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BENZENE-1,4-DIOL

BENZENE-1,4-DIOL = HYDROQUINONE = 1,4-DIHYDROXYBENZENE = QUINOL

CAS Number: 123-31-9 
EC Number: 204-617-8
MDL number: MFCD00002339
Molecular Formula: C6H6O2 / C6H4-1,4-(OH)2

Benzene-1,4-diol, also known as Hydroquinone or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2. 
Benzene-1,4-diol has two hydroxyl groups bonded to a benzene ring in a para position. 
Benzene-1,4-diol is a white granular solid. 


Substituted derivatives of Benzene-1,4-diol are also referred to as hydroquinones. 
The name "hydroquinone" was coined by Friedrich Wöhler in 1843.
Benzene-1,4-diol  appears as light colored crystals or solutions.
Benzene-1,4-diol is a benzenediol comprising benzene core carrying two hydroxy substituents para to each other. 


Benzene-1,4-diol in some countries, including the member states of the European Union under Directives 76/768/EEC:1976.
Belongs to the class of organic compounds known as hydroquinone. 
Benzene-1,4-diol are compounds containing a hydroquinone moiety, which consists of a benzene ring with a hydroxyl groups at positions 1 and 4.
Benzene-1,4-diol or quinol, is an aromatic organic compound which is a type of phenol, having the chemical formula C6H4(OH)2. 

Benzene-1,4-diol's chemical structure has two hydroxyl groups bonded to a benzene ring in a para position. 
Benzene-1,4-diol is a white granular solid at room temperature and pressure.
Benzene-1,4-diol is the name recommended for Benzene-1,4-diol by the International Union of Pure and Applied Chemistry (IUPAC) in its 1993 Recommendations for the Nomenclature of Organic Chemistry. 
Benzene-1,4-diol can undergo mild oxidation to convert to the compound parabenzoquinone, C6H4O2, often called p-quinone or simply quinone. 


Reduction of quinone reverses this reaction back to Benzene-1,4-diol. 
Some biochemical compounds in nature have this sort of Benzene-1,4-diol  or quinone section in their structures, such as Coenzyme Q, and can undergo similar redox interconversions.
The hydroxyl groups of Benzene-1,4-diol are quite weakly acidic. 
Benzene-1,4-diol can lose an H+ from one of the hydroxyls to form a monophenolate ion or lose an H+ from both to form a diphenolate ion.


Benzene-1,4-diol is a benzenediol.
Benzene-1,4-diol is a hydroquinones.
Benzene-1,4-diol, also known as benzene-1,4-diol, is an aromatic organic compound which is a type of phenol, having the chemical formula C6H4(OH)2. 
Benzene-1,4-diol's chemical structure has two hydroxyl groups bonded to a benzene ring in a para position. 


Benzene-1,4-diol is a white granular solid at room temperature and pressure. 
The hydroxyl groups of Benzene-1,4-diol  are quite weakly acidic. 
Benzene-1,4-diol can lose an H+ from one of the hydroxyls to form a monophenolate ion or lose an H+ from both to form a diphenolate ion. 
Benzene-1,4-diol comprising benzene core carrying two hydroxy substituents para to each other.
Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2. 


Benzene-1,4-diol has two hydroxyl groups bonded to a benzene ring in a para position. 
Benzene-1,4-diol is a white granular solid. 
Substituted derivatives of Benzene-1,4-diol  are also referred to as hydroquinones. 
A white crystalline solid, C6H4(OH)2; r.d. 1.33; m.p. 170°C; b.p. 285°C. 


Benzene-1,4-diol, colourless, crystalline organic compound formed by chemical reduction of benzoquinone.
an aromatic organic compound that is a type of phenol, having the chemical formula C6H4(OH)2.
Benzene-1,4-diol is an aromatic organic compound which is a type of phenol. 
Benzene-1,4-diol can be considered a simple polyphenol. 


Substituted derivatives of this parent compound are also referred to as hydroquinone. 
Benzene-1,4-diol has a variety of uses principally associated with its action as a reducing agent which is soluble in water. 
Benzene-1,4-diol is a major component in most photographic developers where, with the compound Metol, Benzene-1,4-diol reduces silver halides to elemental silver. 


USES and APPLICATIONS of BENZENE-1,4-DIOL: 
-Benzene-1,4-diol is used as a topical treatment for skin hyperpigmentation and in various cosmetic products.
-Benzene-1,4-diol is produced as an inhibitor, an antioxidant, and an intermediate in the synthesis of dyes, motor fuels, and oils 
-Benzene-1,4-diol is used in photographic processing.


