123-31-9

Basic information

• Product Name: Hydroquinone
• Synonyms: Hydroquinone, 99.5%, 99.5%;Hydrochinone 0;Hydroquinone ReagentPlus(R), >=99.5%;HYDROQUINONE GPR RECTAPUR;PHOTO GRADE Hydroquinone;HYDROQUINONE PHOTO GRADE 99%;p-Benzediel p-Dihydroxybenzene Hydroquinol 1,4-Benzenediol 1,4-Dihydroxybenzene Quinol;Hydroquinone, p.a.
• CAS NO: 123-31-9
• Molecular Formula: C₆H₆O₂
• Molecular Weight: 110.11
• EINECS: 204-617-8
• Product Categories: PINDAC;Intermediates of Dyes and Pigments;Redox Catalysts (Environmentally-friendly Oxidation);Environmentally-friendly Oxidation;Synthetic Organic Chemistry;Aromatics;Building Blocks;Chemical Synthesis;Nutrition Research;Organic Building Blocks;Oxygen Compounds;Phytochemicals by Plant (Food/Spice/Herb);Polyols;Vaccinium myrtillus (Bilberry);corrosion inhibitor
• Mol File: 123-31-9.mol
• Article Data: 644

Chemical Properties

• Melting Point: 172-175 °C(lit.)
• Boiling Point: 285 °C(lit.)
• Flash Point: 165 °C
• Appearance: White to off-white/Needle-Like Crystals or Crystalline Powder
• Density: 1.32
• Vapor Density: 3.81 (vs air)
• Vapor Pressure: 1 mm Hg ( 132 °C)
• Refractive Index: 1.6320
• Storage Temp.: Refrigerator
• Solubility: H2O: 50 mg/mL, clear
• PKA: 10.35(at 20℃)
• Water Solubility: 70 g/L (20 ºC)
• Sensitive: Air & Light Sensitive
• Stability: Stable. Combustible. Incompatible with strong oxidizing agents, strong bases, oxygen, ferric salts. Light and air-sensitive. Dis
• Merck: 14,4808
• BRN: 605970
• CAS DataBase Reference: Hydroquinone(CAS DataBase Reference)
• NIST Chemistry Reference: Hydroquinone(123-31-9)
• EPA Substance Registry System: Hydroquinone(123-31-9)

Safety Data

• Hazard Codes: Xn,N
• 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
• TSCA: Yes
• HazardClass: 9
• PackingGroup: III
• Hazardous Substances Data: 123-31-9(Hazardous Substances Data)

Usage

Chemical Description

Hydroquinone and toluhydroquinone are organic compounds that are used in the production of photographic developers, antioxidants, and polymerization inhibitors.

Description

Hydroquinone (HQ) is produced by the oxidation of aniline or phenol, by the reduction of quinone, or from a reaction of acetylene and carbon monoxide. Hydroquinone occurs naturally as a glucose ether, also known as arbutin, in the leaves of many plants and in fruits, as well as one of the agents used in the defense mechanism of the bombardier beetle, family Carabidae.

Chemical Properties

Different sources of media describe the Chemical Properties of 123-31-9 differently. You can refer to the following data:
1. white needle-like crystals or crystalline powder
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.

Physical properties

Colorless to pale brown, odorless, hexagonal crystals

Originator

Quinnone,Dermohr,US,1980

Uses

Different sources of media describe the Uses of 123-31-9 differently. You can refer to the following data:
1. Use as photographic reducer and developer; as reagent in the determination of small quantities of phosphate; as antioxidant. Depigmentor
2. 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.
3. K channel agonist, antihypertensive
4. reducing agent prevents polymerization of resin monomers lightens darkened skin, light sensitive
5. Photographic reducer and developer; antioxidant; stabilizing agent for some polymers; intermediate in the manufacturing of some dyes and pigments; in cosmetic formulations.

Definition

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

Indications

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

Depigmentor

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, 1985The Journal of Organic Chemistry, 50, p. 1722, 1985Tetrahedron 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)

Hazard

Toxic by ingestion and inhalation, irritant. Questionable carcinogen.

Health Hazard

Different sources of media describe the Health Hazard of 123-31-9 differently. You can refer to the following data:
1. 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.
2. 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.

Flammability and Explosibility

Nonflammable

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.

Carcinogenicity

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

Source

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.]

Toxicity evaluation

Benzene, phenol, and hydroquinone are metabolized in vivo to benzoquinone and excreted as the mercapturate, N-acetyl-S- (2,5-dihydroxyphenyl)-L-cysteine. Hydroquinone is a reducing cosubstrate for peroxidase enzymes, and the resultant semiquinone and p-benzoquinone may bind to DNA.

InChI:InChI=1/C9H6O4/c10-6-3-5-1-2-9(12)13-8(5)4-7(6)11/h1-4,10-11H

Synthetic route

p-benzoquinone (106-51-4) → hydroquinone (123-31-9)

Conditions	Yield
With nickel In tetrahydrofuran at 20℃; for 0.166667h; Reduction;	100%
With boron trifluoride diethyl etherate; sodium iodide In acetonitrile at 0℃; for 0.0833333h;	99%
With hydrazine hydrate In acetonitrile at 20℃; for 18h; Irradiation;	99%

4-Benzyloxyphenol (103-16-2) → hydroquinone (123-31-9)

Conditions	Yield
With palladium 10% on activated carbon; hydrogen In methanol at 50℃; under 750.075 Torr; Reagent/catalyst; Flow reactor;	100%
With hydrogen In methanol at 20℃; under 760.051 Torr; for 18h; Reagent/catalyst; chemoselective reaction;	100%
With hydrogen In methanol at 20℃; for 6h; chemoselective reaction;	100%
Multi-step reaction with 3 steps 1: potassium carbonate, potassium iodide / acetonitrile / 1 h / Heating 2: 84 percent / hydrogen / 10percent palladium on carbon / tetrahydrofuran; ethanol / 3 h / 760 Torr 3: 88 percent / hydrogen / 10percent palladium on carbon / ethanol / 15 h / 3040 Torr View Scheme
With formic acid for 3h; Heating / reflux;

1,4-dibenzyloxybenzene (621-91-0) → hydroquinone (123-31-9)

