Chinese Japanese Germany Korea

Squaric acid

Squaric acid
Squaric acid structure
Chemical Name:
Squaric acid
Squaric;2-dione;NSC 624671;squaricaci;SQUARC ACID;SQUARIC ACID;QUADRATIC ACID;obutene-1,2-dione;TIMTEC-BB SBB007891;3,4-Dihydroxy-3-cycL
Molecular Formula:
Formula Weight:
MOL File:

Squaric acid Properties

Melting point:
>300 °C(lit.)
Boiling point:
1.82 g/cm3
refractive index 
1.5800 (estimate)
Flash point:
190 °C
storage temp. 
Inert atmosphere,Room Temperature
1.5??(at 25℃)
Crystalline Powder
White to beige
1 (1g/l, H2O, 20℃)
Water Solubility 
20 g/L (30 ºC)
CAS DataBase Reference
2892-51-5(CAS DataBase Reference)
EWG's Food Scores
NIST Chemistry Reference
3-Cyclobutene-1,2-dione, 3,4-dihydroxy-(2892-51-5)
EPA Substance Registry System
3-Cyclobutene-1,2-dione, 3,4-dihydroxy- (2892-51-5)
  • Risk and Safety Statements
Signal word  Warning
Hazard statements  H315-H317-H319-H335
Precautionary statements  P264-P302+P352+P332+P313+P362+P364-P305+P351+P338+P337+P313-P280a-P304+P340-P405-P501a-P261-P280-P305+P351+P338
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
HazardClass  8
PackingGroup  II
HS Code  29144090

Squaric acid price More Price(12)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
Sigma-Aldrich 123447 3,4-Dihydroxy-3-cyclobutene-1,2-dione 99% 2892-51-5 5g $52.8 2021-03-22 Buy
Sigma-Aldrich 123447 3,4-Dihydroxy-3-cyclobutene-1,2-dione 99% 2892-51-5 25g $163 2021-03-22 Buy
TCI Chemical D1399 3,4-Dihydroxy-3-cyclobutene-1,2-dione >98.0%(HPLC)(T) 2892-51-5 5g $57 2021-03-22 Buy
TCI Chemical D1399 3,4-Dihydroxy-3-cyclobutene-1,2-dione >98.0%(HPLC)(T) 2892-51-5 25g $170 2021-03-22 Buy
Alfa Aesar A15169 3,4-Dihydroxy-3-cyclobutene-1,2-dione, 98+% 2892-51-5 1g $21.5 2021-03-22 Buy

Squaric acid Chemical Properties,Uses,Production

Chemical Properties

Squaric 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.


Squaric 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


ChEBI: 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

Biotechnological Applications

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.
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 Methods

Purify 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.]

Squaric acid Preparation Products And Raw materials

Raw materials

Preparation Products

Squaric acid Suppliers

Global( 322)Suppliers
Supplier Tel Fax Email Country ProdList Advantage
+86-571-8723 8903
+86-571-87063838 CHINA 997 58
Springchem New Material Technology Co.,Limited
+8613917661608 +86-021-62885108 China 2065 57
Capot Chemical Co.,Ltd.
+86(0)13336195806 +86-571-85586718
+86-571-85864795 China 20010 60
Shanghai Time Chemicals CO., Ltd.
+8618017249410 +86-021-57951555
+86-021-57951555 CHINA 1365 55
Hangzhou FandaChem Co.,Ltd.
+86-571-56059825 CHINA 8882 55
+86 21 5161 9050/ 5187 7795
+86 21 5161 9052/ 5187 7796 CHINA 26734 60
career henan chemical co
+86-371-86658258 CHINA 29959 58
Shandong chuangyingchemical Co., Ltd.
18853181302 CHINA 5917 58
Chongqing Chemdad Co., Ltd
+86-13650506873 CHINA 37282 58
Alchem Pharmtech,Inc.
8485655694 United States 63726 58

View Lastest Price from Squaric acid manufacturers

Image Release date Product Price Min. Order Purity Supply Ability Manufacturer
2021-10-11 Squaric Acid
US $10.00 / KG 1KG 99% 20 tons Hebei Zhanyao Biotechnology Co. Ltd
2020-12-02 3,4-Dihydroxy-3-cyclobutene-1,2-dione
US $10.00 / KG 1KG 99.99 10Ton Hebei Miaobian Biotechnology Co., Ltd
2019-07-06 3,4-Dihydroxy-3-cyclobutene-1,2-dione
US $7.00 / kg 1kg 99% 100kg career henan chemical co

Squaric acid Spectrum

2892-51-5(Squaric acid)Related Search:

Copyright 2017 © ChemicalBook. All rights reserved