-Benzene-1,4-diol has a variety of uses principally associated with its action as a reducing agent that is soluble in water. 
-Benzene-1,4-diolis a major component in most black and white photographic developers for film and paper where, with the compound metol, Benzene-1,4-diol reduces silver halides to elemental silver.
-As a polymerisation inhibitor, exploiting its antioxidant properties, Benzene-1,4-diol prevents polymerization of acrylic acid, methyl methacrylate, cyanoacrylate, and other monomers that are susceptible to radical-initiated polymerization. 


-By acting as a free radical scavenger, Benzene-1,4-diol serves to prolong the shelflife of light-sensitive resins such as preceramic polymers.
-Benzene-1,4-diol can lose a hydrogen cation from both hydroxyl groups to form a diphenolate ion. 
-The disodium diphenolate salt of Benzene-1,4-diol is used as an alternating comonomer unit in the production of the polymer PEEK.
-Benzene-1,4-diol is used as a topical application in skin whitening to reduce the color of skin. 


-Benzene-1,4-diol  has a variety of uses principally associated with Benzene-1,4-diol's action as a reducing agent which is soluble in water. 
-Benzene-1,4-diol is a major component in most photographic developers where, with the compound Metol, Benzene-1,4-diol reduces silver halides to elemental silver.
-In human medicine, Benzene-1,4-diol is used as a topical application in skin whitening to reduce the color of skin as Benzene-1,4-diol does not have the same predisposition to cause dermatitis as Metol does. 
-The disodium diphenolate salt of Benzene-1,4-diol  is used as an alternating comonomer unit in the production of the polymer PEEK.


-As a polymerization inhibitor, Benzene-1,4-diol prevents polymerization of acrylic acid, methyl methacrylate, etc.
-Benzene-1,4-diol is also used as a raw material of herbicides, rubber antioxidants and dye stuffs.
-Benzene-1,4-diol has a variety of uses principally associated with its action as a reducing agent which is soluble in water. 


-Benzene-1,4-diol is a major component of most photographic developers where, with the compound Metol, it reduces silver halides to elemental silver.
-Benzene-1,4-diol  is commonly used as a biomarker for benzene exposure. 
-A substance that opposes oxidation or inhibits reactions brought about by dioxygen or peroxides.
-Any cosmetic used to lighten the colour of skin by reducing the concentration of melanin.


-Benzene-1,4-diol  has role Escherichia coli metabolite. 
-Benzene-1,4-diol has role antioxidant. 
-Benzene-1,4-diol has role cofactor.
-Benzene-1,4-diol  has role human xenobiotic metabolites. 


-Benzene-1,4-diol has role skin lightening agent.
-Benzene-1,4-diol is used in making dyes. 
-A white crystalline phenol, Benzene-1,4-diol, is used as an antioxidant, photographic developer, stabilizer, and reagent.
-A white crystalline soluble phenol used as a photographic developer; Benzene-1,4-diol.


-A white crystalline compound, C6H6O2, formed by the reduction of quinone, used chiefly in photography and to inhibit autoxidation reactions.
-In the field of water treatment, Benzene-1,4-diol is added to the hot water and cooling water of the closed-circuit heating and cooling system, and the corrosion inhibition of the water side Metal energy is carried out. 
-Benzene-1,4-diol is used as an oxygen scavenger for boiler water, and Benzene-1,4-diol is added thereto to remove residual dissolved oxygen when the boiler water is preheated for oxygen removal.


-Benzene-1,4-diol is a topical lightening product found in OTC products, and is used to correct skin discoloration associated with disorders of hyperpigmentation including melasma, post-inflammatory hyperpigmention, sunspots, and freckles. 
-Benzene-1,4-diol can be used alone, but is more frequently found in combination with other agents such as alpha-hydroxy acids, corticosteroids, retinoids, or sunscreen. 
-Benzene-1,4-diol is used as an OTC topical lightening agent for disorders of hyperpigmentation including melasma, post-inflammatory hyperpigmention, sunspots and freckles.


-The disodium diphenolate salt of Benzene-1,4-diol is used as an alternating comonomer unit in the production of the polymer PEEK. 
-In human medicine, Benzene-1,4-diol is used as a topical application in skin whitening to reduce the color of skin as Benzene-1,4-diol does not have the same predisposition to cause dermatitis as metol does. 
-Benzene-1,4-diol is also used as a raw material of herbicides, rubber antioxidants and dye stuffs.


PRODUCTION of BENZENE-1,4-DIOL:
Benzene-1,4-diol is produced industrially by two main routes.

