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Hydroquinone structure
Chemical Name:
HQ;he5;HE 5;Artra;diak5;QUINOL;Diak 5;Melanex;tenoxhq;Phiaquin
Molecular Formula:
Formula Weight:
MOL File:

Hydroquinone Properties

Melting point:
172-175 °C(lit.)
Boiling point:
285 °C(lit.)
vapor density 
3.81 (vs air)
vapor pressure 
1 mm Hg ( 132 °C)
refractive index 
Flash point:
165 °C
storage temp. 
H2O: 50 mg/mL, clear
Needle-Like Crystals or Crystalline Powder
10.35(at 20℃)
White to off-white
Water Solubility 
70 g/L (20 ºC)
Air & Light Sensitive
Henry's Law Constant
(x 10-9 atm?m3/mol): <2.07 at 20 °C (approximate - calculated from water solubility and vapor pressure)
Exposure limits
NIOSH REL: 15-min ceiling 2, IDLH 50; OSHA PEL: TWA 2; ACGIH TLV: TWA 2 (adopted).
Stable. Combustible. Incompatible with strong oxidizing agents, strong bases, oxygen, ferric salts. Light and air-sensitive. Discolours in air.
Indirect Additives used in Food Contact Substances
CAS DataBase Reference
123-31-9(CAS DataBase Reference)
EWG's Food Scores
3 (Vol. 15, Sup 7, 71) 1999
NIST Chemistry Reference
EPA Substance Registry System
Hydroquinone (123-31-9)
  • Risk and Safety Statements
Signal word  Danger
Hazard statements  H302-H317-H318-H341-H351-H410-H400
Precautionary statements  P273-P280-P305+P351+P338-P501-P201-P305+P351+P338+P310-P308+P313-P301+P312+P330
Hazard Codes  Xn,N
Risk Statements  22-40-41-43-50-68-R68-R50-R43-R41-R40-R22
Safety Statements  26-36/37/39-61-S61-S36/37/39-S26
RIDADR  2662
WGK Germany  3
RTECS  MX3500000
Autoignition Temperature 930 °F
HazardClass  9
PackingGroup  III
HS Code  29072210
Toxicity LD50 orally in rats: 320 mg/kg (Woodard)
NFPA 704
2 0

Hydroquinone price More Price(20)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
Sigma-Aldrich 74347 Hydroquinone certified reference material, TraceCERT 123-31-9 100mg $101 2020-08-18 Buy
Sigma-Aldrich 1324002 Hydroquinone United States Pharmacopeia (USP) Reference Standard 123-31-9 500mg $366 2020-08-18 Buy
TCI Chemical H0186 Hydroquinone >99.0%(T) 123-31-9 25g $16 2020-06-24 Buy
TCI Chemical H0186 Hydroquinone >99.0%(T) 123-31-9 500g $33 2020-06-24 Buy
Alfa Aesar A11411 Hydroquinone, 99% 123-31-9 250g $22.4 2020-06-24 Buy

Hydroquinone Chemical Properties,Uses,Production

Chemical Properties

white needle-like crystals or crystalline powder

Chemical Properties

Hydroquinone, a colorless, hexagonal prism, has been reported to be a good antimitotic and tumor-inhibiting agent. It is a reducing agent used in a photographic developer, which polymerizes in the presence of oxidizing agents. In the manufacturing industry it may occur include bacteriostatic agent, drug, fur processing, motor fuel, paint, organic chemicals, plastics, stone coating, and styrene monomers.

Physical properties

Colorless to pale brown, odorless, hexagonal crystals




Use as photographic reducer and developer; as reagent in the determination of small quantities of phosphate; as antioxidant. Depigmentor


hydroquinone is a pigment-lightening agent used in bleaching creams. Hydroquinone combines with oxygen very rapidly and becomes brown when exposed to air. Although it occurs naturally, the synthetic version is the one commonly used in cosmetics. Application to the skin may cause allergic reaction and increase skin sun sensitivity. Hydroquinone is potentially carcinogenic and is associated with causing ochronosis, a discoloration of the skin. The u.S. FDA has banned hydroquinone from oTC cosmetic formulations, but allows 4 percent in prescription products. Its use in cosmetics is prohibited in some european countries and in Australia.


