Croconic acid

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Structural formula
Structural formula of croconic acid
General
Surname Croconic acid
other names
  • 4,5-dihydroxy-4-cyclopentene-1,2,3-trione
  • Croconic acid
Molecular formula C 5 H 2 O 5
Brief description

odorless dark yellow solid

External identifiers / databases
CAS number 488-86-8
ECHA InfoCard 100.201.686
PubChem 546874
Wikidata Q746380
properties
Molar mass 142.07 g mol −1
Physical state

firmly

Melting point

> 300 ° C

solubility

soluble in water and ethanol

safety instructions
GHS labeling of hazardous substances
07 - Warning

Caution

H and P phrases H: 315-319-335
P: 280-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Croconic acid is an organic chemical compound from the group of oxocarbons .

Extraction and presentation

In a work from 1825, Leopold Gmelin describes a saffron yellow, acidic substance that he observes in the preparation of potassium using a method developed by Carl Emanuel Brunner by glowing potash with charcoal and which he calls croconic acid. He observed, like Friedrich Wöhler and Jöns Jakob Berzelius before him, the formation of a dark gray, viscous mass. From this he obtained orange needle-shaped crystals of an unknown potassium salt by cleaning, which he called "croconic potash" because of its yellow color, derived from the Greek word χροχον for saffron and egg yolk. Gmelin then obtained croconic acid from the compound known today as potassium croconate by reacting it with anhydrous alcohol and sulfuric acid. In 1843 he created the correct empirical formula K 2 (CO) 5 for croconic potassium . But only Rudolf Nietzki was able to determine the cyclic and quinoid form of croconic acid. This makes croconic acid the first synthesized cyclic carbonyl compound that was obtained from purely inorganic starting materials.

properties

Croconic acid is a dark yellow ferroelectric solid that is soluble in water and ethanol . The compound oxidizes in acidic media to form oxalic acid and mesoxalic acid . It is a strong acid and is sensitive to sunlight. In the solid state, croconic acid has a special structure made up of strips, with each “side” of the strip being a planar ring of four molecules held together by hydrogen bonds. It has a different structure in aqueous solution. It has an orthorhombic crystal structure with the space group Pca 2 1 (space group no. 29) . Template: room group / 29

use

Croconic acid is used to produce 1,3-bis- (2-dimethylamino-5-thienyl) croconine by reacting with dimethylthiophen-2- ylamine . It is also used in organic synthesis and as a dye for biological research purposes. It is also involved in the manufacture of ethers such as dimethyl croconate. In addition, it acts as a ligand and forms coordination complexes with metals such as barium , copper , silver and lead . A high-pressure variant of the connection is being investigated as a possible explosive.

Individual evidence

  1. ↑ a b c d e f data sheet Croconic acid, 98% from AlfaAesar, accessed on September 13, 2018 ( PDF )(JavaScript required) .
  2. ↑ a b c data sheet Croconic acid, 98% from Sigma-Aldrich , accessed on September 13, 2018 ( PDF ).
  3. ^ A b Sieghard Neufeldt: Chronology of chemistry, discoverers and discoveries . John Wiley & Sons, 2012, ISBN 3-527-66284-7 , pp. 21 ( limited preview in Google Book search).
  4. ↑ Petra Stumm: Leopold Gmelin (1788 - 1853) life and work of a Heidelberg chemist . Springer-Verlag, 2016, ISBN 978-3-86226-844-3 , p. 135 ( limited preview in Google Book search).
  5. ^ A b Sanghamitra Mukhopadhyay, Matthias Gutmann, Felix Fernandez-Alonso: Hydrogen-bond structure and anharmonicity in croconic acid. In: Phys. Chem. Chem. Phys. 16, 2014, p. 26234, doi : 10.1039 / C4CP03713H .
  6. ^ Paul-Louis Fabre, Paule Castan, Diane Deguenon, Nicole Paillous: A photo-oxidation of croconic acid into oxalic acid. In: Canadian Journal of Chemistry. 73, 1995, p. 1298, doi : 10.1139 / v95-160 .
  7. ↑ a b Kiyoyuki Yamada, Nobuhisa Mizuno, Yoshimasa Hirata: Structure of Croconic Acid. In: Bulletin of the Chemical Society of Japan. 31, 1958, p. 543, doi : 10.1246 / bcsj.31.543 .
  8. ↑ Dario Braga, Lucia Maini, Fabrizia Grepioni: Croconic Acid and Alkali Metal Croconate Salts: Some New Insights into an Old Story. In: Chemistry - A European Journal. 8, p. 1804, doi : 10.1002 / 1521-3765 (20020415) 8: 8 <1804 :: AID-CHEM1804> 3.0.CO; 2-C .
  9. ↑ Google Patents: US20170066706A1 - Energetic high pressure polymorph of croconic acid and high energy compositions formed therefrom - Google Patents , accessed September 13, 2018