Acetoacetic acid 81668 220050339 2008-06-18T01:34:31Z DOI bot 6652755 Citation maintenance. Initiated by [[User:Fconaway|Fconaway]]. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Chembox new | Name = Acetoacetic acid | ImageFile = Acetoacetic acid.png | ImageFile1 = Acetoacetic-acid-3D-balls.png | IUPACName = 3-oxobutanoic acid, diacetic acid | Section1 = {{Chembox Identifiers | CASNo = 541-50-4 | SMILES = CC(=O)CC(O)=O }} | Section2 = {{Chembox Properties | Formula = C<sub>4</sub>H<sub>6</sub>O<sub>3</sub> | MolarMass = 102.09 g/mol | Density = | MeltingPt = 36.5 °C | BoilingPt = Decomposes }} }} '''Acetoacetic acid''' is the [[organic compound]] with the formula CH<sub><font size="-1">3</font></sub>C(O)CH<sub><font size="-1">2</font></sub>CO<sub><font size="-1">2</font></sub>H. It is the simplest beta-[[keto acid]] group and like other members of this class is unstable. ==Synthesis and properties== Acetoacetic acid is a weak acid (like most alkyl carboxylic acids) with a pK<sub>a</sub> of 3.77. It can be prepared by the hydrolysis of the [[ethyl acetoacetate]] followed by acidification of the anion.<ref>{{cite journal | author = Robert C. Krueger | title = Crystalline Acetoacetic Acid | journal = Journal of the American Chemical Society | year = 1952 | volume = 74 | issue = 21 | pages = 5536–5536 | doi = 10.1021/ja01141a521 }} </ref> In general, acetoacetic acid is generated at 0 °C and used in situ immediately.<ref>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</ref> It decomposes at a moderate [[reaction rate|rate]] to [[acetone]] and [[carbon dioxide]]: :CH<sub>3</sub>C(O)CH<sub>2</sub>CO<sub>2</sub>H → CH<sub>3</sub>C(O)CH<sub>3</sub> + CO<sub>2</sub> The acid form has a [[half-life]] of 140 minutes at 37º 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.<ref>{{cite journal |author= Hay, R. W.; Bond, M. A.|year= 1967|title= Kinetics of decarboxilation of acetoacetic acid|journal= Aust. J. Chem.|volume = 20|issue=9|pages=1823–8}}</ref> ==Biochemistry== Acetoacetate is produced in the human [[liver]] under certain metabolic conditions such as during [[fatty acid]] breakdown. It is then partially converted to acetone by spontaneous [[decarboxylation]] and excreted either in urine or through respiration. The acid is also present in the metabolism of those undergoing starvation or prolonged physical exertion.There is no known pathway for acetoacetate to be converted into glucose. Acetoacetic acid is not the major ketone produced by the body, that being [[beta-hydroxybutyrate]]. ==Detection== When [[ketone bodies]] are measured by way of urine concentration, acetoacetic acid, along with [[beta-hydroxybutyrate|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 acid|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. ==See also== * [[3-hydroxybutyrate dehydrogenase]] ==References== {{reflist}} [[Category:Carboxylic acids]] [[Category:Ketones]] [[cs:Kyselina acetyloctová]] [[da:Acetoacetat]] [[de:Acetessigsäure]] [[fr:Acide acétylacétique]] [[lv:Acetoetiķskābe]] [[ja:アセト酢酸]] [[pl:Kwas acetylooctowy]]