Tetrahydroxy-1,4-benzoquinone
Encyclopedia
Tetrahydroxy-1,4-benzoquinone, also called tetrahydroxy-p-benzoquinone, tetrahydoxybenzoquinone, or tetrahydroxyquinone (THBQ, THQ), is an organic compound
with formula C6O2(OH)4. Its molecular structure consists of a cyclohexadiene
ring with four hydroxyl
groups and two ketone
groups in opposite (para) positions.
The compound gives a light red solution in water, and crystallizes as the glistening bluish-black (but non-conducting) dihydrate
C6O2(OH)4·2H2O.
The compound can be synthesized from glyoxal
or from myo-inositol (phytic acid), a natural compound widely present in plants. THBQ forms an adduct
with 4,4'-bipyridine
in the 2:3 ratio.
s, THBQ is acid
ic and easily loses the four H+
ions from the hydroxyl
groups, yielding anions such as C6H2O62− and C6O64−. The latter is symmetric and aromatic, as the double bonds and negative charges are evenly distributed over the six CO groups.
The calcium
salt Ca2C6O6 is the dark purple pigment produced from inositol by Chromohalobacter beijerinckii
in the fermentation of salt bean
s, already noted by T. Hof in 1935.
The dark purple and insoluble dipotassium
salt K2C6H2O6 was prepared by Preisler and Berger in 1942, by oxidizing inositol
with nitric acid
and reacting the result with potassium carbonate
in the presence of oxygen. Reaction of this salt with hydrochloric acid
affords THBQ in good yield.
The black tetrapotassium salt K4C6O6 was prepared by West
and Niu in 1962, by reacting THBQ with potassium methoxide
in methanol
. The salt is diamagnetic and the infrared spectrum suggests that the C-C and C-O distances are all equal, with the ring slightly distorted in the "chair" conformation. Partial oxidation of K4C6O6 affords a green strongly paramagnetic solid, conjectured to be (K+)3 C6O63−, and complete oxidation yields potassium rhodizonate
(K+)2 C6O62−.
The greenish-black sodium
salt Na4C6O6 was described by Fatiadi
and Sanger in 1962.
The dark-violet lithium
salt Li4C6O6 has been proposed as an electrode material for batteries as it can be oxidized to the rhodizonate Li2C6O6 and reduced to the hexahydroxybenzene
salt Li6C6O6. In the absence of oxygen, Li4C6O6 is stable to about 450°C and then decomposes leaving a residue of carbonate
Li2CO3. Indeed, the rhodizonate appears to disproportionate
at about 400°C into Li4C6O6 and cyclohexanehexone
C6O6 that promptly decomposes to carbon monoxide
, carbon dioxide
, and carbon. Li2C6O6 forms a hydrate
Li4C6O6·2H2O that loses its water at about 250°C.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with formula C6O2(OH)4. Its molecular structure consists of a cyclohexadiene
Cyclohexadiene
-See also:* Benzene or its theoretical isomer 1,3,5-Cyclohexatriene* Cyclohexene...
ring with four hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
groups and two ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
groups in opposite (para) positions.
The compound gives a light red solution in water, and crystallizes as the glistening bluish-black (but non-conducting) dihydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
C6O2(OH)4·2H2O.
The compound can be synthesized from glyoxal
Glyoxal
Glyoxal is an organic compound with the formula OCHCHO. This yellow colored liquid is the smallest dialdehyde . Its tautomer acetylenediol is unstable.-Production:...
or from myo-inositol (phytic acid), a natural compound widely present in plants. THBQ forms an adduct
Adduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...
with 4,4'-bipyridine
4,4'-Bipyridine
4,4'-Bipyridine is a bipyridine which is mainly used as a precursor to N,N'-dimethyl-4,4'-bipyridinium [2]2+, known as paraquat. This species is electroactive, and its toxicity arises from the ability of this dication to interrupt biological electron transfer...
in the 2:3 ratio.