*The most widely used route is similar to the cumene process in reaction mechanism and involves the dialkylation of benzene with propene to give 1,4-diisopropylbenzene. 
This compound reacts with air to afford the bis(hydroperoxide), which is structurally similar to cumene hydroperoxide and rearranges in acid to give acetone and hydroquinone.

*A second route involves hydroxylation of phenol over a catalyst. 
The conversion uses hydrogen peroxide and affords a mixture of hydroquinone and its ortho isomer catechol (benzene-1,2-diol):
C6H5OH + H2O2 → C6H4(OH)2 + H2O

Other, less common methods include:
A potentially significant synthesis of hydroquinone from acetylene and iron pentacarbonyl has been proposed Iron pentacarbonyl serves as a catalyst, rather than as a reagent, in the presence of free carbon monoxide gas. 
Rhodium or ruthenium can substitute for iron as the catalyst with favorable chemical yields but are not typically used due to their cost of recovery from the reaction mixture.
Hydroquinone and its derivatives can also be prepared by oxidation of various phenols. 

Examples include Elbs persulfate oxidation and Dakin oxidation.
Benzene-1,4-diol was first obtained in 1820 by the French chemists Pelletier and Caventou via the dry distillation of quinic acid.
Aniline is oxidized to p-benzoquinone with manganese dioxide in sulfuric acid medium and then reduced to hydroquinone with iron powder.


REACTIONS of BENZENE-1,4-DIOL:
The reactivity of Benzene-1,4-diol's hydroxyl groups resembles that of other phenols, being weakly acidic. 
The resulting conjugate base undergoes easy O-alkylation to give mono- and diethers. 

Similarly, hydroquinone is highly susceptible to ring substitution by Friedel–Crafts reactions such as alkylation. 
This reaction is exploited en route to popular antioxidants such as 2-tert-butyl-4-methoxyphenol (BHA). 
The useful dye quinizarin is produced by diacylation of hydroquinone with phthalic anhydride.


REDOX of BENZENE-1,4-DIOL:
Benzene-1,4-diol undergoes oxidation under mild conditions to give benzoquinone. 
This process can be reversed. 
Some naturally occurring hydroquinone derivatives exhibit this sort of reactivity, one example being coenzyme Q. 
Industrially this reaction is exploited both with hydroquinone itself but more often with its derivatives where one OH has been replaced by an amine.

When colorless hydroquinone and benzoquinone, a bright yellow solid, are cocrystallized in a 1:1 ratio, a dark-green crystalline charge-transfer complex (melting point 171 °C) called quinhydrone (C6H6O2·C6H4O2) is formed. 
This complex dissolves in hot water, where the two molecules dissociate in solution.


AMINATION of BENZENE-1,4-DIOL:
An important reaction is the conversion of Benzene-1,4-diol to the mono- and diamine derivatives. 
Methylaminophenol, used in photography, is produced in this way:
C6H4(OH)2 + CH3NH2 → HOC6H4NHCH3 + H2O

Diamines, useful in the rubber industry as antiozone agents, are similarly produced from aniline:
C6H4(OH)2 + 2 C6H5NH2 → C6H4(N(H)C6H5)2 + 2 H2O


NATURAL OCCURRENCES of BENZENE-1,4-DIOL:
Benzene-1,4-diol are one of the two primary reagents in the defensive glands of bombardier beetles, along with hydrogen peroxide (and perhaps other compounds, depending on the species), which collect in a reservoir. 
The reservoir opens through a muscle-controlled valve onto a thick-walled reaction chamber. 

This chamber is lined with cells that secrete catalases and peroxidases. 
When the contents of the reservoir are forced into the reaction chamber, the catalases and peroxidases rapidly break down the hydrogen peroxide and catalyze the oxidation of the Benzene-1,4-diols into p-quinones. 

These reactions release free oxygen and generate enough heat to bring the mixture to the boiling point and vaporize about a fifth of it, producing a hot spray from the beetle's abdomen.
It is also one of the chemical compounds found in castoreum. 
This compound is gathered from the beaver's castor sacs.
In bearberry (Arctostaphylos uva-ursi), arbutin is converted to hydroquinone.

