Acetoacetic acid
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| Names | |
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| IUPAC name
3-oxobutanoic acid, diacetic acid
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| Identifiers | |
541-50-4  |
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| ChEBI | CHEBI:15344 |
| ChEMBL | ChEMBL1230762  |
| ChemSpider | 94 |
| DrugBank | DB01762 |
| Jmol 3D model | Interactive image |
| KEGG | C00164 |
| PubChem | 96 |
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| Properties | |
| C4H6O3 | |
| Molar mass | 102.088 g/mol |
| Appearance | colorless, oily liquid |
| Melting point | 36.5 °C (97.7 °F; 309.6 K) |
| Boiling point | Decomposes |
| soluble | |
| Solubility | soluble in ethanol, ether |
| Acidity (pKa) | 3.58 [1] |
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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 | |
Acetoacetic acid (also diacetic acid) is the organic compound with the formula CH3COCH2COOH. It is the simplest beta-keto acid group and like other members of this class is unstable. The methyl and ethyl esters, which are quite stable, are produced on a large scale industrially as precursors to dyes.[2]
Synthesis and properties
In general, the esters are prepared from diketene by treatment with alcohols.[2] Acetoacetic acid can be prepared by the hydrolysis of the ethyl acetoacetate followed by acidification of the anion.[3] In general, acetoacetic acid is generated at 0 °C and used in situ immediately.[4] It decomposes at a moderate rate to acetone and carbon dioxide:
- CH3C(O)CH2CO2H → CH3C(O)CH3 + CO2
The acid form has a half-life of 140 minutes at 37 °C in water, whereas the basic form (the anion) has a half-life of 130 hours. That is, it reacts about 55 times more slowly.[5]
It is a weak acid (like most alkyl carboxylic acids) with a pKa of 3.58.
Applications
Acetoacetic esters are used for the acetoacetylation reaction, which is widely used in the production of arylide yellows and diarylide dyes.[2] Although the esters can be used in this reaction, diketene also reacts with alcohols and amines to the corresponding acetoacetic acid derivatives in a process called acetoacetylation. An example is the reaction with 2-aminoindane:[6]
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Detection
When ketone bodies are measured by way of urine concentration, acetoacetic acid, along with beta-hydroxybutyric acid (BHB), and acetone, is what is detected. This is done using dipsticks coated in nitroprusside or similar reagents. Nitroprusside changes from pink to purple in the presence of acetoacetate, the conjugate base of acetoacetic acid, and the colour change is graded by eye. The popular dipstick used to detect ketone bodies in urine "Ketostix" by Bayer, only detects acetoacetate, not BHB or acetone.[citation needed]
See also
References
- ↑ Dawson, R. M. C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
- ↑ 2.0 2.1 2.2 Franz Dietrich Klingler, Wolfgang Ebertz "Oxocarboxylic Acids" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a18 313
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ George A. Reynolds and J. A. VanAllan "Methylglyoxal-ω-Phenylhydrazone" Organic Syntheses, Collected Volume 4, p.633 (1963).http://www.orgsyn.org/orgsyn/pdfs/CV4P0633.pdf
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
