Meconic acid

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Structural formula
Structural formula of meconic acid
General
Surname Meconic acid
other names
  • 3-Hydroxy-4-oxo-4 H -pyran-2,6-dicarboxylic acid ( IUPAC )
  • Acidum Meconicum
  • Poppy Acid
Molecular formula C 7 H 4 O 7
Brief description

colorless needles, leaflets, or scales

External identifiers / databases
CAS number 497-59-6
EC number 207-848-2
ECHA InfoCard 100.007.136
PubChem 10347
Wikidata Q421116
properties
Molar mass 200.10 g mol −1
Physical state

firmly

Melting point

120 ° C  (decomposition)

pK s value
  • pK s 1 1.83
  • pK s 2 2.11
solubility
safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Meconic acid , also called Acidum Meconicum , is a chemical compound from the pyrone group , which is contained in some poppy plants ( Papaveraceae ), for example in opium poppy ( Papaver somniferum ) and medicinal poppy ( Papaver bracteatum ). The compound is one of the constituents of opium with 4–6% (mekón = Greek poppy seed capsule) and can therefore be used to detect opium.

Opium poppy, Papaver somniferum , from whose milk opium can be obtained.
Milky juice of Papaver somniferum obtained by scratching immature seed pods provides opium when dried.

Meconic acid was erroneously described as having a narcotic effect, although it shows little or no pharmacological effect and is also not used medicinally. The pyrone forms salts with alkaloids and metals , the meconates . The French chemist Armand Seguin had progressed so far with his experiments by 1804 that he could produce meconic acid, but without knowing whether it was a specific acid or a mixture contaminated with vegetable components. Meconic acid was isolated for the first time in 1805 by Friedrich Sertürner .

properties

Meconic acid is a dicarboxylic acid ; it is a strong acid with a pK s 1 value of 1.83 and pK s 2 of 2.11. Its structure contains two carboxy groups (-COOH) and a hydroxyl group (-OH), which are located on a pyrone ring. This OH group is weakly acidic with a pKa value of 11.3. The substance is colorless and only slightly soluble in water and methanol , better in ethanol and benzene . Crystallization from aqueous solution leads to a trihydrate that forms orthorhombic platelets. When heated, meconic acid gradually decomposes, with comenic acid being formed by simple decarboxylation at temperatures above 200 ° C. Meconic acid shows - like some phenols and phenolic acids - a red color when reacting with iron (III) chloride and is used for the titrimetric detection of Fe (III) ions.

literature

Individual evidence

  1. ^ Friedrich Philipp Dulk: The Prussian Pharmacopoeia: Simple means. Voss; 1833, p. 761 ( limited preview in Google Book search).
  2. a b David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-296.
  3. a b c d e f g Alan Townshend: Dictionary of analytical reagents. Chapman & Hall / CRC Press, 1993, ISBN 0-412-35150-1 , p. 595.
  4. ) Entry on meconic acid in the ChemIDplus database of the United States National Library of Medicine (NLM) .
  5. This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  6. a b Entry on Meconic Acid. In: Römpp Online . Georg Thieme Verlag, accessed on May 3, 2019.
  7. James R. Partington: A History of Chemistry , Volume 3, Macmillan, London et al. 1962 (reprinted 1970), p. 107.
  8. Friedrich Sertuerner: About morphine, a new saline base, and meconic acid, as the main constituent parts of opium. Annalen der Physik , 1817 , 55 , pp. 56-89.
  9. Ryan J. Huxtable, Stephan KW Schwarz: The Isolation of Morphine - First Principles in Science and Ethics .
  10. Acidum Meconicum (Henriette's Herbal Homepage)
  11. AM Pictet: The plant alkaline and its chemical constitution. BiblioBazaar, 2009, ISBN 978-1-110-11341-5 ( limited preview in Google book search).