REACTIONS KNOWN to PRODUCE BENZENE-1,4-DIOL:
4-aminophenol degradation :
4-aminophenol + H2O + H+ → benzene-1,4-diol + ammonium

4-hydroxyacetophenone degradation :
4-hydroxyphenylacetate + H2O → benzene-1,4-diol + acetate

4-nitrophenol degradation I :
1,4-benzoquinone + NADPH + H+ → benzene-1,4-diol + NADP+

echinenone and zeaxanthin biosynthesis (Synechocystis) :
all-trans-β-carotene + 2 1,4-benzoquinone + H2O → echinenone + 2 benzene-1,4-diol

Not in pathways:
arbutin-6-phosphate + H2O → β-D-glucose 6-phosphate + benzene-1,4-diol
4-hydroxybenzoate + NAD(P)H + oxygen + 2 H+ → CO2 + benzene-1,4-diol + NAD(P)+ + H2O


BENZENE-1,4-DIOL in NATURE:
White needle-like crystals. 
Soluble in alcohol and ether, soluble in water, slightly soluble in benzene. 
Visible light in the air easily turned to light red. 

The aqueous solution can be oxidized to Brown in air. 
Benzene-1,4-diol is a weak acid. 
Benzene-1,4-diol reacts with most of the oxidizing agents and is converted to O-and p-benzoquinones. 
Benzene-1,4-diol has a, beta and gamma; Three crystal forms. 

Type A is a triangular needle-like or diamond-like crystal, crystallized from water and stable. 
Lu is a triangular crystal, crystallized from methanol, unstable. 
The & gamma; Type is monoclinic crystal, which is obtained by sublimation method and is unstable. 
All three crystals can be rubbed to emit fluorescence. 
Benzene-1,4-diol is the flash point is high, the vapor pressure is low.


THE REASON FOR THE BOILING POINT of BENZENE-1,4-DIOL BEING HIGHER THAN THAT OF BENZENE-1,3-DIOL:
Benzene-1,4-diol has a boiling point of 287°C and Benzene-1,3-diol has a boiling point of 277°C and Benzene-1,2-diol has a boiling point of 245.5°C. 
This could be attributed to the ease of formation of 2 intermolecular hydrogen bonds with the 2 hydroxy groups of these molecules increasing when the hydroxy groups are placed apart, to minimise steric hindrance and repulsion. 
Benzene-1,4-diol could form intermolecular hydrogen bonds with more stability than Benzene-1,3-diol or Benzene-1,2-diol as these two will get destabilised by steric repulsion when large groups have to reach nearer to form hydrogen bonds.

Thus, the extent of intermolecular hydrogen bonding in : 
Benzene-1,4-diol > Benzene-1,3-diol > Benzene-1,2-diol
To overcome this attraction, more energy is needed. 
Hence the same is the order of their Boiling Points.


ALTERNATIVE PARENTS of BENZENE-1,4-DIOL:
*1-hydroxy-2-unsubstituted benzenoids 
*Benzene and substituted derivatives 
*Organooxygen compounds 
*Hydrocarbon derivatives 


SUBSTITUENTS of BENZENE-1,4-DIOL:
*Hydroquinone
*1-hydroxy-2-unsubstituted benzenoid
*Monocyclic benzene moiety
*Organic oxygen compound
*Hydrocarbon derivative
*Organooxygen compound
*Aromatic homomonocyclic compound


EXTERNAL DESCRIPTORS of BENZENE-1,4-DIOL:
*Hydroquinones 
*Benzenediol 
*An electron-transfer-related quinol 
*A benzenediol 


CATEGORIES of BENZENE-1,4-DIOL:    
*Antioxidants
*Benzene Derivatives
*Compounds used in a research, industrial, or household setting
*Depigmenting Agents
*Dermatologicals
*Melanin Synthesis Inhibitor
*Melanin Synthesis Inhibitors
*Mutagens
*Noxae
*Phenols
*Protective Agents
*Radiation-Protective Agents


PHYSICAL and CHEMICAL PROPERTIES of BENZENE-1,4-DIOL:
Molecular Weight: 110.11
Appearance Form: crystalline
Color: colorless
Odor: No data available
Odor Threshold: No data available
pH: 3,7 at 70 g/l
Melting point/freezing point:
Melting point/range: 172 - 175 °C - lit.
Initial boiling point and boiling range: 285 °C - lit.
Flash point: 165 °C at ca.1.013 hPa 


Evaporation rate: No data available
Flammability (solid, gas): The product is not flammable. 
Upper/lower flammability or explosive limits: No data available
Vapor pressure: 1 hPa at 132 °C
Vapor density: 3,80 - (Air = 1.0)
Density: 1,332 g/cm3 at 15 °C
Relative density: No data available
Water solubility 72 g/l at 25 °C - completely soluble
Partition coefficient: n-octanol/water
log Pow: 0,59 - Bioaccumulation is not expected.