K channel agonist, antihypertensive


reducing agent prevents polymerization of resin monomers lightens darkened skin, light sensitive


Photographic reducer and developer; antioxidant; stabilizing agent for some polymers; intermediate in the manufacturing of some dyes and pigments; in cosmetic formulations.


ChEBI: A benzenediol comprising benzene core carrying two hydroxy substituents para to each other.


Hydroquinone interferes with the production of the pigment melanin by epidermal melanocytes through at least two mechanisms: it competitively inhibits tyrosinase, one of the principal enzymes responsible for converting tyrosine to melanin, and it selectively damages melanocytes and melanosomes (the organelles within which melanin is stored).

Production Methods

There are three current manufacturing processes for HQ: oxidative cleavage of diisopropylbenzene, oxidation of aniline, and hydroxylation of phenol.
Diisopropylbenzene is air oxidized to the intermediate diisopropylbenzene bishydroperoxide. This hydroperoxide is purified by extraction and reacted further to form hydroquinone. The purified product is isolated by filtration and packaged. The process can be almost entirely closed, continuous, computer-controlled, and monitored.
HQcan also be prepared by oxidizing aniline to quinone in the presence of manganese dioxide and sulfuric acid. p-Benzoquinone is then reduced to HQ using iron oxide. The resulting hydroquinone is crystallized and dried. The process occurs in a closed system.
HQis also manufactured by hydroxylation of phenol using hydrogen peroxide as a hydroxylation agent. The reaction is catalyzed by strong mineral acids or ferrous or cobalt salts.

Manufacturing Process

Into a pressure reactor there was charged 100 ml of methanol and 1 g of diruthenium nonacarbonyl. The reactor was closed, cooled in solid carbon dioxide/acetone, and evacuated. Acetylene, to the extent of 1 mol (26 g), was metered into the cold reactor. Carbon monoxide was then pressured into this vessel at 835-980 atmospheres, during a period of 16.5 hours; while the reactor was maintained at 100°C to 150°C. The reactor was then cooled to room temperature and opened.
The reaction mixture was removed from the vessel and distilled at a pressure of 30-60 mm, and a bath temperature of 30°C to 50°C until the methanol had all been removed. The extremely viscous tarry residue remaining in the still pot was given a very crude distillation, the distillate boiling at 82°C to 132°C/2 mm. In an attempt to purify this distillate by a more careful distillation, 5.3 g of a liquid distilling from 53°C to 150°C/5 mm was collected. At this point, much solid sublimate was noted not only in this distillate but in the condenser of the still. 7 g of the solid sublimate was scraped out of the condenser of the still. Recrystallization of the sublimate from ethyl acetate containing a small amount of petroleum ether gave beautiful crystals melting at 175°C to 177°C (5 g). Infrared analysis confirmed that this compound was hydroquinone (9% conversion).

brand name

Aida;Ambi- skin tone;Black and white;Creme des 3 fleur d'orient;Eldopaque forte;Eldoquin forte 4% cream;Epocler;Esoterica facial;Esoterica regular;Esoterica sensitive skin;Esoterica sunscreen;Melanex topical sollution;Melpaque hp;Melqui hp;Neostrata aha gel;Neostrata hq;Nuquin hp;Pigmanorm;Porcelana;Sinquin;Solaquin forte sun bleaching;Superfade age spot;Ultraquin plaine.

Therapeutic Function


World Health Organization (WHO)

Hydroquinone was introduced in 1965 as a topical depigmenting agent for hyperpigmentation. At high concentrations hydroquinone is corrosive and in most countries has been restricted to the level of approximately 2% and limited to the period of less than 2 months. Additional consideration for restrictive action is that animal experiments have also demonstrated carcinogenic and mutagenic potential of hydroquinone.

