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Phenols

Squaric acid

Also known as Quadratic acid, 3,4-dihydroxycyclobut-3-ene-1,2-dione, Quadratsaeure

CAS 2892-51-5Formula C4H2O4Molar mass 114.06 g/molEC 220-761-4
GHS signal word: Warning. Pictograms: Harmful or irritant 42 suppliers listed
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Squaric acid chemical structure, C4H2O4, CAS 2892-51-5
2D chemical structure

Key facts

What buyers check first

All properties
CAS number
2892-51-5
Formula
C4H2O4
Molar mass
114.06 g/mol
EC number
220-761-4
HS code
290729
Category
Phenols

What is Squaric acid?

Plain description, key identifiers and synonyms

Squaric acid is a carbon oxoacid that consists of 1,2-diketocyclobut-3-ene bearing two enolic hydroxy substituents at positions 3 and 4. It has a role as a metabolite. It is a carbon oxoacid and an alicyclic ketone. It is a conjugate acid of a hydrogensquarate.

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
3,4-dihydroxycyclobut-3-ene-1,2-dione
CAS number
2892-51-5 CAS number cross-checkedOther or deprecated CAS: 31150-56-8
EC numbers
220-761-4, 693-144-4
Molecular formula
C4H2O4
UNII
SVR9D0VODW
MDL number
MFCD00001334
InChIKey
PWEBUXCTKOWPCW-UHFFFAOYSA-N
InChI
InChI=1S/C4H2O4/c5-1-2(6)4(8)3(1)7/h5-6H
SMILES (canonical and isomeric)
C1(=C(C(=O)C1=O)O)O

Synonyms

  • Quadratic acid
  • 3,4-dihydroxycyclobut-3-ene-1,2-dione
  • Quadratsaeure
  • 1,2-Diketo-3,4-dihydroxycyclobutene
  • Dihydroxycyclobutenedione
  • 3,4-Dihydroxy-3-cyclobutene-1,2-dione
  • 3-Cyclobutene-1,2-dione, 3,4-dihydroxy-
  • dihydroxycyclobut-3-ene-1,2-dione
  • Cyclobutenedione, dihydroxy-
  • 1,2-Dihydroxycyclobutene-3,4-dione
  • 1,2-Dihydroxycyclobutenedione
  • 3,4-Dihydroxy-cyclobutene-1,2-dione
  • Diketocyclobutenediol
  • Cyclobutene-1,2-dione, 3,4-dihydroxy-
  • 4-08-00-02701 (Beilstein Handbook Reference)
  • 1,2-dioxo-3,4-dihydroxycyclobutene
  • 1,2-Dihydroxy cyclobutenedione
  • 1,2-dioxo-3,4-dihydroxycyclobut-3-ene
  • 3,4-dihydroxy-cyclobut-3-ene-1,2-dione
  • 3,4-Dihydroxy-3-cyclobutene-1,2-dione-d2
  • 3,4-dihydroxy-3-cyclobutene-2-dione, QUADRATIC ACID
  • 3,4-Dihydroxy-3-cyclobutene-1,2-dione, Lonza quality, 98.50-101.00% (w/w) (HPLC)
  • 1,2-Dihydroxy-1-cyclobuten-3,4-dione
  • 3,2-dione
  • 3,4-Dihydroxy-3-cyclobuten-1,2-dion
Show all 34 synonyms
  • 1,4-dihydroxycyclobutene
  • Cyclobutene-1, 3,4-dihydroxy-
  • cyclobutenedione, 3,4-dihydroxy-
  • 3-Cyclobutene-1, 3,4-dihydroxy-
  • 1,2-Dihydroxy-3,4-cyclobutenedione
  • 1-Cyclobutene-3,4-dione-1,2-diol
  • 1,2-dihydroxy-l-cyclobutene-3,4-dione
  • 3,4-dihydroxy-3-cyclobuten-1,2-dione
  • 1,2-dihydroxy-1-cyclobutene-3,4-dione

Physical and chemical properties

Measured values and descriptors computed from the structure

Physical and chemical properties

Measured values, check the supplier specification for your grade

No measured properties are recorded for this substance yet. Ask suppliers for a technical data sheet.

Values vary by grade. Ask suppliers for the COA or TDS of the batch you buy.

Computed descriptors

Calculated from the structure, useful for screening and formulation

Molecular weight
114.06 g/molcalc.
Exact mass
113.9953 Dacalc.
LogP (octanol/water)
-1.31calc.
Topological polar surface area
74.6 Ųcalc.
Hydrogen bond donors
2calc.
Hydrogen bond acceptors
4calc.
Rotatable bonds
0calc.
Heavy atoms
8calc.
Rings
1calc.
Aromatic rings
1calc.
Fraction sp3 carbons
0calc.
Formal charge
0calc.
Stereocentres
0calc.
Lipinski rule of five
Passes (0 violations)calc.