Conditions	Yield
With hydrogen In tetrahydrofuran; carbon dioxide at 50℃; under 75007.5 Torr; gas-expanded solution;	100%

dimethanesulfonate hydroquinone (126150-65-0) → hydroquinone (123-31-9)

Conditions	Yield
With sodium phosphate In aq. phosphate buffer; water; dimethyl sulfoxide at 25℃; for 0.333333h; pH=7.5; Enzymatic reaction;	100%

1,4-dimethoxybezene (150-78-7) → hydroquinone (123-31-9)

Conditions	Yield
With hydrogenchloride In water at 250℃; under 37503.8 Torr; for 3h; Autoclave; Inert atmosphere; Green chemistry;	98%
With hydrogen iodide at 25℃; for 24h; Inert atmosphere;	96%
With lithium triethylborohydride In tetrahydrofuran at 67℃; for 168h;	90%

4-hydroxy-benzaldehyde (123-08-0) → hydroquinone (123-31-9)

Conditions	Yield
With dihydrogen peroxide at 20℃; for 0.666667h; Dakin Phenol Oxidation; Green chemistry;	98%
With dihydrogen peroxide In water at 20℃; for 2h; Dakin Phenol Oxidation; Green chemistry;	98%
With dihydrogen peroxide; 5-ethyl-10-methyl-2,4-dioxo-2,3,4,10-tetrahydrobenzo[g]pteridin-5-ium perchlorate; sodium hydrogencarbonate In methanol; water at 20℃; for 24h; Reagent/catalyst; Dakin Phenol Oxidation; chemoselective reaction;	97%

hydrazine hydroquinone complex (97108-34-4) + 4-hydroxy-benzaldehyde (123-08-0) → bis(4-hydroxybenzylidene)hydrazine (5466-23-9) + hydroquinone (123-31-9)

Conditions	Yield
at 25 - 30℃; for 1h; Product distribution; Further Variations:; Reaction partners; Reaction types; Condensation; solid state, in ball mill;	A 98% B n/a

(p-hydroxyphenyl)boronic acid (71597-85-8) → hydroquinone (123-31-9)

Conditions	Yield
With 2,5-dimethylfuran; zinc(II) phthalocyanine; oxygen In tetrahydrofuran at 25℃; under 760.051 Torr; for 1.5h; Irradiation; Sealed tube; Schlenk technique;	98%
With 1-carboxymethyl-3-methylimidazolium tetrachloroferrate; dihydrogen peroxide In neat (no solvent) at 20℃; for 0.116667h;	95%
With iron(III) oxide; oxygen In tetrahydrofuran Irradiation;	91%

1,4-bis(trimethylsilyloxy)benzene (2117-24-0) → hydroquinone (123-31-9)

Conditions	Yield
With methanol; 1,3-disulfonic acid imidazolium hydrogen sulfate at 20℃; for 0.0833333h; Green chemistry;	98%

p-benzoquinone (106-51-4) + 2-mesitylmagnesium bromide (2633-66-1) → 4-hydroxy-4-(2,4,6-trimethylphenyl)-2,5-cyclohexadiene + hydroquinone (123-31-9) + 1,3,5-trimethyl-benzene (108-67-8)

Conditions	Yield
In tetrahydrofuran Grignard reaction;	A 97% B 3% C 4%

p-Coumaric Acid (7400-08-0) → hydroquinone (123-31-9)

Conditions	Yield
With NADH In aq. phosphate buffer at 37℃; for 8h; pH=7.0; Enzymatic reaction;	97%
Multi-step reaction with 3 steps 1.1: feruloyl-CoA synthetase / Enzymatic reaction 1.2: Enzymatic reaction 2.1: vanillin dehydrogenase from genom of Pseudomonas putida KT2440 (NC_002947.4) / Enzymatic reaction 3.1: 4-hydroxybenzoate 1-hydroxylase MNX1 from yeast Candida parapsilosis strain CDC317 / 2 h / Enzymatic reaction View Scheme
Multi-step reaction with 3 steps 1: E. coli (pET28a-TtAdo-BLPad) / aq. phosphate buffer / 6 h / 37 °C / pH 7.0 / Enzymatic reaction 2: vanillin dehydrogenase from genom of Pseudomonas putida KT2440 (NC_002947.4) / Enzymatic reaction 3: 4-hydroxybenzoate 1-hydroxylase MNX1 from yeast Candida parapsilosis strain CDC317 / 2 h / Enzymatic reaction View Scheme
Multi-step reaction with 4 steps 1: Bacillus licheniformis strain CGMCC 7172 phenolic acid decarboxylase / 6 h / Enzymatic reaction 2: oxygen; Thielavia terrestris NRRL 8126 aromatic dioxygenase TtAdo (XP_003653923) / 37 °C / pH 7.0 / Enzymatic reaction 3: vanillin dehydrogenase from genom of Pseudomonas putida KT2440 (NC_002947.4) / Enzymatic reaction 4: 4-hydroxybenzoate 1-hydroxylase MNX1 from yeast Candida parapsilosis strain CDC317 / 2 h / Enzymatic reaction View Scheme

sec.-butyllithium (598-30-1) + p-benzoquinone (106-51-4) → hydroquinone (123-31-9) + 4-sec-Butyl-4-hydroxy-cyclohexa-2,5-dienone

Conditions	Yield
In tetrahydrofuran at -78℃; for 0.5h;	A 96% B 4%

1,4-Phenyldiboronic acid (4612-26-4) → hydroquinone (123-31-9)

Conditions	Yield
With urea hydrogen peroxide adduct In methanol at 27 - 29℃; for 0.0833333h; Green chemistry; chemoselective reaction;	96%
With LACTIC ACID; dihydrogen peroxide In water at 20℃; for 0.166667h; Reagent/catalyst; Green chemistry;	95%
With dihydrogen peroxide In ethanol at 20℃; for 0.166667h;	91%

benzene (71-43-2) → hydroquinone (123-31-9)

Conditions	Yield
With dihydrogen peroxide; copper(II) nitrate In phosphate buffer; acetonitrile at 50℃; Oxidation;	95%
With dihydrogen peroxide; vanadia In water; acetic acid; acetonitrile at 59.84℃; for 6h; Green chemistry;	4.1%
With ethanol; sulfuric acid Electrolysis;