Synthesis Reference(s)

Chemistry Letters, 14, p. 731, 1985
The Journal of Organic Chemistry, 50, p. 1722, 1985
Tetrahedron Letters, 22, p. 2337, 1981 DOI: 10.1016/S0040-4039(01)82900-2

General Description

Light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption.

Air & Water Reactions

Darkens on exposure to air and light. Miscible in water. Solutions become brown in air due to oxidation. Oxidation is very rapid in the presence of alkali.

Reactivity Profile

Hydroquinone is a slight explosion hazard when exposed to heat. Incompatible with strong oxidizing agents. Also incompatible with bases. Hydroquinone reacts with oxygen and sodium hydroxide. Reacts with ferric salts . Hot and/or concentrated NaOH can cause Hydroquinone to decompose exothermically at elevated temperature. (NFPA Pub. 491M, 1975, 385)


Toxic by ingestion and inhalation, irritant. Questionable carcinogen.

Health Hazard

Exposures to hydroquinone in large quantities by accidental oral ingestion produce toxicity and poisoning. The symptoms of poisoning include, but are not limited to, blurred speech, tinnitus, tremors, sense of suffocation, vomiting, muscular twitching, headache, convul- sions, dyspnea and cyanosis from methemoglobinemia, coma, and collapse from respira- tory failure. Occupational workers should be allowed to work with protective clothing and dust masks with full-face or goggles to protect the eyes, and under proper management.

Health Hazard

Hydroquinone is very toxic; the probable oral lethal dose for humans is 50-500 mg/kg, or between 1 teaspoon and 1 ounce for a 150 lb. person. It is irritating but not corrosive. Fatal human doses have ranged from 5-12 grams, but 300-500 mg have been ingested daily for 3-5 months without ill effects. Death is apparently initiated by respiratory failure or anoxia.

Fire Hazard

Dust cloud may explode if ignited in an enclosed area. Hydroquinone can react with oxidizing materials and is rapidly oxidized in the presence of alkaline materials. Oxidizes in air.

Contact allergens

Hydroquinone is used in photography developers (black and white, X-ray, and microfilms), in plastics, in hair dyes as an antioxidant and hair colorant. Hydroquinone is found in many skin bleaching creams.

Clinical Use

Hydroquinone is applied topically to treat disorders characterized by excessive melanin in the epidermis, such as melasma. In the United States, nonprescription skin-lightening products contain hydroquinone at concentrations of 2% or less; higher concentrations are available by prescription.

Side effects

The incidence of adverse effects with hydroquinone increases in proportion to its concentration. A relatively common side effect is local irritation, which may actually exacerbate the discoloration of the skin being treated. Allergic contact dermatitis occurs less commonly. A rare but more serious complication is exogenous ochronosis, in which a yellow-brown pigment deposited in the dermis results in blue-black pigmentation of the skin that may be permanent.


No case reports of cancer associated with HQ exposure have been published.


Hydroquinone occurs naturally in strawberry tree leaves, pears, blackberries, Chinese alpenrose, bilberries, blackberries, hyacinth flowers, anise, cowberries, and lingonberries (Duke, 1992).

