488-86-8

Basic information

• Product Name: CROCONIC ACID
• Synonyms: Croconicacid,98%;1,2-Dihydroxycyclopentene-3,4,5-trione;Crocic acid;4,5-Dihydroxy-4-cyclopentene-1,2,3-trione,97%;4-Cyclopentene-1,2,3-trione,4,5-dihydroxy-;4-Cyclopentene-1,2,3-trione;4,5-DIHYDROXY-4-CYCLOPENTENE-1,2,3-TRIONE;4,5-DIHYDROXY-CYCLOPENT-4-ENE-1,2,3-TRIONE
• CAS NO: 488-86-8
• Molecular Formula: C₅H₂O₅
• Molecular Weight: 142.07
• Mol File: 488-86-8.mol
• Article Data: 3

Chemical Properties

• Melting Point: >300 °C(lit.)
• Boiling Point: 291.7°C
• Flash Point: 144.4 °C
• Appearance: Yellow/Powder or Crystals
• Density: 2.3110
• Vapor Pressure: 1.98E-06mmHg at 25°C
• Refractive Index: 1.6400 (estimate)
• Storage Temp.: room temp
• PKA: 0.92±0.25(Predicted)
• Water Solubility: Soluble in water and ethanol.
• Stability: Stable. Incompatible with strong oxidizing agents.
• BRN: 2043130
• CAS DataBase Reference: CROCONIC ACID(CAS DataBase Reference)
• NIST Chemistry Reference: CROCONIC ACID(488-86-8)
• EPA Substance Registry System: CROCONIC ACID(488-86-8)

Safety Data

• Hazard Codes: Xi
• Statements: 36/37/38
• Safety Statements: 37/39-26-24/25
• WGK Germany: 3
• Hazardous Substances Data: 488-86-8(Hazardous Substances Data)

Usage

Chemical Properties

gold-coloured powder

Uses

Croconic acid is used to prepare 1,3-bis-(2-dimethylamino-5-thienyl)croconine by reacting with dimethyl-thiophen-2-yl-amine. It is also used in organic synthesis and employed as a dye for biological research purposes. Further, it is involved in the preparation of ethers such as dimethyl croconate. In addition to this, it acts as a ligand and form coordination complexes with metals such as barium, copper, silver and lead.

InChI:InChI=1/C5H2O5/c6-1-2(7)4(9)5(10)3(1)8/h1,6H

Synthetic route

maleic anhydride (930-60-9) → croconic acid (488-86-8)

Conditions	Yield
Stage #1: maleic anhydride With sodium hydroxide; bromine In water at 0 - 20℃; for 1.66667h; Stage #2: With hydrogenchloride In water at 0℃; Product distribution / selectivity;	88%
Stage #1: maleic anhydride With water; chlorine; potassium carbonate at 0 - 50℃; for 6h; Stage #2: With hydrogenchloride at 10℃; Product distribution / selectivity;	66%

cyclopentene (142-29-0) → croconic acid (488-86-8)

Conditions	Yield
Stage #1: cyclopentene With potassium hydroxide; bromine In water; benzene at 0 - 60℃; for 5h; Stage #2: With hydrogenchloride In water; benzene at 5℃; Product distribution / selectivity;	83%

ccyclopentane-1,2,4-trione (15849-14-6) → croconic acid (488-86-8)

Conditions	Yield
Stage #1: ccyclopentane-1,2,4-trione With 1,3-dichloro-5,5-dimethylhydantoin In 1,2-dichloro-ethane at 0℃; for 2h; Stage #2: With sodium hydroxide In water; 1,2-dichloro-ethane at 0 - 50℃; for 4.5h; Stage #3: With hydrogenchloride In water; 1,2-dichloro-ethane at 0℃; Product distribution / selectivity;	63%

D-myo-inositol (87-89-8) → croconic acid (488-86-8)

Conditions	Yield
With nitric acid

sodium rhodizonate dibasic (523-21-7) → croconic acid (488-86-8) + hexaketocyclohexane (527-31-1)

Conditions	Yield
With oxygen In water Rate constant; Quantum yield; Irradiation; various pH;

tetrahydroxy-1,4-quinone (319-89-1) → croconic acid (488-86-8)

Conditions	Yield
With manganese(IV) oxide; potassium carbonate

rhodizonic acid (118-76-3) + alkali carbonate → croconic acid (488-86-8)