1,4-bis{[(tert-butyl)(dimethyl)silyl]oxy}benzene (78018-57-2) → hydroquinone (123-31-9)

Conditions	Yield
With aluminium(III) chloride hexahydrate In methanol at 50℃; for 12h; Solvent; Temperature; Heating; Sealed tube; chemoselective reaction;	95%
With cerium (IV) sulfate tetrahydrate In methanol at 130℃; for 0.333333h; Microwave irradiation;	93%
With dichloro bis(acetonitrile) palladium(II) In water; acetone at 75℃; for 19h;	79%
With potassium hydrogen difluoride In methanol at 20℃; for 1h;	67%
With copper(ll) sulfate pentahydrate In methanol at 100℃; for 0.25h; Microwave irradiation;	64%

p-benzoquinone (106-51-4) + CH3MgX → 4-hydroxy-4-methyl-cyclohexa-2,5-dienone (23438-23-5) + hydroquinone (123-31-9)

Conditions	Yield
In tetrahydrofuran at -78℃; for 0.5h;	A 95% B n/a

p-benzoquinone (106-51-4) + (C2H5)(CH3)CHMgX → hydroquinone (123-31-9) + 4-sec-Butyl-4-hydroxy-cyclohexa-2,5-dienone

Conditions	Yield
In tetrahydrofuran at -78℃; for 0.5h;	A 95% B 5%

phenylmagnesium bromide + p-benzoquinone (106-51-4) → 4-hydroxy-4-phenyl-cyclohexa-2,5-dienone (42860-77-5) + hydroquinone (123-31-9) + benzene (71-43-2)

Conditions	Yield
In tetrahydrofuran Grignard reaction;	A 94% B 3% C 3%

phenol (108-95-2) → maleic anhydride (108-31-6) + succinic acid (110-15-6) + hydroquinone (123-31-9)

Conditions	Yield
With sulfuric acid; water; oxygen; titanium silicalite 1 (TS-1) at 65℃; for 4 - 6h; pH=~ 1.2 - 1.8; Product distribution / selectivity; Electrolysis;	A n/a B n/a C 93.4%

4-isopropenylphenol (4286-23-1) → hydroquinone (123-31-9)

Conditions	Yield
	93.3%
With hydrogenchloride; dihydrogen peroxide at 20 - 40℃; for 0.583333h; Product distribution; other alkenyl phenols;	91%
With sulfuric acid; dihydrogen peroxide; sodium sulfite In acetone

4-methoxy-phenol (150-76-5) → hydroquinone (123-31-9)

Conditions	Yield
With Cyclohexyl iodide In N,N-dimethyl-formamide for 3h; Product distribution; Further Variations:; Reagents; Solvents; Temperatures; time; Heating;	93%
With water; hydrogen bromide; Aliquat 336 at 105℃; for 7h; Catalytic behavior;	85%
With 1-butylpyridinium bromide at 100℃; Microwave irradiation; Neat (no solvent);	77%

cyclohexylamine (108-91-8) + (1-butyl)-(-4-oxy-phenylene) carbonate (81577-19-7) → butyl N-cyclohexylcarbamate (17671-80-6) + hydroquinone (123-31-9)

Conditions	Yield
With N,N-dimethyl-formamide	A 92% B n/a

4-(1-cyclopenten-1-yl)phenol (877-46-3) → cyclopentanone (120-92-3) + hydroquinone (123-31-9)

Conditions	Yield
With hydrogenchloride; dihydrogen peroxide In acetonitrile at 50℃; for 3h; the excess of H2O2 was removed by catalytic hydrogenation using 10percent Pd-C;	A n/a B 91.6%

p-benzoquinone (106-51-4) + (CH3)2CHMgX → hydroquinone (123-31-9) + 4-hydroxy-4-isopropylcyclohexa-2,5-dien-1-one

Conditions	Yield
In tetrahydrofuran at -78℃; for 0.5h;	A 90% B 10%

p-benzoquinone (106-51-4) → hydroquinone (123-31-9) + phenol (108-95-2)

Conditions	Yield
With cyclohexanone; cyclohexanol at 115℃; for 9h; Catalytic behavior; Reagent/catalyst; Temperature; Inert atmosphere;	A 90% B 4.3 g

methyl 5-phenylcyclohexane-1,3-dione (18986-66-8) → hydroquinone (123-31-9)

Conditions	Yield
With iodine; dimethyl sulfoxide at 80℃; for 24h; Sealed tube; Green chemistry;	90%

acetic anhydride (108-24-7) + hydroquinone (123-31-9) → benzene-1,4-diyl diacetate (1205-91-0)

Conditions	Yield
With magnesium(II) perchlorate at 20℃; for 0.16h;	100%
With tin(IV) tetraphenylporphyrin perchlorate at 20℃; for 0.0833333h;	99%
beta zeolite H-form at 20℃; for 2h;	99%

hydroquinone (123-31-9) → p-benzoquinone (106-51-4)

Conditions	Yield
With barium ferrate(VI) In benzene for 0.25h; Product distribution; Heating;	100%
With benzyltrimethylammonium tribromide; sodium acetate In dichloromethane; water for 2h; Ambient temperature;	100%
With bis(2,2'-bipyridyl) copper(II) permanganate In dichloromethane for 0.25h; Ambient temperature;	100%

3,4-dihydro-2H-pyran (110-87-2) + hydroquinone (123-31-9) → 2-(4-(tetrahydro-2H-pyran-2-yloxy)phenoxy)tetrahydro-2H-pyran (2139-44-8)

Conditions	Yield
With pyridinium p-toluenesulfonate In dichloromethane for 3h;	100%
With pyridinium p-toluenesulfonate In dichloromethane at 25℃; for 2h;	100%
With pyridinium p-toluenesulfonate In dichloromethane at 20℃; for 48h;	99%

propargyl bromide (106-96-7) + hydroquinone (123-31-9) → 1,4-bis(prop-2-yn-1-yloxy)benzene (34596-36-6)

