excipients, pp. 11–12
- "Cherry Jell-O Nutrition Facts". Kraft Foods. Retrieved 21 Mar 2012.
- US EPA. "U.S. Greenhouse Gas Inventory Report, Chapter 4. Industrial Processes". Retrieved 2013-11-29.
- R. A. Reimer, C. S. Slaten, M. Seapan, T. A. Koch, V. G. Triner "Adipic Acid Industry — N2O Abatement" in Non-CO2 Greenhouse Gases: Scientific Understanding, Control and Implementation, Springer, Netherlands, 2000, pp 347-358. doi:10.1007/978-94-015-9343-4_56
- 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