Conditions	Yield
Abdampfen an der Luft;

rhodizonic acid (118-76-3) + alkali → croconic acid (488-86-8)

Conditions	Yield
Abdampfen an der Luft;

dipotassium-salt of/the/ rhodizonic acid → croconic acid (488-86-8)

Conditions	Yield
With air; water at 80℃;

disodium-salt of tetrahydroxy-benzoquinone-(1.4) → croconic acid (488-86-8)

Conditions	Yield
With air; water at 80℃;

sodium-salt of rhodizonate of → croconic acid (488-86-8)

Conditions	Yield
With manganese(IV) oxide; potassium carbonate

D-myo-inositol (87-89-8) + nitric acid (7697-37-2) → benzenehexol (608-80-0) + croconic acid (488-86-8) + rhodizonic acid (118-76-3) + 2.3.5.6-tetrahydroxy-benzoquinone-1.4)

croconic acid dimethyl ether (36394-33-9) + water (7732-18-5) → croconic acid (488-86-8)

Conditions	Yield
beim Aufbewahren;

4,5-diethoxy-cyclopent-4-ene-1,2,3-trione (63183-46-0) + moist air → croconic acid (488-86-8)

cyclopentanedecaol (595-03-9) + reducing agent → croconic acid (488-86-8)

hydrogenchloride (7647-01-0) + 2,2,2',2'-tetraethoxy-5,5'-dimethoxy-4,4-ethanediyldiamino-bis-cyclopent-4-ene-1,3-dione → croconic acid (488-86-8)

4-ethoxy-5-hydroxy-cyclopent-4-ene-1,2,3-trione (854403-77-3) + water (7732-18-5) → croconic acid (488-86-8)

2,2-diethoxy-4,5-dihydroxy-cyclopent-4-ene-1,3-dione + water (7732-18-5) → croconic acid (488-86-8)

triaminophloroglucinol hydrogen sulfate (114491-15-5) + manganese dioxide + natrium carbonate → croconic acid (488-86-8)

3,6-diamino-benzene-1,2,4,5-tetraol; dihydrochloride (643-00-5) + potassium carbonate + manganese dioxide → croconic acid (488-86-8)

barium croconate → croconic acid (488-86-8)

Conditions	Yield
With sulfuric acid In water for 1h; warming;

croconic acid (488-86-8) + boric acid (11113-50-1) + 1,4-Dioxane-2,3,5,6-tetrone (213967-57-8) → Li(1+)*C7BO9(1-)

Conditions	Yield
In water at 20℃; under 0 Torr; for 8h; Flow reactor;	99.1%

croconic acid (488-86-8) + malononitrile (109-77-3) → 1,2,3-tris(dicyanomethylene)-4-cyclopentene-4,5-diol (72905-24-9)

Conditions	Yield
In water at 85 - 90℃; for 0.25h;	97%

croconic acid (488-86-8) + 2-methyl-1-phenyl-(1H)-benz[cd]indolium iodide → 2-[[2-hydroxy-3-[(1-phenylbenz[cd]indole-2(1H)-ylidene)methyl]-4,5-dioxo-2-cyclopentene-1-ylidene]methyl]-1-phenylbenzo[cd]indolium

Conditions	Yield
In toluene; butan-1-ol at 107℃; for 3h; Inert atmosphere;	94.8%

croconic acid (488-86-8) + C20H26N2 → C45H50N4O3

Conditions	Yield
In propan-1-ol; toluene for 2h; Reflux;	93%

croconic acid (488-86-8) + C23H27N → C51H52N2O3

Conditions	Yield
In toluene; butan-1-ol for 1h; Reflux;	91%

croconic acid (488-86-8) + 2,3,3-trimethyl-5-(4-nitrophenyl)-3H-indole → 3-[3,3-dimethyl-5-(4-nitrophenyl)-1,3-dihydro-indol-2-ylidenemethyl]-5-[3,3-dimethyl-5-(4-nitro-phenyl)-3H-indol-2-ylmethylene]-4-hydroxy-cyclopent-3-ene-1,2-dione

Conditions	Yield
In toluene; butan-1-ol at 110℃; for 3h; Dean-Stark;	87%

2,3,3-trimethylbenzo[e]indole (41532-84-7) + croconic acid (488-86-8) → 5-((1,1-dimethyl-1H-benzo[e]indol-3-ium-2-yl)methylene)-2-hydroxy-3,4-dioxocyclopent-1-enolate

