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| 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 | |
| |
3D model (JSmol) | |
| 1209788 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| ECHA InfoCard | 100.004.250 |
| EC Number |
|
| E number | E355(antioxidants, ...) |
| 3166 | |
| KEGG |
|
| RTECS number |
|
| UNII | |
| UN number | 3077 |
| |
| |
| Properties | |
| 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) |
| 14 g/L (10 °C) 24 g/L (25 °C) 1600 g/L (100 °C) | |
| Solubility | Very soluble inmethanol,ethanol soluble inacetone,acetic acid slightly soluble incyclohexane negligible inbenzene,petroleum ether |
| logP | 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 | |
| Monoclinic | |
| Thermochemistry | |
Std enthalpy of formation(ΔfH⦵298) | −994.3 kJ/mol[3] |
| Hazards | |
| GHS labelling: | |
 | |
| Warning | |
| H319 | |
| P264,P280,P305+P351+P338,P337+P313 | |
| NFPA 704 (fire diamond) | |
| Flash point | 196 °C (385 °F; 469 K) |
| 422 °C (792 °F; 695 K) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 3600 mg/kg (rat) |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Relateddicarboxylic 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 theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Adipic acid orhexanedioic acid is anorganic compound with thechemical formula C6H10O4.[4] It is a white crystalline powder at standard temperature and pressure.[4] From an industrial perspective, it is the most importantdicarboxylic acid at about 2.5 billion kilograms produced annually, mainly as a precursor for the production ofnylon.[4] Adipic acid otherwise rarely occurs in nature,[5] but it is known as manufacturedE numberfood additiveE355.Salts andesters of adipic acid are known asadipates.
Adipic acid is produced by oxidation of a mixture ofcyclohexanone andcyclohexanol,[4] which is calledKA oil, an abbreviation of ketone-alcohol oil. Nitric acid is the oxidant. The pathway is multistep. Early in the reaction, the cyclohexanol is converted to theketone, releasingnitrous acid:
The cyclohexanone is then nitrosated, setting the stage for the scission of the C-C bond:
Side products of the method includeglutaric andsuccinic acids. Nitrous oxide is produced in about one to one mole ratio to the adipic acid,[6] as well, via the intermediacy of anitrolic acid.[5]
Related processes start from cyclohexanol, which is obtained from thehydrogenation ofphenol.[5][7]
Several methods have been developed bycarbonylation ofbutadiene. For example, thehydrocarboxylation proceeds as follows:[5]
Another method is oxidative cleavage ofcyclohexene usinghydrogen peroxide.[8] The waste product is water.
Auguste Laurent discovered adipic acid in 1837[9][10] by oxidation of various fats withnitric acid viasebacic acid[11] and gave it the current name because of that (ultimately from Latinadeps,adipis – "animal fat"; cf.adipose tissue).
Adipic acid is adiprotic acid (it has two acidic groups). The pKa values for their successivedeprotonations are 4.41 and 5.41.[12]
With the carboxylate groups separated by fourmethylene groups, adipic acid is suited for intramolecular condensation reactions. Upon treatment withbarium hydroxide at elevated temperatures, it undergoesketonization to givecyclopentanone.[13]
About 60% of the 2.5 billion kg of adipic acid produced annually is used as monomer for the production ofnylon[14] by apolycondensation reaction withhexamethylene diamine formingnylon 66. Other major applications also involve polymers; it is a monomer for production ofpolyurethane and its esters areplasticizers, especially inPVC.[citation needed]
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 ofhydrophilic 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.[15]
Small but significant amounts of adipic acid are used as a food ingredient as aflavorant andgelling aid.[16] It is used in somecalcium carbonateantacids to make themtart. As anacidulant inbaking powders, it avoids the undesirablehygroscopic properties oftartaric acid.[2] Adipic acid, rare in nature, does occur naturally inbeets, but this is not an economical source for commerce compared to industrial synthesis.[17]
Adipic acid, like most carboxylic acids, is a mild skin irritant. It is mildly toxic, with amedian lethal dose of 3600 mg/kg for oral ingestion by rats.[5]
The production of adipic acid is linked to emissions ofN
2O,[18] a potentgreenhouse gas and cause ofstratospheric ozone depletion. At adipic acid producersDuPont andRhodia (nowInvista andSolvay, respectively), processes have been implemented to catalytically convert the nitrous oxide to innocuous products:[19]
The anionic (HO2C(CH2)4CO2−) and dianionic (−O2C(CH2)4CO2−) forms of adipic acid are referred to asadipates. An adipate compound is acarboxylate salt orester of the acid.
Some adipate salts are used asacidity regulators, including:
Some adipate esters are used asplasticizers, including:
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