Conditions	Yield
Stage #1: hydroquinone With potassium carbonate In acetone for 0.5h; Reflux; Stage #2: propargyl bromide In acetone for 12h; Reflux;	100%
Stage #1: hydroquinone With 18-crown-6 ether; potassium carbonate In acetonitrile for 0.5h; Reflux; Inert atmosphere; Stage #2: propargyl bromide In toluene; acetonitrile Reflux; Inert atmosphere;	98%
Stage #1: hydroquinone With potassium carbonate In acetone for 0.5h; Stage #2: propargyl bromide In acetone for 20h; Reflux;	96%

2-[2-(chloroethoxy)ethoxy]ethanol (5197-62-6) + hydroquinone (123-31-9) → 1,4-bis-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)benzene (134881-72-4)

Conditions	Yield
With potassium tert-butylate In tert-butyl alcohol for 92h; Heating;	100%
With potassium tert-butylate In tert-butyl alcohol for 65h; Heating;	78%
With potassium carbonate In acetonitrile at 130℃; for 72h; Sealed tube; High pressure;	75%

pentafluorosulfanyl isocyanate (2375-30-6) + hydroquinone (123-31-9) → 1,4-Phenylene Bis<(pentafluorosulfanyl)carbamate> (90597-97-0)

Conditions	Yield
In acetone -196 deg C to r.t.;	100%

C14H20O4 (134637-27-7) + hydroquinone (123-31-9) → C20H24O6 (134637-24-4)

Conditions	Yield
With silver(l) oxide Ambient temperature;	100%

hydroquinone (123-31-9) → diphenyl-2,5 furannedicarbaldehyde 3,4 (36831-87-5) + p-benzoquinone (106-51-4)

Conditions	Yield
With barium ferrate(VI) In benzene for 0.3h; Heating;	A 70% B 100%

3,5-dibenzyloxylbenzoyl chloride (28917-44-4) + hydroquinone (123-31-9) → C48H38O8 (159507-52-5)

Conditions	Yield
With dmap In dichloromethane for 120h; Ambient temperature;	100%

bis(diethylamino)phenylphosphine (1636-14-2) + hydroquinone (123-31-9) → p-phenylene bis(N,N-diethyl-P-phenylphosphonamidite)

Conditions	Yield
at 115 - 120℃; for 2.5h;	100%
In acetonitrile

2,3-dihydroxynaphthalene-6-sulphonic acid sodium salt (135-53-5) + hydroquinone (123-31-9) + 1,3-bis(4'-fluorobenzoyl)benzene (108464-88-6) → Polymer; Monomer(s): 1,3-bis(4-fluorobenzoyl)benzene, 5 mmol; sodium 6,7-dihydroxy-2-naphthalenesulfonate, 4.5 mmol; hydroquinone, 0.5 mmol

Conditions	Yield
With potassium carbonate In 1-methyl-pyrrolidin-2-one at 160 - 170℃;	100%

2,3-dihydroxynaphthalene-6-sulphonic acid sodium salt (135-53-5) + hydroquinone (123-31-9) + 1,3-bis(4'-fluorobenzoyl)benzene (108464-88-6) → Polymer; Monomer(s): 1,3-bis(4-fluorobenzoyl)benzene, 5 mmol; sodium 6,7-dihydroxy-2-naphthalenesulfonate, 4 mmol; hydroquinone, 1 mmol

Conditions	Yield
With potassium carbonate In 1-methyl-pyrrolidin-2-one at 160 - 170℃;	100%

2,3-dihydroxynaphthalene-6-sulphonic acid sodium salt (135-53-5) + hydroquinone (123-31-9) + 1,3-bis(4'-fluorobenzoyl)benzene (108464-88-6) → Polymer; Monomer(s): 1,3-bis(4-fluorobenzoyl)benzene, 5 mmol; sodium 6,7-dihydroxy-2-naphthalenesulfonate, 3.5 mmol; hydroquinone, 1.5 mmol

Conditions	Yield
With potassium carbonate In 1-methyl-pyrrolidin-2-one at 160 - 170℃;	100%

2,3-dihydroxynaphthalene-6-sulphonic acid sodium salt (135-53-5) + hydroquinone (123-31-9) + 1,3-bis(4'-fluorobenzoyl)benzene (108464-88-6) → Polymer; Monomer(s): 1,3-bis(4-fluorobenzoyl)benzene, 5 mmol; sodium 6,7-dihydroxy-2-naphthalenesulfonate, 3 mmol; hydroquinone, 2 mmol

Conditions	Yield
With potassium carbonate In 1-methyl-pyrrolidin-2-one at 160 - 170℃;	100%

2,3-dihydroxynaphthalene-6-sulphonic acid sodium salt (135-53-5) + hydroquinone (123-31-9) + 1,3-bis(4'-fluorobenzoyl)benzene (108464-88-6) → Polymer; Monomer(s): 1,3-bis(4-fluorobenzoyl)benzene, 5 mmol; sodium 6,7-dihydroxy-2-naphthalenesulfonate, 2.5 mmol; hydroquinone, 2.5 mmol

Conditions	Yield
With potassium carbonate In 1-methyl-pyrrolidin-2-one at 160 - 170℃;	100%

6-chloro-2-(2,6-diisopropylphenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (852282-88-3) + hydroquinone (123-31-9) → C30H27NO4 (923584-43-4)

Conditions	Yield
With potassium carbonate In 1-methyl-pyrrolidin-2-one at 80℃; for 24h;	100%

hydroquinone (123-31-9) + 1,1,3,3-tetramethyldisilazane (15933-59-2) → 1,4-bis(dimethylsilyloxy)benzene (70939-99-0)

Conditions	Yield
With dimethylmonochlorosilane In tetrahydrofuran Reflux;	100%

hydroquinone (123-31-9) + tert-butyl alcohol (75-65-0) → tert-butylhydroquinone (1948-33-0)

Conditions	Yield
With phosphoric acid In water at 59 - 81℃; for 2h; Temperature;	99.9%
With aminosulfonic acid In 1,4-dioxane; toluene at 135℃; for 8h; Temperature;	50%
With phosphoric acid In water at 80℃; for 4h; Concentration; Temperature; Time; Large scale;	44.8%

acetic acid tert-butyl ester (540-88-5) + hydroquinone (123-31-9) → tert-butylhydroquinone (1948-33-0)

Conditions	Yield
With sulfuric acid at 85℃; for 8h; Temperature; Large scale;	99.9%

oxirane (75-21-8) + hydroquinone (123-31-9) → 1,4-bis(2-hydroxyethoxy)benzene (104-38-1)

Conditions	Yield
Stage #1: hydroquinone With 1,1'-bis-(diphenylphosphino)ferrocene In diethylene glycol dimethyl ether at 100℃; Autoclave; Inert atmosphere; Stage #2: oxirane In diethylene glycol dimethyl ether at 130 - 135℃; for 4h; Solvent; Temperature;	99.3%
anion exchange resin A (Cl-type) In 2-methoxy-ethanol; toluene at 100℃; for 6h;	73%
anion exchange resin A (Cl-type) In 2-methoxy-ethanol at 100℃; for 4.5h;	69 %Chromat.

