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Squaric acid

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Products Intro: Product Name:3,4-DIHYDROXY-3-CYCLOBUTEN-1,2-DIONE
CAS:2892-51-5
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Squaric acid Basic information
Product Name:Squaric acid
Synonyms:4-dihydroxy-3-cyclobutene-1;3,4-Dihydroxy-3-cyclobuten-1,2-dion;3,4-Dihydroxy-3-cyclobutene-1,2-dione, 99% 25GR;3,4-Dihydroxy-3-cyclobutene-1,2-dione, 99% 5GR;dihydroxy-cyclobutenedion;dihydroxycyclobutenedione;3,4-DIHYDROXY-3-CYCLOBUTEN-1,2-DIONE;1-Cyclobutene-3,4-dione-1,2-diol Squaric Acid
CAS:2892-51-5
MF:C4H2O4
MW:114.06
EINECS:220-761-4
Product Categories:cyclic compounds;Organic acids;Ring Systems;Cyclobutanes & Cyclobutenes;Simple 4-Membered Ring Compounds
Mol File:2892-51-5.mol
Squaric acid Structure
Squaric acid Chemical Properties
Melting point >300 °C(lit.)
Boiling point 250.96°C
density 1.82 g/cm3
refractive index 1.5800 (estimate)
Fp 190 °C
storage temp. Inert atmosphere,Room Temperature
solubility 20g/l
pka1.5??(at 25℃)
form Crystalline Powder
color White to beige
PH1 (1g/l, H2O, 20℃)
Water Solubility 20 g/L (30 ºC)
Merck 14,8769
BRN 774275
InChIKeyPWEBUXCTKOWPCW-UHFFFAOYSA-N
CAS DataBase Reference2892-51-5(CAS DataBase Reference)
NIST Chemistry Reference3-Cyclobutene-1,2-dione, 3,4-dihydroxy-(2892-51-5)
EPA Substance Registry System3-Cyclobutene-1,2-dione, 3,4-dihydroxy- (2892-51-5)
Safety Information
Hazard Codes Xi
Risk Statements 36/37/38-43
Safety Statements 26-36-37/39
RIDADR 3261
WGK Germany 3
RTECS GU1800000
Hazard Note Irritant
TSCA Yes
HazardClass 8
PackingGroup II
HS Code 29144090
MSDS Information
ProviderLanguage
3,4-Dihydroxy-3-cyclobutene-1,2-dione English
SigmaAldrich English
ACROS English
ALFA English
Squaric acid Usage And Synthesis
Chemical PropertiesSquaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione), also known as quadratic acid, has the fascinating structure, and is a vinylogous carboxylic acid. The parent compound is a white,crystalline powder which melts at~300℃. It is highly acidic (pKa 1.5 for the first proton and 3.4 for the second) due to resonance stabilization of the anion and exhibits IR resonances indicative of strong hydrogen bonding [2326cm-1 (OH),1818 cm-1 (C=O), and 1639cm-1 (C=C)].The UV absorption spectrum suggests that the acid is essentially completely ionized. Squaric acid is freely soluble in water but has poor solubility in many organic solvents.Solutions give an intense purple color with iron(III) chloride, and are also known to decolorize bromine water, cerium(IV) nitrate, and permanganate solutions.As the carbonyl groups are similar to those of carboxylic acids rather than those of ketones, squaric acid does not react in the phenylhydrazine test.The squarate dianion is thought to be completely symmetrical (unlike squaric acid itself), with all C-C and C-O bond lengths being, respectively, identical, as the negative charges are equally distributed between allthe oxygen atoms.The IR spectrum of dipotassium squarate (dipotassium 3,4-dioxocy-clobut-1-ene-1,2-diolate) differs greatly from that of squaric acid, with the loss of the car-bonyl (C=O) and alkene(C=C) absorptions seen in the protonated form, and supportsthe proposed symmetrical structure.
UsesSquaric acid used as intermediate for squaraine dyes and heterocycles. Squaric acid is an immunotherapy used to treat common warts. This treatment is non-toxic, and easy to use. The treatment activated your immune system to combat the warts and therefore it may cause an allergic reaction , similar to poison oak. This reaction can be managed with a topical cortisone cream. Blistering and lightening of the skin may occur, but rarely.
