3,4-Dihydroxy-3-cyclobutene-1,2-dione TCI D1399

Chemical Identity

Other names: 1-Cyclobutene-3,4-dione-1,2-diol · Squaric Acid
CAS No.: 2892-51-5
PubChem: CID 17913·SID 87567905
Formula: C4H2O4
Molecular weight: 114.06 g/mol
Purity: >98.0%(HPLC)(T)
Reference databases: ChEBI·ChemSpider·ECHA·Wikipedia

Full identifiers (IUPAC, SMILES, InChIKey)

IUPAC: 3,4-dihydroxycyclobut-3-ene-1,2-dione
SMILES: C1(=C(C(=O)C1=O)O)O
InChIKey: PWEBUXCTKOWPCW-UHFFFAOYSA-N
MDL: MDL00001334

Rp 1.458.450,00

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3,4-Dihydroxy-3-cyclobutene-1,2-dione, better known as squaric acid, is a four-membered cyclic compound with two carbonyl groups and two hydroxyl groups in conjugation. Its unusual and highly symmetric structure makes it a valued building block in organic chemistry, materials chemistry, and medicinal chemistry. In the laboratory, squaric acid is used as a precursor to squaraine dyes, squarate esters, and squaramides. Each of these compound classes plays an important role in photonics, catalysis, and bioconjugation research, which makes this TCI reagent a useful starting material for a wide range of synthetic programmes.

Squaric acid is a fairly strong organic acid. The negative charge on its anion is spread evenly across the whole ring, so the anion is very stable and aromatic in character. Because of this, its derivatives tend to have flat, rigid geometries, which is useful when designing well-defined molecular architectures. Squaramides made from this acid are strong double hydrogen-bond donors, which is why they are widely used as organocatalysts and anion receptors. Condensing squaric acid with electron-rich aromatic compounds gives squaraine dyes with sharp absorption and emission in the red to near-infrared region. Together, these properties make the compound a popular choice for researchers who need a compact and versatile scaffold.

In Indonesia, squaric acid is relevant to organic chemistry research groups at universities and research institutes, especially those working on new synthetic methods, organocatalysis, and functional molecules. Materials science laboratories exploring dyes and optical materials can use it as an entry point to squaraine chemistry. Medicinal chemistry teams may use squarate esters and squaramides when building compound libraries or linking biomolecules. AMI Scientific supplies this TCI-brand building block to support these research activities.

TCI brochures (PDF)

Covalent Organic Framework (COF) Linkers 2026-05-18 · p. 6

Related TCI products

Squaraine dye synthesis: condensation with electron-rich aromatic compounds produces squaraine dyes with sharp red to near-infrared absorption and emission, supporting photonics and optical materials research.
Squaramide organocatalyst preparation: squaramides derived from this acid act as strong double hydrogen-bond donors, making them effective scaffolds for developing organocatalysts in asymmetric and method-development studies.
Anion receptor design: the rigid, flat squaramide motif and its strong hydrogen-bonding ability make squaric acid a logical starting point for building selective anion receptors in supramolecular chemistry.
Squarate ester preparation: squaric acid serves as a precursor to squarate esters, which are useful intermediates for further synthetic transformations and for building more elaborate four-membered-ring compounds.
Bioconjugation research: squaric acid derivatives play a recognised role in bioconjugation, giving medicinal chemistry and chemical biology groups a compact linker chemistry for joining molecules together.

Brand	TCI (product code D1399)
CAS number	2892-51-5
Molecular formula	—
Purity	—
Category	Chemistry > Building Blocks > Non-Heterocyclic Building Blocks
Pack sizes	available in the pack sizes listed on the product page
Physical form	solid; please check the supplier documentation for full details
Storage	keep tightly closed in a cool, dry place, following the TCI label and Safety Data Sheet

Store squaric acid in its original, tightly sealed container in a cool, dry, well-ventilated area away from moisture, heat sources, and incompatible materials such as strong bases and oxidising agents. If you transfer the material, use clean, dry, chemically compatible containers that are clearly labelled. Because this is a fairly strong organic acid, wear suitable gloves, safety glasses, and a lab coat, and avoid creating or breathing in dust. Weigh and handle it in a fume hood or a well-ventilated area. Always read the Safety Data Sheet before use and follow your institution's chemical hygiene and waste disposal procedures.

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