Autoignition temperature: 515,56 °C at 1.013 hPa
Decomposition temperature: No data available
Viscosity 
Viscosity, kinematic: No data available
Viscosity, dynamic: No data available
Explosive properties: No data available
Oxidizing properties: No data available
Other safety information:
Relative vapor density: 3,80 - (Air = 1.0)


Water Solubility: 95.5 g/L    
logP: 0.71    
logP: 1.37    
logS: -0.06
pKa (Strongest Acidic): 9.68    
pKa (Strongest Basic): -5.9    
Physiological Charge: 0    
Hydrogen Acceptor Count: 2    
Hydrogen Donor Count: 2    
Polar Surface Area: 40.46 Ų    


Rotatable Bond Count: 0    
Refractivity: 30.02 m³·mol⁻¹    
Polarizability: 10.75 ų    
Number of Rings: 1    
Bioavailability: Yes    
Rule of Five: Yes    
Ghose Filter: No    
Veber's Rule: No    
MDDR-like Rule: No    


FIRST AID MEASURES of BENZENE-1,4-DIOL:
-Description of first-aid measures:
*General advice:
Show this material safety data sheet to the doctor in attendance.

*If inhaled
After inhalation: 
Fresh air. 
Call in physician.

*In case of skin contact: 
Take off immediately all contaminated clothing. 
Rinse skin with water/ shower. 
Consult a physician.

*In case of eye contact
After eye contact: 
Rinse out with plenty of water. 
Immediately call in ophthalmologist.
Remove contact lenses.

*If swallowed:
After swallowing: 
Immediately make victim drink water (two glasses at most). 
Consult a physician.

-Indication of any immediate medical attention and special treatment needed:
No data available


ACCIDENTAL RELEASE MEASURES of BENZENE-1,4-DIOL:
-Personal precautions, protective equipment and emergency procedures:
Advice for non-emergency personnel: 
Ensure adequate ventilation. 
Evacuate the danger area, observe emergency procedures, consult an expert.

-Environmental precautions:
Do not let product enter drains.

-Methods and materials for containment and cleaning up:
Cover drains. 
Collect, bind, and pump off spills. 
Observe possible material restrictions.
Take up dry. 
Dispose of properly. 
Clean up affected area. 


FIRE FIGHTING MEASURES of BENZENE-1,4-DIOL:
-Extinguishing media:
--Suitable extinguishing media:
Water Foam Carbon dioxide (CO2) 
Dry powder
--Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.

EXPOSURE CONTROLS/PERSONAL PROTECTION of BENZENE-1,4-DIOL:
-Control parameters:
--Ingredients with workplace control parameters:
-Exposure controls:
--Personal protective equipment:
*Eye/face protection:
Use safety goggles.

Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0,11 mm
Break through time: 480 min
Splash contact:
Material: Nitrile rubber
Minimum layer thickness: 0,11 mm
Break through time: 480 min

*Body Protection:
Use protective clothing.

-Control of environmental exposure:
Do not let product enter drains.


HANDLING and STORAGE of BENZENE-1,4-DIOL:
-Precautions for safe handling:
*Advice on safe handling:
Work under hood. 
Do not inhale substance/mixture.
*Hygiene measures:
Wash hands and face after working with substance.

-Conditions for safe storage, including any incompatibilities:
Storage conditions:
Tightly closed. 
Dry.


STABILITY and REACTIVITY of BENZENE-1,4-DIOL:
-Chemical stability
The product is chemically stable under standard ambient conditions (room temperature) .


SYNONYMS:
Hydroquinone
Idrochinone
Quinol
1,4-Dihydroxybenzene
p-dihydroxybenzene
1,4-Hydroxy benzene
1,4-Benzenediol
HQ
1,4-Dihydroxybenzene
Hydroquinone
Quinol
P-Hydroquinone
Hydrochinon
Dihydroquinone
Hydroquinol
Benzoquinol
Hydrochinone
Hidroquinone
Hidroquin
Idrochinone
Para-Hydroquinone
Hydroquinole
Hidroquilaude
1, 4-Dihydroxy-Benzeen
1, 4-Diidrobenzene
Pyrogentistic Acid
Hydroquinoue
Ccris 714
Diak 5
1,4-Benzenediol    
1,4-Dihydroxybenzene    
4-Hydroxyphenol    
Benzene-1,4-diol    
Eldoquin    
Hydroquinone    
hydroquinone    
p-Benzenediol    
p-Hydroquinone    
p-hydroxyphenol    
Quinol
1,4-benzenediol
benzene-1,4-diol
p-dihydroxybenzene
1,4-dihydroxybenzene
hydroquinol
p-hydroquinone

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