Squaric acid derivatives – synthetic targets for ring expansion reactions
Uses3,4-Dihydroxy-3-cyclobutene-1,2-dione can be used:
  • In fluorescence detection in immunoassays, hybridization assays, enzymatic reactions, and other analytical procedures.
  • To form diffraction quality crystals.
  • To synthesize a squarate dianion, which is used as a building block to create uncharged polymeric networks. These ordered structures are used in catalysis, nonlinear optics, electrical conductivity, molecular recognition, and molecular sieves.
Uses3,4-Dihydroxy-3-cyclobutene-1,2-dione is used to produce diethoxy-cyclobutenedione by heating, pharmaceutical intermediates, squarylium dyes, and photoconducting squaraines; The dibutylester is used as a contact sensitizer in the treatment of alopecia and warts.
DefinitionChEBI: A carbon oxoacid that consists of 1,2-diketocyclobut-3-ene bearing two enolic hydroxy substituents at positions 3 and 4.
Synthesis Reference(s)Journal of the American Chemical Society, 88, p. 1533, 1966 DOI: 10.1021/ja00959a040
Tetrahedron Letters, 18, p. 4437, 1977
General Description3,4-dihydroxy-3-cyclobutene-1,2 dione, commonly known as squaric acid, is widely used in bioorganic and medicinal chemistry. It is an inhibitor of glyoxylase, semiqauric acid, pyruvate dehrogenase, and transketolase. It is used as a replacement for phosphate in a peptide-based ligand for an SH2 domain. Its derivatives are high-affinity ligands for excitatory amino acid receptors. These derivatives are also used as dyes for fluorescence detection of small biological molecules.
Biotechnological Applicationssquaric acid is widely used in bioorganic and medicinal chemistry. It is an inhibitor of glyoxylase, semiqauric acid, pyruvate dehrogenase, and transketolase. It is used as a replacement for phosphate in a peptide-based ligand for an SH2 domain. Its derivatives are high-affinity ligands for excitatory amino acid receptors. These derivatives are also used as dyes for fluorescence detection of small biological molecules.
squaric acid can be used:
In fluorescence detection in immunoassays, hybridization assays, enzymatic reactions, and other analytical procedures.
To form diffraction quality crystals.
To synthesize a squarate dianion, which is used as a building block to create uncharged polymeric networks. These ordered structures are used in catalysis, nonlinear optics, electrical conductivity, molecular recognition, and molecular sieves.
Purification MethodsPurify squaric acid by recrystallisation from H2O — this is quite simple because the acid is ~ 7% soluble in boiling H2O and only 2% at room temperature. It is not soluble in Me2CO or Et2O; hence it can be rinsed with these solvents and dried in air or a vacuum. It is not hygroscopic and gives an intense purple colour with FeCl3. It has IR max at 1820 (C=O) and 1640 (C=C) cm-1, and UV max at 269.5nm ( 37K M-1cm -1). [Cohn et al. J Am Chem Soc 81 3480 1959, Park et al. J Am Chem Soc 84 2919 1962] See also pKa values of 0.59 ±0.09 and 3.48 ±0.023 [Scwartz & Howard J Phys Chem 74 4374 1970]. [Schmidt & Reid Synthesis 869 1978, Beilstein 8 IV 2701.]
Tag:Squaric acid(2892-51-5) Related Product Information
Diethyl squarate Stearic acid Maleic acid Glycine Fumaric acid Folic acid Ethyl 2-(Chlorosulfonyl)acetate Fumaronitrile CIS-BUTENEDIOIC ANHYDRIDE 4'-Hydroxyacetophenone Fenofibric acid L(+)-Diethyl L-tartrate Perfluoro-2-methyl-2-pentene Methyl vinyl ketone 3,4-Dimethoxy-3-cyclobutene-1,2-dione 3,4-Diisopropoxy-3-cyclobutene-1,2-dione Dibutyl squarate 3,4-DIHYDROXY-3-CYCLOBUTENE-1,2-DIONE, DILITHIUM SALT, 98,3,4-DIHYDROXY-3-CYCLOBUTENE-1,2-DIONE, D ILITHIUM SALT, 98%