Adipic acid

Adipic acid
Names
	Preferred IUPAC name Hexanedioic acid
	Other names Adipic acid; Butane-1,4-dicarboxylic acid; Hexane-1,6-dioic acid; 1,4-butanedicarboxylic acid
Identifiers
CAS Number	124-04-9 ;
3D model (JSmol)	Interactive image; Interactive image;
Beilstein Reference	1209788
ChEBI	CHEBI:30832 ;
ChEMBL	ChEMBL1157 ;
ChemSpider	191 ;
ECHA InfoCard	100.004.250
EC Number	204-673-3;
E number	E355 (antioxidants, ...)
Gmelin Reference	3166
KEGG	D08839 ;
PubChem CID	196;
RTECS number	AU8400000;
UNII	76A0JE0FKJ ;
UN number	3077
CompTox Dashboard (EPA)	DTXSID7021605 ;
	InChI InChI=1S/C6H10O4/c7-5(8)3-1-2-4-6(9)10/h1-4H2,(H,7,8)(H,9,10) Key: WNLRTRBMVRJNCN-UHFFFAOYSA-N ; InChI=1/C6H10O4/c7-5(8)3-1-2-4-6(9)10/h1-4H2,(H,7,8)(H,9,10) Key: WNLRTRBMVRJNCN-UHFFFAOYAY;
	SMILES O=C(O)CCCCC(=O)O; C(CCC(=O)O)CC(=O)O;
Properties
Chemical formula	C6H10O4
Molar mass	146.142 g·mol−1
Appearance	White crystals[1]; Monoclinic prisms[2]
Odor	Odorless
Density	1.360 g/cm3
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	14 g/L (10 °C) ; 24 g/L (25 °C) ; 1600 g/L (100 °C)
Solubility	Very soluble in methanol, ethanol ; soluble in acetone ; slightly soluble in cyclohexane ; negligible in benzene, petroleum ether ; insoluble in acetic acid
log P	0.08
Vapor pressure	0.097 hPa (18.5 °C) = 0.073 mmHg
Acidity (pKa)	4.43, 5.41
Conjugate base	Adipate
Viscosity	4.54 cP (160 °C)
Structure
Crystal structure	Monoclinic
Thermochemistry
Std enthalpy of; formation (ΔfH⦵298)	−994.3 kJ/mol[3]
Hazards
Safety data sheet	External MSDS
GHS pictograms
GHS Signal word	Warning
GHS hazard statements	H319
GHS precautionary statements	P264, P280, P305+351+338, P337+313
NFPA 704 (fire diamond)	1 2 0
Flash point	196 °C (385 °F; 469 K)
Autoignition; temperature	422 °C (792 °F; 695 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	3600 mg/kg (rat)
Related compounds
Related dicarboxylic acids	glutaric acid; pimelic acid
Related compounds	hexanoic acid; adipic acid dihydrazide; hexanedioyl dichloride; hexanedinitrile; hexanediamide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Adipic acid or hexanedioic 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,[4] but it is known as manufactured E number food additive E355.

Preparation and reactivity

Adipic acid is produced from a mixture of cyclohexanone and cyclohexanol 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 → OC(CH₂)₅ + 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. Nitrous oxide is produced in about one to one mole ratio to the adipic acid,[5] as well, via the intermediacy of a nitrolic acid.[4]

Related processes start from cyclohexanol, which is obtained from the hydrogenation of phenol.[4][6]

Alternative methods of production

Several methods have been developed by carbonylation of butadiene. For example, the hydrocarboxylation proceeds as follows:[4]

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

Another method is oxidative cleavage of cyclohexene using hydrogen peroxide.[7] The waste product is water.

Historically, adipic acid was prepared by oxidation of various fats,[8] thus the name (ultimately from Latin adeps, adipis – "animal fat"; cf. adipose tissue).

Reactions

Adipic acid is a dibasic acid (it has two acidic groups). The pK_a values for their successive deprotonations are 4.41 and 5.41.[9]

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.[10]

Uses

About 60% of the 2.5 billion kg of adipic acid produced annually is used as monomer for the production of nylon [11] by a polycondensation reaction with hexamethylene diamine forming nylon 66. 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.[12]

In foods

Small but significant amounts of adipic acid are used as a food ingredient as a flavorant and gelling aid.[13] It is used in some calcium carbonate antacids to make them tart. As an acidulant in baking powders, it avoids the undesirable hygroscopic properties of tartaric acid.[2] Adipic acid, rare in nature, does occur naturally in beets, but this is not an economical source for commerce compared to industrial synthesis.[14]

Safety

Adipic acid, like most carboxylic acids, is a mild skin irritant. It is mildly toxic, with a median lethal dose of 3600 mg/kg for oral ingestion by rats.[4]

Environmental

The production of adipic acid is linked to emissions of N
₂O,[15] a potent greenhouse gas and cause of stratospheric ozone depletion. At adipic acid producers DuPont and Rhodia (now Invista and Solvay, respectively), processes have been implemented to catalytically convert the nitrous oxide to innocuous products:[16]