Conditions	Yield
In water; acetone at 50℃; for 96h; Solvent; Temperature;	86%

croconic acid (488-86-8) + 6-bromo-N-methyl-2-quinaldinium iodide (59105-86-1) → C27H18Br2N2O3 (1005495-50-0)

Conditions	Yield
With quinoline In ethanol at 80℃; for 24h;	85%

croconic acid (488-86-8) + 6-iodo-N-methyl-2-quinaldinium iodide (10352-61-1) → C27H18I2N2O3 (1005495-52-2)

Conditions	Yield
With quinoline In ethanol at 80℃; for 24h;	85%

croconic acid (488-86-8) + 2-amino-5-hydroxybenzoic acid (394-31-0) → C19H12N2O9

Conditions	Yield
In methanol at 60℃;	85%

croconic acid (488-86-8) + 5-bromo-2-methyl-3-octyl-1,3-benzothiazol-3-ium iodide (100362-83-2) → 5-((5-cyano-3,3-dimethyl-3H-indol-1-ium-2-yl)methylene)-2-hydroxy-3,4-dioxocyclopent-1-enolate

Conditions	Yield
In water; acetone at 0 - 3℃; for 48h;	85%

croconic acid (488-86-8) + tetrabutylammomium bromide (1643-19-2) + iron(III) chloride (7705-08-0) → tetra-n-butylammonium tris(croconato)ferrate(III)

Conditions	Yield
With NaOH In water byproducts: NaCl, NaBr; NaOH and (C4H9)4NBr added to C5O3(OH)2*3H2O in H2O, FeCl3 added dropwise; extd. (CH2Cl2), anhyd. Na2SO4 added, filtered, evapd. (vac.), crystd. (MeOH/Et2O) for days; elem. anal.;	83%

croconic acid (488-86-8) + 1-(thiophen-2-yl)piperidine-4-carboxylic acid → C25H24N2O7S2

Conditions	Yield
In toluene; butan-1-ol for 1h; Reflux;	82%

croconic acid (488-86-8) + C17H17NO (1303477-72-6) → C39H32N2O5

Conditions	Yield
In toluene; butan-1-ol for 2h; Reflux;	81%

5-bromo-2,3,3-trimethyl-3H-indole (54136-24-2) + croconic acid (488-86-8) → 3-(5-bromo-3,3-dimethyl-1,3-dihydro-indol-2-ylidenemethyl)-5-(5-bromo-3,3-dimethyl-3H-indol-2-ylmethylene)-4-hydroxy-cyclopent-3-ene-1,2-dione

Conditions	Yield
In toluene; butan-1-ol at 110℃; for 3h; Dean-Stark;	80%

croconic acid (488-86-8) + 1-thiophen-2-yl-piperidine-4-carboxylic acid decylester → C45H64N2O7S2

Conditions	Yield
In toluene; butan-1-ol for 1h; Inert atmosphere; Reflux;	79.9%

croconic acid (488-86-8) → catena(triaqua-(μ-2-croconato-O,O',O",O"')calcium(II)) calcium croconate trihydrate

Conditions	Yield
With calcium acetate In water at 180℃; for 2h;	79%

croconic acid (488-86-8) + N-benzyl-N-[2-(prop-2-yn-1-yloxy)ethyl]thiophen-2-amine → C37H32N2O5S2

Conditions	Yield
In toluene; butan-1-ol for 1h; Inert atmosphere; Reflux;	79%

croconic acid (488-86-8) + 2-(N,N-dibutylamino)thiophene → (E)-2-(5-(dibutylamino)thiophen-2-yl)-5-(5-(dibutyliminio)thiophen-2(5H)-ylidene)-3,4-dioxocyclopent-1-en-1-olate

Conditions	Yield
In toluene; butan-1-ol Reflux;	78%

croconic acid (488-86-8) + 1,2-diamino-benzene (95-54-5) → 2,3-dihydroxy-1H-cyclopenta[b]quinoxalin-1-one (23774-23-4)

Conditions	Yield
With acetic acid at 40℃; for 2h; Inert atmosphere;	78%

2,3,3-trimethylindoleniune (1640-39-7) + croconic acid (488-86-8) → 3-[3,3-Dimethyl-1,3-dihydro-indol-(2E)-ylidenemethyl]-5-[1-(3,3-dimethyl-3H-indol-2-yl)-meth-(Z)-ylidene]-4-hydroxy-cyclopent-3-ene-1,2-dione

