H

Hydroquinone

IUPAC: benzene-1,4-diol

C6H6O2 Organic Compounds CAS 123-31-9
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Quick Reference
Formula / NotationC6H6O2
CAS Number123-31-9
Molecular Weight110.11
Melting Point338 to 340 °F (EPA, 1998)
Boiling Point545 to 549 °F at 760 mmHg (EPA, 1998)
Density1.332 at 59 °F (EPA, 1998) - Denser than water; will sink
Solubility10 to 50 mg/mL at 68 °F (NTP, 1992)
AppearanceHydroquinone appears as light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption.
Also Known Asbenzene-1,4-diol; 123-31-9; Benzene-1,4-diol; 1,4-benzenediol; Quinol; 1,4-Dihydroxybenzene; p-Hydroquinone; p-Hydroxyphenol; p-Benzenediol; p-Dihydroxybenzene
CategoryOrganic Compounds

What is Hydroquinone?

Hydroquinone is a benzenediol comprising benzene core carrying two hydroxy substituents para to each other. It has a role as an antioxidant, a cofactor, a carcinogenic agent, a mouse metabolite, a human xenobiotic metabolite, an Escherichia coli metabolite and a skin lightening agent. It is a benzenediol and a member of hydroquinones.

Formula & Notation

C6H6O2

IUPAC Name: benzene-1,4-diol

Other Names / Synonyms: benzene-1,4-diol; 123-31-9; Benzene-1,4-diol; 1,4-benzenediol; Quinol; 1,4-Dihydroxybenzene; p-Hydroquinone; p-Hydroxyphenol; p-Benzenediol; p-Dihydroxybenzene

Properties & Characteristics

Appearance: Hydroquinone appears as light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption.. Molecular formula: C6H6O2. Molecular weight: 110.11 g/mol. Boiling point: 545 to 549 °F at 760 mmHg (EPA, 1998). Melting point: 338 to 340 °F (EPA, 1998). Density: 1.332 at 59 °F (EPA, 1998) - Denser than water; will sink. Solubility: 10 to 50 mg/mL at 68 °F (NTP, 1992). Vapor pressure: 4 mmHg at 302 °F (EPA, 1998). LogP: 0.6.

Physical Data

PropertyValue
Melting Point338 to 340 °F (EPA, 1998)
Boiling Point545 to 549 °F at 760 mmHg (EPA, 1998)
Density1.332 at 59 °F (EPA, 1998) - Denser than water; will sink
Molecular Weight110.11
Solubility10 to 50 mg/mL at 68 °F (NTP, 1992)
AppearanceHydroquinone appears as light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption.

Uses & Applications

Used as an industrial feedstock, solvent, pharmaceutical intermediate, flavoring agent, or chemical building block.

Safety Information

Flammable or irritant. Many organic compounds are flammable liquids or vapours. Keep away from ignition sources. Consult SDS for specific hazard data.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Hydroquinone
Formula C6H6O2
CAS Number 123-31-9
Molecular Weight 110.11
Synonyms benzene-1,4-diol; 123-31-9; Benzene-1,4-diol; 1,4-benzenediol; Quinol; 1,4-Dihydroxybenzene; p-Hydroquinone; p-Hydroxyphenol; p-Benzenediol; p-Dihydroxybenzene

Frequently Asked Questions

Hydroquinone is a benzenediol comprising benzene core carrying two hydroxy substituents para to each other. It has a role as an antioxidant, a cofactor, a carcinogenic agent, a mouse metabolite, a human xenobiotic metabolite, an Escherichia coli metabolite and a skin lightening agent. It is a benzenediol and a member of hydroquinones.

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Editorial standards: Chemical data is sourced from peer-reviewed literature, CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA, and IAEA. For educational purposes only — always consult official SDS documentation and qualified professionals before handling chemicals.