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.
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.
Light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption.
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,
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
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).
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.
Use as photographic reducer and developer; as reagent in the determination of small quantities of phosphate; as antioxidant. Depigmentor
Photographic reducer and developer; antioxidant; stabilizing agent for some polymers; intermediate in the manufacturing of some dyes and pigments; in cosmetic formulations.
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.
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)
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.
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.
Hydroquinone occurs naturally in strawberry tree leaves, pears, blackberries, Chinese
alpenrose, bilberries, blackberries, hyacinth flowers, anise, cowberries, and lingonberries (Duke,
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.
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.
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).
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.
reducing agent prevents polymerization of resin monomers lightens darkened skin, light sensitive
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.]
Colorless to pale brown, odorless, hexagonal crystals
ChEBI: A benzenediol comprising benzene core carrying two hydroxy substituents para to each other.
K channel agonist, antihypertensive
No case reports of cancer associated
with HQ exposure have been published.
white needle-like crystals or crystalline powder
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.
Chemistry Letters, 14, p. 731, 1985The Journal of Organic Chemistry, 50, p. 1722, 1985Tetrahedron Letters, 22, p. 2337, 1981 DOI: 10.1016/S0040-4039(01)82900-2
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.
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).
Toxic by ingestion and inhalation, irritant.
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.