Conditions	Yield
In butan-1-ol; benzene Heating;	76%

croconic acid (488-86-8) + 2,6-di-tert-butyl-4-methylpyrilium hexafluorophosphate → 4-[(3-[(2,6-bis(1,1-dimethylethyl)-4H-pyran-4-ylidene)methyl]-2-hydroxy-4,5-dioxo-2-cyclopenten-1-ylidene)methyl]-2,6-bis(1,1-dimethylethyl)pyrylium inner salt

Conditions	Yield
With pyridine In methanol for 3h; Condensation; Heating;	75%

cholesteryl N-methyl-2-quinaldinium-6-yl carbonate iodide + croconic acid (488-86-8) → C83H108N2O9 (1005495-54-4)

Conditions	Yield
With quinoline In ethanol at 80℃; for 24h;	75%

croconic acid (488-86-8) + N-ethyl-N-(2-(prop-2-yn-1-yloxy)ethyl)thiophen-2-amine → C27H28N2O5S2

Conditions	Yield
In toluene; butan-1-ol for 1h; Inert atmosphere; Reflux;	74%

croconic acid (488-86-8) + iron(III) chloride (7705-08-0) + tetraphenylphosphonium bromide (2751-90-8) → tetraphenylphosphonium tris(croconato)ferrate(III)

Conditions	Yield
With NaOH In water NaOH and P(C6H5)4Br added to C5O3(OH)2*3H2O in H2O, FeCl3 added dropwise; extd. (CH2Cl2), anhyd. Na2SO4 added, filtered, evapd. (vac.), crystd. (MeOH/Et2O); elem. anal.;	72%

croconic acid (488-86-8) + 9-methyl-2,2',5,5'-tetra-tert-butyl-8H,8'H-7,7'-biacenaphthyleno[1,2-c]pyrrole → C93H94N4O3

Conditions	Yield
In toluene; butan-1-ol at 80℃; for 1h;	71%

1-(thiophen-2-yl)piperidine (19983-20-1) + croconic acid (488-86-8) → C23H24N2O3S2

Conditions	Yield
In toluene; butan-1-ol Heating;	70%

2,3,3-trimethyl-5-nitro-3H-indole (3484-22-8) + croconic acid (488-86-8) → 3-[3,3-Dimethyl-5-nitro-1,3-dihydro-indol-(2E)-ylidenemethyl]-5-[1-(3,3-dimethyl-5-nitro-3H-indol-2-yl)-meth-(Z)-ylidene]-4-hydroxy-cyclopent-3-ene-1,2-dione

Conditions	Yield
In butan-1-ol; benzene Heating;	70%

Upstream product

• 87-89-8 D-myo-inositol 
• 523-21-7 sodium rhodizonate dibasic 
• 319-89-1 tetrahydroxy-1,4-quinone 
• 118-76-3 rhodizonic acid 
• 7697-37-2 nitric acid 
• 36394-33-9 croconic acid dimethyl ether 
• 7732-18-5 water 
• 63183-46-0 4,5-diethoxy-cyclopent-4-ene-1,2,3-trione 
• 595-03-9 cyclopentanedecaol 
• 7647-01-0 hydrogenchloride 
• 854403-77-3 4-ethoxy-5-hydroxy-cyclopent-4-ene-1,2,3-trione 
• 114491-15-5 triaminophloroglucinol hydrogen sulfate 
• 643-00-5 3,6-diamino-benzene-1,2,4,5-tetraol; dihydrochloride 
• 142-29-0 cyclopentene 

Downstream Products

• 595-03-9 cyclopentanedecaol 
• 14379-01-2 cyclopentanepentaone tetraoxime 
• 124-38-9 carbon dioxide 
• 144-62-7 oxalic acid 
• 23774-25-6 Chinoxalino<2,3-d>cyclopentantrion-1,2,3 
• 23774-23-4 Chinoxalino<2.3-d>-2.3-dihydroxy-cyclopentadienon-1 
• 14379-00-1 croconic acid disodium salt 

Relevant articles and documents

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Process for producing croconic acid or salt thereof

Croconic acid or a salt thereof is easily produced at low cost by a reaction of a hydrocarbon compound consisting of a five-membered ring or a hydrocarbon compound consisting of a five-membered ring having an oxo group and/or a monovalent group linked via an oxygen atom with a halogenating agent.