Salts of THBQ
Like most phenolPhenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
s, THBQ is acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic and easily loses the four H+
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
ions from the hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
groups, yielding anions such as C6H2O62− and C6O64−. The latter is symmetric and aromatic, as the double bonds and negative charges are evenly distributed over the six CO groups.
The calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
salt Ca2C6O6 is the dark purple pigment produced from inositol by Chromohalobacter beijerinckii
Chromohalobacter beijerinckii
Chromohalobacter beijerinckii is a motile, rod-like, salt-loving, Gram-negative soil bacterium, 0.4–0.6 μm by 1.8–2.5 μm.The bacterium was isolated in 1935 by T. Hof from fermented salted beans preserved in brine. Hof named it Pseudomonas beijerinckii and identified it as the organism responsible...
in the fermentation of salt bean
Bean
Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....
s, already noted by T. Hof in 1935.
The dark purple and insoluble dipotassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
salt K2C6H2O6 was prepared by Preisler and Berger in 1942, by oxidizing inositol
Inositol
Inositol or cyclohexane-1,2,3,4,5,6-hexol is a chemical compound with formula 6126 or 6, a sixfold alcohol of cyclohexane. It exists in nine possible stereoisomers, of which the most prominent form, widely occurring in nature, is cis-1,2,3,5-trans-4,6-cyclohexanehexol, or myo-inositol...
with nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
and reacting the result with potassium carbonate
Potassium carbonate
Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
in the presence of oxygen. Reaction of this salt with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
affords THBQ in good yield.
The black tetrapotassium salt K4C6O6 was prepared by West
Robert West
Robert C. West is E. G. Rochow Professor of Chemistry Emeritus at the University of Wisconsin–Madison; Director of the Organosilicon Research Center, University of Wisconsin–Madison 1999–present; President, Silatronix, Inc...
and Niu in 1962, by reacting THBQ with potassium methoxide
Methoxide
Methoxides are organic salts and the simplest alkoxides. Sodium methoxide and potassium hydroxide have widespread use, though other variants such as lithium hydroxide, rubidium methoxide, caesium methoxide, and francium methoxide exist as well.- Methoxide ion :In organic chemistry, the methoxide...
in methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
. The salt is diamagnetic and the infrared spectrum suggests that the C-C and C-O distances are all equal, with the ring slightly distorted in the "chair" conformation. Partial oxidation of K4C6O6 affords a green strongly paramagnetic solid, conjectured to be (K+)3 C6O63−, and complete oxidation yields potassium rhodizonate
Rhodizonic acid
Rhodizonic acid is a chemical compound with formula C6H2O6 or 42. It can be seen as a two-fold alcohol and four-fold ketone of cyclohexene, more precisely 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone....
(K+)2 C6O62−.
The greenish-black sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
salt Na4C6O6 was described by Fatiadi
Alexander J. Fatiadi
Alexander J. Fatiadi is a chemist.He obtained his masters from the George Washington University, Washington DC . He has worked at the National Bureau of Standards.-Selected publications:...
and Sanger in 1962.
The dark-violet lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
salt Li4C6O6 has been proposed as an electrode material for batteries as it can be oxidized to the rhodizonate Li2C6O6 and reduced to the hexahydroxybenzene
Benzenehexol
Benzenehexol, also called hexahydroxybenzene, is an organic compound with formula C6H6O6 or C66. It is a six-fold alcohol of benzene. The product is also erroneously called hexaphenol, but this name has been used also for other substances....
salt Li6C6O6. In the absence of oxygen, Li4C6O6 is stable to about 450°C and then decomposes leaving a residue of carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
Li2CO3. Indeed, the rhodizonate appears to disproportionate
Disproportionation
Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....
at about 400°C into Li4C6O6 and cyclohexanehexone
Cyclohexanehexone
Cyclohexanehexone, also known as hexaketocyclohexane and triquinoyl, is a organic compound with formula C6O6, the sixfold ketone of cyclohexane...
C6O6 that promptly decomposes to carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
, and carbon. Li2C6O6 forms a hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
Li4C6O6·2H2O that loses its water at about 250°C.