2-bromoisobutyric acid bromide (20769-85-1) + hydroquinone (123-31-9) → 1,4-phenylene bis(2-bromo-2-methylpropanoate)

Conditions	Yield
With triethylamine In tetrahydrofuran for 6.5h; Cooling with ice;	99.2%
With triethylamine In tetrahydrofuran at 0 - 20℃; Inert atmosphere;	86.8%
With triethylamine In tetrahydrofuran for 24h;

hydroquinone (123-31-9) → 1,4-Cyclohexanediol (556-48-9)

Conditions	Yield
With hydrogen In water at 30℃; under 7500.75 Torr; for 7h; Autoclave;	99.1%
With hydrogen In water at 80℃; under 15001.5 Torr; for 6h;	99%
With potassium hydroxide; samarium diiodide In tetrahydrofuran; water for 0.05h; Ambient temperature;	98%

acetic acid (64-19-7) + hydroquinone (123-31-9) → benzene-1,4-diyl diacetate (1205-91-0)

Conditions	Yield
With bismuth(lll) trifluoromethanesulfonate for 1h; Heating;	99%
With poly(4-vinylpyridine) perchlorate In neat (no solvent) at 20℃; for 0.366667h;	92%
With PPA

allyl bromide (106-95-6) + hydroquinone (123-31-9) → 1,4-bis(allyloxy)benzene (37592-20-4)

Conditions	Yield
Stage #1: allyl bromide With sodium hydride In N,N-dimethyl-formamide; oil at -10℃; for 0.166667h; Stage #2: hydroquinone In N,N-dimethyl-formamide; oil for 0.75h;	99%
With potassium carbonate In acetone for 5h; Heating;	95%
With potassium carbonate In acetone Reflux;	90%

Upstream product

• 591-50-4 iodobenzene 
• 64-17-5 ethanol 
• 104-91-6 p-nitrosophenol 
• 488-73-3 (+)-proto-quercitol 
• 533-73-3 1,2,4-Trihydroxybenzene 
• 35616-03-6 4-hydroxyphenyl 4-methyl-1-benzenesulfonate 
• 3786-46-7 3,6-dihydroxyphthalic acid 
• 106-34-3 quinhydrone 
• 68-11-1 mercaptoacetic acid 
• 106-51-4 p-benzoquinone 
• 95-57-8 2-monochlorophenol 
• 106-48-9 4-chloro-phenol 
• 67-63-0 isopropyl alcohol 
• 65-85-0 benzoic acid 

Downstream Products

• 743401-30-1 ethyl-trisulfane 
• 26750-45-8 2-(2-ethylsulfanyl-ethylsulfanyl)-ethanethiol 
• 1521-04-6 2,5-di-piperidin-1-yl-[1,4]benzoquinone 
• 80-62-6 methacrylic acid methyl ester 
• 2206-94-2 1-acetoxy-1-phenylethene 
• 475-38-7 5,8-Dihydroxy-1,4-naphthoquinone 
• 75350-29-7 furan-2-carboxylic acid-(4-hydroxy-phenyl ester) 
• 75741-99-0 1,4-bis-(furan-2-carbonyloxy)-benzene 
• 14918-69-5 2,3-dichloro-5,8-dihydroxy-[1,4]naphthoquinone 
• 3712-11-6 6,9-dihydroxybenzoquinoline-5,10-quinone 
• 7475-11-8 1,4,6-trihydroxyanthracene-9,10-dione 
• 1220-95-7 6-chloroquinizarin 
• 245064-92-0 1,4-dihydroxy-5-chloro-9,10-anthraquinone 
• 1225-15-6 6,7-dichloro-1,4-dihydroxy-9,10-anthraquinone 

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Synthesis of renewable C-C cyclic compounds and high-density biofuels using 5-hydromethylfurfural as a reactant

The major challenge in the synthesis of high-density biofuels is to identify the bio-based source for C-C cyclic compounds and C-C coupling reactions with a suitable selectivity. Herein, we selectively synthesize 1,2,4-benzenetriol (BTO) with a yield of 51.4% from cellulose-derived 5-hydromethylfurfural via a ring-rearrangement reaction. The cellulose-derived route is a more meaningful route for the C-C cyclic compounds compared to the traditional hemicellulose- and lignin-derived routes. Furthermore, BTO is very easily dimerized via a C-C oxidative coupling reaction, showing a yield of 94.4% and selectivity of nearly 100% under environmentally friendly reaction conditions. After hydrodeoxygenation, bicyclohexane is obtained with a yield of 87.4%. This work not only provides a promising route to produce C-C cyclic fine compounds based on a cellulose-derived route, but also shows a highly efficient synthesis route for high-density biofuels via the C-C oxidative coupling reaction.

