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HONGKUN / PRODUCT DIRECTORY

Squaric acid | CAS 2892-51-5

A four-membered oxocarbon precursor for squaraine and squarylium chromophores, with free-acid identity and impurity control important when building optical molecules.

CAS2892-51-5
Molecular formulaC4H2O4
Molecular weight114.06 g/mol

Product overview

Squaric acid concentrates two hydroxy and two carbonyl groups around a four-carbon ring. This small scaffold appears in dye construction and in squarate coordination chemistry. It should be distinguished from dialkyl squarates and squarate salts, which have different reactive forms. Buyers developing optical materials should define the free-acid assay and the organic or inorganic contaminants that matter to the planned synthesis.

Chemical identity

Chemical name
Squaric acid
CAS number
2892-51-5
Molecular formula
C4H2O4
Molecular weight
114.06 g/mol

Application context

Squaric acid is used to prepare squaraine and squarylium dyes. A published example couples it with a trimethylindolenine building block to obtain a dye investigated for chromogenic anion sensing. Its role is to supply the central oxocarbon scaffold; the attached aromatic or heteroaromatic groups determine the resulting chromophore. Squarate species also appear in coordination-network research. Optical performance and sensing behavior belong to the derivative or assembled system, so material qualification should follow the intended chemistry.

Chemistry and synthetic role

The conjugated oxygen-rich ring can be converted into substituted chromophore structures or deprotonated squarate species, depending on the application.

Quality review

Acid, ester or salt

Specify the free acid explicitly and confirm structural identity.

Organic purity

Agree a suitable assay and related-substance profile for the target dye synthesis.

Inorganic contribution

For optical or coordination work, define relevant metal or ash criteria and the water basis of the assay.

Preparing a specification

Request free squaric acid with a defined assay basis, organic-related-substance criteria and any metal, ash or water controls needed for the intended chromophore.

Packaging and storage

Confirm container compatibility, closure and net weight for the selected grade and destination. Follow the actual supplier SDS and batch label for storage and transport.

Documentation

Request the batch COA, SDS and analytical methods covering the agreed purchasing specification. Confirm which supporting chromatograms and application-specific records are available from the selected manufacturer.

Procurement questions

Is squaric acid itself the final squaraine dye?

No. It provides the central scaffold used to construct the substituted chromophore.

Can diethyl squarate be ordered under the same CAS?

No. The ester is a distinct chemical form with its own identity.

Should metal content be specified?

Include selected metals when they could affect optical measurements or coordination chemistry.

Technical sources
  1. PubChem CAS identity lookupNCBI / PubChem
  2. Squaric acidSigma-Aldrich
  3. Squarylium-based chromogenic anion sensorsPrimary research indexed by PubMed

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