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Impurities and reference standards

Phthalic acid

Also known as 1,2-benzenedicarboxylic acid, o-phthalic acid, benzene-1,2-dicarboxylic acid

CAS 88-99-3Formula C8H6O4Molar mass 166.13 g/molEC 201-873-2
GHS signal word: Danger. Pictograms: Serious health hazard 113 suppliers listed
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Phthalic acid chemical structure, C8H6O4, CAS 88-99-3
2D chemical structure

Key facts

What buyers check first

All properties
Appearance
Colorless crystals
Melting point
230 °C
Boiling point
598.00 K (Based on predicted value for phthalic acid by Meissner's method with a suitabl…
Density
1.593 g/cm³ at 15 °C
Flash point
168 °C
HS code
291739
Category
Impurities and reference standards
Illustrative photo, colourless crystals beside a jumbo bulk bag in a chemical plant
Typical packagingIllustrative packaging image, not the actual product

What is Phthalic acid?

Plain description, key identifiers and synonyms

Phthalic acid is a benzenedicarboxylic acid cosisting of two carboxy groups at ortho positions. It has a role as a human xenobiotic metabolite. It is a conjugate acid of a phthalate(1-).

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
phthalic acid
CAS number
88-99-3 CAS number cross-checkedOther or deprecated CAS: 254110-94-6
EC number
201-873-2
Molecular formula
C8H6O4
UNII
6O7F7IX66E
MDL number
MFCD00002467
InChIKey
XNGIFLGASWRNHJ-UHFFFAOYSA-N
InChI
InChI=1S/C8H6O4/c9-7(10)5-3-1-2-4-6(5)8(11)12/h1-4H,(H,9,10)(H,11,12)
SMILES (canonical and isomeric)
C1=CC=C(C(=C1)C(=O)O)C(=O)O

Synonyms

  • 1,2-benzenedicarboxylic acid
  • o-phthalic acid
  • benzene-1,2-dicarboxylic acid
  • o-dicarboxybenzene
  • o-benzenedicarboxylic acid
  • Acide phtalique
  • Kyselina ftalova
  • ortho-phthalic acid
  • hydron, phthalate
  • Pathalic acid
  • Orthophthalic acid
  • Sunftal 20
  • PhthalicAcid-13C2
  • Copper(ii)phthalate
  • Fluorescein EP Impurity B
  • Leadphthalate,dibasic
  • Phthalic-13C Acid
  • Phthalicacid
  • Phthalic Acid-13C2
  • Phthalate standard for IC
  • Alizarinate
  • Naphthalinate
  • Phthalinate
  • Alizarinic acid
  • Phthalinic acid
Show all 36 synonyms
  • Naphthalinic acid
  • o-Carboxybenzoate
  • 4kww
  • folpet TP2
  • phthals&#xe4, ure
  • Phthalic acid CRS
  • Benzene-1,2-dicarboxylic Acid, Phthalic acid, Fluorescein Sodium Imp. B (EP), Fluorescein Imp. B (EP), Fluorescein Sodium Impurity B, Fluorescein Impurity B
  • o-Carboxybenzoic acid
  • o-Benzenedicarboxylate
  • 1,2-dicarboxybenzene
  • Phthalic acid, ~99%

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

Appearance
Colorless crystalsexp.
Melting point
230 °Cexp.
Boiling point
598.00 K (Based on predicted value for phthalic acid by Meissner's method with a suitable adjustment for isomerism based on similar compound relationships.)exp.
Density
1.593 g/cm³ at 15 °Cexp.
Flash point
168 °Cexp.
Solubility
1 g dissolves in 160 ml water, 10 ml alc, 205 ml ether, 5.3 ml methanol, practically insol in chloroformexp.
Vapour pressure
6.36 × 10⁻⁷ mm Hg at 25 °Cexp.