Oxygen-vacancy-promoted catalytic wet air oxidation of phenol from MnO: X-CeO2

Catalytic oxidation can be effectively promoted by the presence of oxygen vacancies on the catalyst surface. In this study, the effect of oxygen vacancies on the catalytic wet air oxidation (CWAO) of phenol was investigated with CeO2 and MnOx-CeO2 as catalysts. CeO2 and MnOx-CeO2 catalysts with different amounts of oxygen vacancies were obtained via hydrothermal methods and applied for the CWAO of phenol. It was found that CeO2 and MnOx-CeO2 nanorods were much more active than the cubic nanorods. The physicochemical properties of the samples were characterized by TEM, XRD, BET, XPS, and H2-TPR techniques. The results revealed that the presence of oxygen vacancies in CeO2 and MnOx-CeO2 catalysts could increase the oxidizing ability of the catalysts surface. The addition of Mn could greatly improve the adsorption ability of CeO2 and more efficiently oxidize phenol and its intermediates. The synergy between Mn and Ce could further improve the catalyst redox properties and produce a larger amount of active oxygen species, which is the reason why MnOx-CeO2 nanorods are the most active catalysts among the catalysts investigated in this study.

Purification and characterization of a naringinase from Aspergillus aculeatus JMUdb058

A naringinase from Aspergillus aculeatus JMUdb058 was purified, identified, and characterized. This naringinase had a molecular mass (MW) of 348 kDa and contained four subunits with MWs of 100, 95, 84, and 69 kDa. Mass spectrometric analysis revealed that the three larger subunits were β-d-glucosidases and that the smallest subunit was an α-l-rhamnosidase. The naringinase and its α-l-rhamnosidase and β-d-glucosidase subunits all had optimal activities at approximately pH 4 and 50 C, and they were stable between pH 3 and 6 and below 50 C. This naringinase was able to hydrolyze naringin, aesculin, and some other glycosides. The enzyme complex had a Km value of 0.11 mM and a kcat/Km ratio of 14 034 s-1 mM -1 for total naringinase. Its α-l-rhamnosidase and β-d-glucosidase subunits had Km values of 0.23 and 0.53 mM, respectively, and kcat/Km ratios of 14 146 and 7733 s -1 mM-1, respectively. These results provide in-depth insight into the structure of the naringinase complex and the hydrolyses of naringin and other glycosides.

A highly selective photooxidation approach using O2 in water catalyzed by iron(II) bipyridine complex supported on NaY zeolite

A new photocatalytic system involving iron(II) bipyridine supported on NaY zeolite (FeBY) shows excellent reactivity and selectivity in the oxidation of organic compounds. This approach allows highly controlled oxidation reaction to occur but avoids undesirable mineralization into CO2 and H 2O.

High-pressure Kinetics of the Reaction of p-Benzoquinone with Di-n-butylamine in Some Aprotic Solvents

The kinetics and the volume of activation of the title reaction to form 2-dibutylamino-p-benzoquinone in 1,2-dichloroethane and acetonitrile, -54 +/- 2 and -67 +/- 2 cm3/mol respectively, strongly support a reaction scheme in which ionic species are formed prior to the rate-determining step which is the second attack by the amine.

Cooperative structure direction of organosilanes and tetrapropylammonium hydroxide to generate hierarchical ZSM-5 zeolite with controlled porous structure

Hierarchical ZSM-5 zeolite with short-range ordered mesoporosity and hierarchical ZSM-5 zeolite nanorods were obtained via a direct hydrothermal synthesis by the cooperative structure direction of dimethyloctadecyl[3-(trimethoxysilyl)propyl]- ammonium chloride (TPOAC) and tetrapropylammonium hydroxide (TPAOH). Dimethyloctadecyl[3-(dimethoxymethylsilyl)propyl]ammonium chloride (DPOAC) and octadecyltrimethylammonium chloride (OTAC) were also employed as structure directing agents (SDA) to further explore the role of methoxysilyl groups in organosilanes during the formation of hierarchical structure. The prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N2 adsorption-desorption, FT-IR, UV-vis and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The characterization results showed that the use of TPOAC and DPOAC would generate short-range ordered mesopores and irregular mesopores, respectively. Hierarchical ZSM-5 zeolite nanorods with worm-like intracrystalline mesopores could be obtained by adjusting the amount of silicon source. The lack of methoxysilyl groups in OTAC however could lead to phase separation problems. Furthermore, the hierarchical Fe-ZSM-5 zeolite with short-range ordered mesoporosity showed enhanced catalytic activity and stability for the hydroxylation of phenol at room temperature.

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New Zn(II) coordination polymers constructed from amino-alcohols and aromatic dicarboxylic acids: Synthesis, structure, photocatalytic properties, and solid-state conversion to ZnO

Four new coordination polymers have been obtained solvothermally from the reactions of Zn(NO3)2·6H2O with 1,2-, 1,3-, or 1,4-benzedicarboxylic acids in the presence of various amino-alcohols: 1 [Zn2(Htea)2(1,2-bdc)] (1), 1 [Zn(H3tris)(1,3-bdc)(CH3OH)] (2), 3 [Zn5(Htea)2(1,3-bdc)3(H2O)]·2.6H2O (3), and 3 [Zn3(H2dea)2(1,4-bdc)3] (4) (H3tea = triethanolamine, H3tris = tris(hydroxymethyl)aminomethane, H2dea = diethanolamine, 1,2-H2bdc =1,2-benzenedicarboxylic acid, 1,3-H2bdc =1,3-benzenedicarboxylic acid, and 1,4-H2bdc =1,4-benzenedicarboxylic acid). Their crystal structures, thermogravimetric analyses, solid-state transformation to ZnO and characterization of the resultant zinc oxide particles are reported. Compounds 1 and 2 show three-dimensional (3D) supramolecular architectures, generated from the interconnection of the zigzag (in 1) and respectively the linear (in 2) chains through hydrogen bonding interactions. The crystal structure of 3 revealed the presence of five different types of zinc atoms that are successively linked through carboxilato or alkoxo bridges in a helicoidal chain running along the crystallographic a axis. Both right-handed (P) and left-handed (M) helices are present in the crystal, and they are alternately interconnected by pairs of isophthalato bridges, resulting in channels of hexagonal shape, filled with water molecules. Compound 4 has a 3D structure in which linear centrosymmetric {Zn3(H2dea)2}6+ nodes are joined by terephthalate bridges. Owing to its porous network, compound 3 was tested in two selective reactions: photooxidation of phenol to hydroquinone and aerobic photooxidative condensation of benzylamine to N-benzylidenebenzylamine.