Calculated for screening. Confirm critical figures with the supplier.

Murcko scaffold

The ring system that remains when every side chain is removed

Murcko scaffold of this chemical, O=c1ccc1=O

O=c1ccc1=O

1 ring, 6 atoms, the 3-Cyclobutene-1,2-dione ring system.

158 other chemicals share this scaffold

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Warning
GHS07: Harmful or irritant
Harmful or irritant

Hazard statements

  • H315Causes skin irritation.
  • H317May cause an allergic skin reaction.
  • H319Causes serious eye irritation.
  • H335May cause respiratory irritation.
Precautionary statements (18)
  • P261Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264Wash skin thoroughly after handling.
  • P264 + P265Wash skin thoroughly after handling. Do not touch eyes.
  • P271Use only outdoors or in a well-ventilated area.
  • P272Contaminated work clothing should not be allowed out of the workplace.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P302 + P352If on skin: Wash with plenty of water.
  • P304 + P340If inhaled: Remove person to fresh air and keep comfortable for breathing.
  • P305 + P351 + P338If in eyes: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P319Get medical help if you feel unwell.
  • P321Specific treatment (see supplemental first aid instructions on the label).
  • P332 + P317If skin irritation occurs: Get medical help.
  • P333 + P317If skin irritation or rash occurs: Get medical help.
  • P337 + P317If eye irritation persists: Get medical help.
  • P362 + P364Take off contaminated clothing. And wash it before reuse.
  • P403 + P233Store in a well-ventilated place. Keep container tightly closed.
  • P405Store locked up.
  • P501Dispose of contents and container in accordance with local regulations.

GHS classification summary, not a safety data sheet (SDS). Classifications can differ by supplier, grade and concentration. Always check the supplier's SDS.

Full safety data and first aid

Squaric acid suppliers

Sponsored listings first, then the documented ranking: membership, verification, replies, completeness, freshness and ratings

All 42 suppliers
30 of 30 offers

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Where suppliers are based

42 suppliers in 9 countries

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Squaric acid price

Indicative price range per kg from live supplier offers

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Uses and applications

What the substance is used for, by industry and function

Roles

  • metabolite

Regulatory status

Inventories, regulations and trade controls that list this substance

United States

  • TSCA inventory (USA)
    Status: Active in US commerce

HS code and trade data

Customs classification and reported world trade statistics

Global trade

World import and export statistics for the HS code Squaric acid is traded under.

HS 2907.29Indicative HS code

Polyphenols, phenol-alcohols, other

World exports in 2024
$535M
−27.0% vs 2023, imports $565M
2019 to 2024
Top exporters
  1. India * partner reported17.7%
  2. Germany16.5%
  3. Japan15.8%
Top importers
  1. United States13.1%
  2. Japan8.0%
  3. Belgium7.9%

* Partner reported figures, a lower bound.

Reported customs values in USD, not prices.Full trade data

The HS code shown for Squaric acid is indicative (it was assigned by structure rules). Confirm the classification with your customs broker before shipping.

Frequently asked questions

Quick answers about Squaric acid, based on the data on this page

What is Squaric acid?

Squaric acid is a carbon oxoacid that consists of 1,2-diketocyclobut-3-ene bearing two enolic hydroxy substituents at positions 3 and 4. It has a role as a metabolite. It is a carbon oxoacid and an alicyclic ketone. It is a conjugate acid of a hydrogensquarate.

What is the CAS number of Squaric acid?

The CAS registry number of Squaric acid is 2892-51-5. Other or deprecated CAS numbers: 31150-56-8.

What is the molecular formula and weight of Squaric acid?

The molecular formula of Squaric acid is C4H2O4 and its molar mass is 114.06 g/mol.

What is Squaric acid used for?

Known uses and roles of Squaric acid include building blocks in research and laboratory, screening compounds in research and laboratory and metabolite.

Is Squaric acid hazardous?

Squaric acid carries the GHS signal word "Warning". Main hazards: causes skin irritation, may cause an allergic skin reaction, causes serious eye irritation. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Squaric acid?

Squaric acid is usually classified under HS code 290729 (Polyphenols, phenol-alcohols, other). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Squaric acid?

CompoundList lists 42 suppliers of Squaric acid in China, United States, Canada, Germany and 5 more. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Squaric acid in India?

1 supplier in India list Squaric acid on CompoundList. Filter the suppliers list by country and send a request to compare prices, grades and delivery times.

What is the price of Squaric acid?

Suppliers quote Squaric acid on request because prices depend on grade, purity, quantity and destination. A free request on CompoundList gets you several quotes to compare.

Guides for buyers

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Data last updated 7 Oct 2026. Details may have changed, please confirm them with the supplier. Report an error on this page
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