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
166.13 g/molcalc.
Exact mass
166.0266 Dacalc.
LogP (octanol/water)
1.08calc.
Topological polar surface area
74.6 Ųcalc.
Hydrogen bond donors
2calc.
Hydrogen bond acceptors
2calc.
Rotatable bonds
2calc.
Heavy atoms
12calc.
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, c1ccccc1

c1ccccc1

1 ring, 6 atoms, the Benzene ring system.

485,677 other chemicals share this scaffold

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Danger
GHS08: Serious health hazard
Serious health hazard
110NFPA 704 rating

Hazard statements

  • H360DMay damage the unborn child.
Precautionary statements (5)
  • P203Obtain, read and follow all safety instructions before use.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P318If exposed or concerned, get medical advice.
  • 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

Phthalic acid suppliers

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

All 113 suppliers
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Where suppliers are based

113 suppliers in 21 countries

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Phthalic acid price

Indicative price range per kg from live supplier offers

No published prices right now

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Uses and applications

What the substance is used for, by industry and function

Medicine ... Organic synthesis. Analytical reagent.

Dyes, phenolphthalein, phthalimide, anthranilic acid, synthetic perfumes, laboratory reagent.

Use classes: Metabolites, Transformation products, Pesticide transformation products.

Roles

  • animal metabolite
  • eukaryotic metabolite
  • human metabolite
  • human xenobiotic metabolite
  • mammalian metabolite
  • metabolite
  • xenobiotic metabolite

Functional uses

  • Flavouring and nutrient
  • Lubricating agent
  • Plasticizer

How it is made

Vapor-phase oxidation of naphthalene, catalyzed by vanadium and molybdenum oxides, followed by hydrolysis

Manufactured by catalytic oxidation of o-toluic acid and oxidation of xylene: Taylor, Dean, US 3064046 (1962 to I.C.I.), Cier, US 3088974 (1963 to Esso Res. & Eng.). Isolation from the fungus, Gibbererella fujikuroi.

Regulatory status

Inventories, regulations and trade controls that list this substance

Europe

  • EU harmonised classification (CLP Annex VI)
    Index no: 607-483-00-2

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 Phthalic acid is traded under.

HS 2917.39Indicative HS code

Aromatic polycarboxylic acids, not elsewhere classified in subheading 2917.3

World exports in 2024
$1.87B
+19.8% vs 2023, imports $2.65B
2019 to 2024
Top exporters
  1. China31.7%
  2. South Korea12.9%
  3. United States9.8%
Top importers
  1. Egypt12.7%
  2. United States12.5%
  3. China10.3%
Reported customs values in USD, not prices.Full trade data

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

Frequently asked questions

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

What is Phthalic acid?

Phthalic acid is a benzenedicarboxylic acid cosisting of two carboxy groups at ortho positions. It has a role as a human xenobiotic metabolite. It is a conjugate acid of a phthalate(1-).

What is the CAS number of Phthalic acid?

The CAS registry number of Phthalic acid is 88-99-3. Other or deprecated CAS numbers: 254110-94-6.

What is the molecular formula and weight of Phthalic acid?

The molecular formula of Phthalic acid is C8H6O4 and its molar mass is 166.13 g/mol.

What is Phthalic acid used for?

Medicine ... Organic synthesis. Analytical reagent. Dyes, phenolphthalein, phthalimide, anthranilic acid, synthetic perfumes, laboratory reagent. Use classes: Metabolites, Transformation products, Pesticide transformation products.

Is Phthalic acid hazardous?

Phthalic acid carries the GHS signal word "Danger". Main hazards: may damage the unborn child. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Phthalic acid?

Phthalic acid is usually classified under HS code 291739 (Aromatic polycarboxylic acids, their anhydrides, halides, peroxides, peroxyacids and…). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Phthalic acid?

CompoundList lists 113 suppliers of Phthalic acid in China, United States, United Kingdom, Germany and 17 more. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Phthalic acid in India?

4 suppliers in India list Phthalic 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 Phthalic acid?

Suppliers quote Phthalic 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

Practical guides that help when you source, ship or handle Phthalic acid

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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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