Environmental Fate

Biological. In activated sludge, 7.5% mineralized to carbon dioxide after 5 d (Freitag et al., 1985). Under methanogenic conditions, inocula from a municipal sewage treatment plant digester degraded hydroquinone to phenol prior to being mineralized to carbon dioxide and methane (Young and Rivera, 1985). In various pure cultures, hydroquinone degraded to the following intermediates: benzoquinone, 2-hydroxy-1,4-benzoquinone, and β-ketoadipic acid. Hydroquinone also degraded in activated sludge but no products were identified (Harbison and Belly, 1982). Heukelekian and Rand (1955) reported a 5-d BOD value of 0.74 g/g which is 39.2% of the ThOD value of 1.89 g/g. In activated sludge inoculum, following a 20-d adaptation period, 90.0% COD removal was achieved. The average rate of biodegradation was 54.2 mg COD/g?h (Pitter, 1976).
Photolytic. A carbon dioxide yield of 53.7% was achieved when hydroquinone adsorbed on silica gel was irradiated with light (λ >290 nm) for 17 h (Freitag et al., 1985). Chemical/Physical. Ozonolysis products reported are p-quinone and dibasic acids (Verschueren, 1983). Moussavi (1979) studied the autoxidation of hydroquinone in slightly alkaline (pH 7 to 9) aqueous solutions at room temperature. The oxidation of hydroquinone by oxygen followed first-order kinetics that yielded hydrogen peroxide and p-quinone as products. At pH values of 7.0, 8.0, and 9.0, the calculated half-lives of this reaction were 111, 41, and 0.84 h, respectively (Moussavi, 1979).
Chlorine dioxide reacted with hydroquinone in an aqueous solution forming p-benzoquinone (Wajon et al., 1982). Kanno et al. (1982) studied the aqueous reaction of hydroquinone and other substituted aromatic hydrocarbons (aniline, toluidine, 1- and 2-naphthylamine, phenol, cresol, pyrocatechol, resorcinol, and 1-naphthol) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. As the pH was lowered, the amount of cyanogen chloride formed increased (Kanno et al., 1982).
At influent concentrations of 1.0, 0.1, 0.01, and 0.001 mg/L, the GAC adsorption capacities were 160, 90, 51, and 29 mg/g, respectively (Dobbs and Cohen, 1980).

Purification Methods

Crystallise quinol from acetone, *benzene, EtOH, EtOH/*benzene, water or acetonitrile (25g in 30mL), preferably under nitrogen. Dry it under vacuum. [Wolfenden et al. J Am Chem Soc 109 463 1987, Beilstein 6 H 836, 6 IV 5712.]

Hydroquinone Preparation Products And Raw materials

Raw materials

Preparation Products

Hydroquinone Suppliers

Global( 516)Suppliers
Supplier Tel Fax Email Country ProdList Advantage
Hebei Yanxi Chemical Co., Ltd.
86-311-66561638 CHINA 519 58
Hefei TNJ Chemical Industry Co.,Ltd.
86-0551-65418684 18949823763
86-0551-65418684 China 2754 55
Hangzhou FandaChem Co.,Ltd.
0086 158 5814 5714 (Mobile
+86-571-56059825 CHINA 3275 55
Yancheng Green Chemicals Co.,Ltd
86-515-87883652 CHINA 71 58
Henan Xiangtong Chemical Co., Ltd.
86-371-86017988 CHINA 275 58
Henan Tianfu Chemical Co.,Ltd.
0371-55170693 CHINA 22624 55
Tianjin Zhongxin Chemtech Co., Ltd.
022-66880086 CHINA 602 58
Hebei Chishuo Biotechnology Co., Ltd.
13292891350 +86 311 66567340 CHINA 1005 58
career henan chemical co
+86-371-86658258 CHINA 30039 58
Hebei Ruishun Trade Co.,LTD
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View Lastest Price from Hydroquinone manufacturers

Image Release date Product Price Min. Order Purity Supply Ability Manufacturer
2020-08-17 Hydroquinone
US $50.00-30.00 / 公斤 1公斤 99.8% 10tons Hebei Runbin Biotechnology Co. LTD
2020-07-13 Dimefluthrin
US $110.00 / Kg/Drum 25KG 95% 1000tons/month Hebei Yanxi Chemical Co., Ltd.
2020-07-13 Hydroquinone
US $10.00 / Kg/Bag 25KG 99.8% 1000tons/month Hebei Yanxi Chemical Co., Ltd.

Hydroquinone Spectrum

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