2 N₂O → 2 N₂ + O₂

References

Mac Gillavry, C. H. (2010). "The crystal structure of adipic acid". Recueil des Travaux Chimiques des Pays-Bas. 60 (8): 605–617. doi:10.1002/recl.19410600805.
"Adipic Acid". The Merck Index. Royal Society of Chemistry. 2013. Retrieved 2 March 2017.
Haynes, W. M., ed. (2013). CRC Handbook of Chemistry and Physics (94th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4665-7114-3.
Musser, M. T. (2005). "Adipic Acid". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_269. ISBN 3527306730.
Parmon, V. N.; Panov, G. I.; Uriarte, A.; Noskov, A. S. (2005). "Nitrous oxide in oxidation chemistry and catalysis application and production". Catalysis Today. 100 (2005): 115–131. doi:10.1016/j.cattod.2004.12.012.
Ellis, B. A. (1925). "Adipic Acid". Organic Syntheses. 5: 9.; Collective Volume, 1, p. 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. Bibcode:1998Sci...281.1646S. doi:10.1126/science.281.5383.1646. PMID 9733504.
Ince, Walter (1895). "Preparation of adipic acid and some of its derivatives". Journal of the Chemical Society, Transactions. 67: 155–159. doi:10.1039/CT8956700155.
Cornils, Boy; Lappe, Peter (2000). "Dicarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_523.
Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Organic Syntheses. 5: 37.; Collective Volume, 1, p. 192
"Archived copy". Archived from the original on 2015-05-18. Retrieved 2015-05-09.CS1 maint: archived copy as title (link) PCI abstract for adipic acid
Roew, Raymond (2009), "Adipic Acid", Handbook of Pharmaceutical Excipients, pp. 11–12
"Cherry Jell-O Nutrition Facts". Kraft Foods. Retrieved 21 Mar 2012.
American Chemical Society (9 February 2015). "Molecule of the Week: Adipic Acid".
US EPA. "U.S. Greenhouse Gas Inventory Report, Chapter 4. Industrial Processes" (PDF). Retrieved 2013-11-29.
Reimer, R. A.; Slaten, C. S.; Seapan, M.; Koch, T. A.; Triner, V. G. (2000). "Adipic Acid Industry — N₂O Abatement". Non-CO₂ Greenhouse Gases: Scientific Understanding, Control and Implementation. Netherlands: Springer. pp. 347–358. doi:10.1007/978-94-015-9343-4_56. ISBN 978-94-015-9343-4.

Appendix

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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[1] Mac Gillavry, C. H. (2010). "The crystal structure of adipic acid". Recueil des Travaux Chimiques des Pays-Bas. 60 (8): 605–617. doi:10.1002/recl.19410600805.

[Adipic_Acid-2] "Adipic Acid". The Merck Index. Royal Society of Chemistry. 2013. Retrieved 2 March 2017.

[crc-3] Haynes, W. M., ed. (2013). CRC Handbook of Chemistry and Physics (94th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4665-7114-3.

[Ullmann-4] Musser, M. T. (2005). "Adipic Acid". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_269. ISBN 3527306730.

[CatalysisToday2005-5] Parmon, V. N.; Panov, G. I.; Uriarte, A.; Noskov, A. S. (2005). "Nitrous oxide in oxidation chemistry and catalysis application and production". Catalysis Today. 100 (2005): 115–131. doi:10.1016/j.cattod.2004.12.012.

[6] Ellis, B. A. (1925). "Adipic Acid". Organic Syntheses. 5: 9.; Collective Volume, 1, p. 560

[7] 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. Bibcode:1998Sci...281.1646S. doi:10.1126/science.281.5383.1646. PMID 9733504.

[8] Ince, Walter (1895). "Preparation of adipic acid and some of its derivatives". Journal of the Chemical Society, Transactions. 67: 155–159. doi:10.1039/CT8956700155.

[Ullmanns-9] Cornils, Boy; Lappe, Peter (2000). "Dicarboxylic Acids, Aliphatic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_523.

[10] Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Organic Syntheses. 5: 37.; Collective Volume, 1, p. 192

[11] "Archived copy". Archived from the original on 2015-05-18. Retrieved 2015-05-09.CS1 maint: archived copy as title (link) PCI abstract for adipic acid

[12] Roew, Raymond (2009), "Adipic Acid", Handbook of Pharmaceutical Excipients, pp. 11–12

[13] "Cherry Jell-O Nutrition Facts". Kraft Foods. Retrieved 21 Mar 2012.

[14] American Chemical Society (9 February 2015). "Molecule of the Week: Adipic Acid".

[15] US EPA. "U.S. Greenhouse Gas Inventory Report, Chapter 4. Industrial Processes" (PDF). Retrieved 2013-11-29.

[16] Reimer, R. A.; Slaten, C. S.; Seapan, M.; Koch, T. A.; Triner, V. G. (2000). "Adipic Acid Industry — N₂O Abatement". Non-CO₂ Greenhouse Gases: Scientific Understanding, Control and Implementation. Netherlands: Springer. pp. 347–358. doi:10.1007/978-94-015-9343-4_56. ISBN 978-94-015-9343-4.