Acetoacetic acid
| Acetoacetic acid | |
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3-oxobutanoic acid, diacetic acid |
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| Identifiers | |
| CAS number | 541-50-4  |
| PubChem | 96 |
| ChemSpider | 94 |
| DrugBank | DB04025 |
| KEGG | C00164 |
| ChEBI | CHEBI:15344 |
| ChEMBL | CHEMBL1230762  |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C4H6O3 |
| Molar mass | 102.09 g/mol |
| Melting point |
36.5 °C |
| Boiling point |
Decomposes |
| Acidity (pKa) | 3.58 [1] |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Acetoacetic acid (also called 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]
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Synthesis and properties [edit]
In general, the esters are prepared by 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 50 times more slowly.[5]
It is a weak acid (like most alkyl carboxylic acids) with a pKa of 3.77.
Detection [edit]
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 [edit]
References [edit]
- ^ Dawson, R. M. C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
- ^ a b Franz Dietrich Klingler, Wolfgang Ebertz "Oxocarboxylic Acids" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a18 313
- ^ Robert C. Krueger (1952). "Crystalline Acetoacetic Acid". Journal of the American Chemical Society 74 (21): 5536–5536. doi:10.1021/ja01141a521.
- ^ 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
- ^ Hay, R. W.; Bond, M. A. (1967). "Kinetics of decarboxilation of acetoacetic acid". Aust. J. Chem. 20 (9): 1823–8. doi:10.1071/CH9671823.
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