Synthesis and characterization of bio-inspired diiron complexes and their catalytic activity for direct hydroxylation of aromatic compounds

Three [FeFe]-hydrogenase model complexes [(μ-dmedt){Fe(CO)3}2] [1; dmedt = SCH(CH3)CH(CH3)S], [(μ-dmedt){Fe(CO)3}{Fe (CO)2PPh3}] (1-PPh3), and [(μ-dmest){Fe(CO)3}2] [1-O; dmest = SCH(CH3)CH(CH3)S(O)], 1-O were synthesized and characterized. These model complexes, which are generally used as the functional biomimics of the hydrogen-producing dinuclear active site in [FeFe]-hydrogenase, were used as efficient catalysts for the selective hydroxylation of aromatic compounds to phenols under mild conditions. Because both the dithiolato-sulfur site and the Fe-Fe bond in the model complexes were possible active oxidation sites, DFT calculations were used to investigate the oxygenated products, that is, the S-oxygenated products or the Fe-oxygenated forms of the model complexes, which may be involved in the catalytic cycle. The experimental and computational results indicate that the thermodynamically favored Fe-oxygenated intermediates dominate the hydroxylation of the aromatic compounds. A possible mechanism for the hydroxylation is also proposed. Three FeI-FeI organometallic complexes were synthesized and used as highly selective catalysts for the direct hydroxylation of aromatic compounds to phenols, forming FeII-μ-O-FeII intermediates as the active oxygen-transfer species.

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Reductions by aquatitanium(II)

Solutions of titanium(II), prepared by dissolving titanium wire in mixtures of hydrofluoric and triflic acids, reduce quinones, nitrosodisulfonate anion, and complexes of cobalt(III). When the oxidant is taken in excess, these reactions yield Ti(IV), whereas with excess reductant, the principal product is Ti(III). These reactions are compared with those by Ti(III). Despite differences in rate laws, it is clear that rate ratios for the two reductants (k TiII/kTiIII) fall well below 10 4, the minimum selectivity corresponding to estimated differences in formal potentials, and in some instances, Ti(II), the stronger reductant, reacts more slowly. For both Ti(III) and Ti(II), reductions within the series [Co(NH3)5X]2+ (where X = F, Cl, Br, and I), the fluoro complex reacts much more rapidly than its congeners, and the bromo and iodo complexes are slowest, an order similar to that for Eu2+ reductions, but opposite to that for Cr(II) and Cu(I). The [Co(NH 3)5Br]2+ reaction with excess Ti(II) proceeds at rates very nearly independent of [oxidant] during the first 80-90% reaction, implying that initiation occurs via unimolecular conversion of Ti(II) to an activated cationic reducing species, in the same manner as the earlier described reduction of I3- by Ge(II) in aqueous HCl. The Royal Society of Chemistry 2005.

Evidence for single electron transfer (SET) pathway in the reaction of primary alkylcadmium reagents with p-benzoquinone

The reaction of primary alkylcadmium reagents with p-benzoquinone at various conditions was studied. On the basis of our results, reaction proceeds through a SET mechanism that forms loose and tight intermediates, which produce quinole (1) and substituted hydroquinone (2). In both cases, hydroquinone (3) is obtained in different yields.

Briggs-Rauscher reaction with 1,4-cyclohexanedione substrate

A new organic substrate has been used to promote oscillations under batch conditions in the Briggs-Rauscher oscillating system. The new substrate, 1,4-cyclohexanedione (CHD), reacts with aqueous iodine via an enol mechanism. We discuss the effect of the initial concentrations, the temperature and chemical perturbations. In a definite range of concentrations long-lived oscillations with two significantly different frequency periods were observed. The low frequency parts are temperature-dependent while the high frequency oscillations do not show temperature dependence. The inhibitory effects of 1,4-hydroquinone and 1,4-benzoquinone on the oscillations and the kinetics of some important component reactions were studied to develop a model for the simulation of the observed oscillations. by Oldenbourg Wissenschaftsverlag.

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Activation of Water with Anionic Platinum Carbonyl Clusters

Rate parameters have been determined for the oxidation of water to oxygen by (2-).The cluster anion is found to catalyse the conversion of p-benzoquinone to benzene-1,4-diol with water or hydrogen.U.v.-visible and i.r.spectroscopy suggest the

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Effects of Pressure on the Photoreduction of p-Benzoquinone in Normal and Reversed Micellar Sysytems

The photoreduction of p-benzoquinone (p-BQ) in normal and reversed micellar systems has been studied kinetically under high pressures up to 150 MPa.Anionic sodium dodecyl sulphate (SDS) micelles accelerated the reaction, while cationic hexadecyltrimethyla

Ultrasound-promoted rapid and efficient iodination of aromatic and heteroaromatic compounds in the presence of iodine and hydrogen peroxide in water

A rapid and efficient ultrasound-promoted protocol for iodination of aromatic and heteroaromatic compounds, using molecular iodine in the presence of aqueous hydrogen peroxide in water without any cosolvent, has produced versatile iodinated organic molecules with potential application in organic synthesis and medicine in short reaction times and good to excellent yields. Copyright

Benzene-free synthesis of hydroquinone

All current routes for the synthesis of hydroquinone utilize benzene as the starting material. An alternate route to hydroquinone has now been elaborated from glucose. While benzene is a volatile carcinogen derived from nonrenewable fossil fuel feedstocks, glucose is nonvolatile, nontoxic, and derived from renewable plant polysacharrides. Glucose is first converted into quinic acid using microbial catalysis. Quinic acid is then chemically converted into hydroquinone. Under fermentor-controlled conditions, Escherichia coli QP1.1/pKD12.138 synthesizes 49 g/L of quinic acid from glucose in 20% (mol/mol) yield. Oxidative decarboxylation of quinic acid in clarified, decolorized, ammonium ion-free fermentation broth with NaOCl and subsequent dehydration of the intermediate 3(R),5(R)-trihydroxycyclohexanone afforded purified hydroquinone in 87% yield. Halide-free, oxidative decarboxylation of quinic acid in fermentation broth with stoichiometric quantities of (NH4)2Ce(SO4)3 and V2O5 afforded hydroquinone in 91% and 85% yield, respectively. Conditions suitable for oxidative decarboxylation of quinic acid with catalytic amounts of metal oxidant were also identified. Ag3PO4 at 2 mol % relative to quinic acid in fermentation broth catalyzed the formation of hydroquinone in 74% yield with K2S2O8 serving as the cooxidant. Beyond establishing a fundamentally new route to an important chemical building block, oxidation of microbe-synthesized quinic acid provides an example of how the toxicity of aromatics toward microbes can be circumvented by interfacing chemical catalysis with biocatalysis.

