In
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...
, dihydroxybenzenes (benzenediols) are
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
s in which two
hydroxyl group
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...
s () are
substituted
A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. Substitution reactions ar ...
onto a
benzene ring
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atom ...
(). These
aromatic compound
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...
s are classed as
phenols
In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of one or more hydroxyl groups (— O H) bonded directly to an aromatic hydrocarbon group. The simplest is phenol, . Phenolic compounds are ...
. There are three
structural isomer
In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is another compound whose molecule has the same number of atoms of each element, but with logically distinct bonds between them. The term meta ...
s: 1,2-dihydroxybenzene (the ''ortho'' isomer) is commonly known as
catechol
Catechol ( or ), also known as pyrocatechol or 1,2-dihydroxybenzene, is a toxic organic compound with the molecular formula . It is the ''ortho'' isomer of the three isomeric benzenediols. This colorless compound occurs naturally in trace amoun ...
, 1,3-dihydroxybenzene (the ''meta'' isomer) is commonly known as
resorcinol
Resorcinol (or resorcin) is an organic compound with the formula C6H4(OH)2. It is one of three isomeric benzenediols, the 1,3-isomer (or '' meta''-isomer). Resorcinol crystallizes from benzene as colorless needles that are readily soluble in ...
, and 1,4-dihydroxybenzene (the ''para'' isomer) is commonly known as
hydroquinone
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. It has two hydroxyl groups bonded to a benzene ring in a ''pa ...
.
:
All three of these compounds are colorless to white granular
solid
Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structur ...
s at room
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
and
pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
, but upon exposure to oxygen they may darken. All three isomers have the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...
.
Similar to other phenols, the hydroxyl groups on the aromatic ring of a benzenediol are weakly
acidic
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...
. Each benzenediol can lose an from one of the hydroxyls to form a type of
phenolate
Phenolates (also called phenoxides) are anions, salts, and esters of phenols. They may be formed by reaction of phenols with strong base.
Properties
Alkali metal phenolates, such as sodium phenolate hydrolyze in aqueous solution to form basic s ...
ion.
The
Dakin oxidation
The Dakin oxidation (or Dakin reaction) is an organic redox reaction in which an '' ortho''- or '' para''-hydroxylated phenyl aldehyde ( 2-hydroxybenzaldehyde or 4-hydroxybenzaldehyde) or ketone reacts with hydrogen peroxide in base to form ...
is an organic
redox reaction
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
in which an ''ortho''- or ''para''-hydroxylated phenyl
aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl gro ...
() or
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double b ...
() reacts with
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3 ...
in base to form a benzenediol and a
carboxylate
In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge.
Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...
. Overall, the
carbonyl group
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
() is oxidized, and the hydrogen peroxide is reduced.
See also
*
Trihydroxybenzenes The trihydroxybenzenes (or benzenetriols) are organic compounds with the formula C6H3(OH)3. Also classified as polyphenols, they feature three hydroxyl groups substituted onto a benzene ring. They are white solids with modest solubility in water.
...
*
Tetrahydroxybenzenes Tetrahydroxybenzenes or Benzenetetrols are a group of Organic compound, organic compounds which are Hydroxy group, tetrahydroxy Derivative (chemistry), derivatives of benzene. Tetrahydroxybenzene comes in three Isomer, isomers:
*1,2,3,4-Tetrahydrox ...
*
Pentahydroxybenzene
Pentahydroxybenzene (C6H6O5) is a chemical compound whose structure consists of a benzene ring with five hydroxy groups (–OH) as substituent
A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a ...
*
Hexahydroxybenzene
Benzenehexol, also called hexahydroxybenzene, is an organic compound with formula or . It is a six-fold Phenols, phenol of benzene. The product is also called hexaphenol, but this name has been used also for other substances.
Benzenehexol is a c ...
*
Methylbenzenediol Methylbenzenediol, also known as dihydroxytoluene, may refer to:
* 3-Methylcatechol (3-methylbenzene-1,2-diol or 2,3-dihydroxytoluene)
* 4-Methylcatechol (4-methylbenzene-1,2-diol or 3,4-dihydroxytoluene)
* 2-methylbenzene-1,3-diol
* 4-methylbenzen ...
s (dihydroxytoluenes)
**
3-Methylcatechol
3-Methylcatechol is a chemical compound, a methylbenzenediol.
Metabolism
The enzyme 1,2-dihydroxy-6-methylcyclohexa-3,5-dienecarboxylate dehydrogenase uses 1,2-dihydroxy-6-methylcyclohexa-3,5-dienecarboxylate and NAD+ to produce 3-methylcatecho ...
(3-methylbenzene-1,2-diol)
**
4-Methylcatechol (4-methylbenzene-1,2-diol)
**
Orcinol
Orcinol is an organic compound with the formula CH3C6H3(OH)2. It occurs in many species of lichens including '' Roccella tinctoria'' and ''Lecanora''. Orcinol has been detected in the "toxic glue" of the ant species ''Camponotus saundersi''. It is ...
(5-methylbenzene-1,3-diol)
*
Methoxyphenols — can be derived from benzenediols by ''O''-
methylation
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These ...
**
Guaiacol
Guaiacol () is an organic compound with the formula C6H4(OH)(OCH3). It is a phenolic compound containing an methoxy functional group. Guaiacol appears as a viscous colorless oil, although aged or impure samples are often yellowish. It occurs wid ...
(2-methoxyphenol, ''O''-Methylcatechol)
**
Mequinol (4-Methoxyphenol)
*
Dimethoxybenzene
In organic chemistry, dimethoxybenzene is an organic compound which is derived from benzene () by substituting two methoxy groups (). Dimethoxybenzene comes in three structural isomers:
*1,2-Dimethoxybenzene (Veratrole)
* 1,3-Dimethoxybenzene
* 1 ...
s — can be derived from benzenediols by two rounds of ''O''-
methylation
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These ...
**
Veratrole
1,2-Dimethoxybenzene, commonly known as veratrole, is an organic compound with the formula CH( OCH). It is one of three isomers of dimethoxybenzene. It is a colorless liquid, with a pleasant odor and slight solubility in water. It is the dimethyl ...
(1,2-Dimethoxybenzene)
**
1,4-Dimethoxybenzene
References
{{chemistry index