Biomass-Based and Oxidant-Free Preparation of Hydroquinone from Quinic Acid

A biomass-based route to the preparation of hydroquinone starting from the renewable starting material quinic acid is described. Amberlyst-15 in the dry form promoted the one-step formation of hydroquinone from quinic acid in toluene without any oxidants or metal catalysts in 72 % yield. Several acidic polymer-based resins and organic acids as promoters as well as a variety of reaction conditions were screened including temperature, concentration and low- and high-boiling-point solvents. A 1:4 (w/w) ratio of quinic acid/Amberlyst-15 was determined to be optimal to promote hydroquinone formation with only traces of a dimeric side-product. A mechanism has been proposed based on the decarbonylation of protonated quino-1,5-lactone that is supported by experimental and computational calculation data.

Kinetics of phenol oxidation with iron-manganese concretions

Kinetics of oxidation of phenols on the iron-manganese concretions in the temperature range 293-353 K at pH 5.5±0.5 was studied. Reaction of oxidation on the iron-manganese concretions has the second order by phenol. It is characterized by low activation energy, 17.5 kJ mol-1, due to the catalytic action of iron(III) oxide. Lower rate of oxidation of phenols on the iron-manganese concretions is observed as compared to oxidation on the pyrolusite surface. It occurs because of the decrease in MnO2 concentration in the iron-manganese concretions.

The 1,4-cyclohexanedione-bromate-acid oscillatory system. 3. Detailed mechanism

1,4-Cyclohexanedione (CHD) in its reaction with acidic bromate undergoes aromatization and one of the main resulting products 1,4-dihydroxybenzene (H2Q) is further oxidized and brominated to 1,4-benzoquinone and bromoorganics. The kinetics of H2Q formation, of the reaction of CHD and Br2. as well as of the reaction between H2Q and bromate ion, were followed spectrophotometrically. The latter reaction exhibited Landolt (clock)-type dynamics. On the basis of our earlier analytical and present kinetic investigations, a detailed mechanistic model has been suggested that could well simulate the temporal oscillations of the title system. H2Q plays an essential role in the mechanism and is responsible for the unusual behavior (200-300 oscillations) of this chemical oscillator. We pointed to the relation that may exist between the CHD-bromate-acid system and those reported as oscillatory Landolt-type reactions [e.g., IO3- - SO32- - Fe(CN)64-].

Analysis of Products from Reactions of Chemisorbed Monolayers at Smooth Platinum Electrodes: Electrochemical Hydrodesulfurization of Thiophenol Derivatives

The product mixtures from electrochemical hydrodesulfurization of selected thiophenolic compounds chemisorbed through the -SH moiety at smooth Pt electrodes in molar acid have been analyzed quantitatively by using thin-layer electrochemical methods in conjunction with capillary gas chromatography and liquid chromatography.The following compounds were studied: pentafluorothiophenol (PFT), mercaptohydroquinone (MHQ), and 2-mercaptobenzoic acid (MBA).A comparatively high area, large-volume preparative thin-layer electrode (TLE) was constructed to facilitate sample analysis.The results obtained from TLE, GC, and HPLC analysis were in good agreement.The extent of hydrodesulfurization (defined here as simple cleavage of the C-S bond without impairment of the aromatic functionality) depended on the nature of the pendant aromatic ring, decreasing in the order PFT (100percent) >> MHQ (50percent) >>MBA (15percent).Only one desulfurization product was observed for MHQ and MBA; the absence of other products was probably because ring hydrogenation (to form alkyl-type groups) competed with simple desulfurization, and detachment of the alkyl moieties from the -SH anchor occured with greater difficulty than that of the aromatic group.

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A PHENOL ALLOSIDE FROM VIBURNUM WRIGHTII

A new phenol alloside, p-hydroxyphenyl β-D-alloside, has been isolated from the leaves of Viburnum wrightii in addition to several known compounds.The structures were elucidated by spectroscopic and chemical methods. - Keywords: Viburnum wrightii; Caprifoliaceae; phenol alloside.

Photocatalytic removal of benzene over Ti3C2T: XMXene and TiO2-MXene composite materials under solar and NIR irradiation

MXenes, a family of two-dimensional (2D) transition metal carbides, nitrides and carbonitrides based on earth-abundant constituents, are prospective candidates for energy conversion applications, including photocatalysis. While the activity of individual MXenes towards various photocatalytic processes is still debatable, these materials were proved to be excellent co-catalysts, accelerating the charge separation and suppressing the exciton recombination. Titanium-containing MXenes are well compatible with the classical TiO2 photocatalyst. The TiO2 component can be directly grown on MXene sheets by in situ oxidation, representing a mainstream processing approach for such composites. In this study, an essentially different approach has been implemented: a series of TiO2-MXene composite materials with controlled composition and both reference end members were prepared, involving two different strategies for mixing sol-gel-derived TiO2 nanopowder with the Ti3C2Tx component, which was obtained by HF etching of self-propagating high-temperature synthesis products containing modified MAX phase Ti3C2Alz (z > 1) with nominal aluminium excess. The prospects of such composites for the degradation of organic pollutants under simulated solar light, using benzene as a model system, were demonstrated and analysed in combination with their structural, microstructural and optical properties. A notable photocatalytic activity of bare MXene under near infrared light was discovered, suggesting further prospects for light-to-energy harvesting spanning from UV-A to NIR and applications in biomedical imaging and sensors.

Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water

A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.

Highly efficient titanosilicate catalyst Ti-MCM-68 prepared using a liquid-phase titanium source for the phenol oxidation

A highly efficient Ti-MCM-68 catalyst for phenol oxidation with H2O2 was prepared by a mild liquid-phase treatment for the first time. The key preparation procedures to excellent catalytic activity and high para-selectivity were the use of aqueous solutions of the Ti source and calcination at 650 °C prior to catalytic use.