syringol
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Syringol is the
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. The ...
with the formula HO(CH3O)2C6H3. The molecule is a phenol, with
methoxy In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula . On a benzene ring, the Hammett equation classifies a methoxy substituent at the ''para'' position a ...
groups in the flanking (2 and 6) positions. It is the symmetrically dimethylated derivative of
pyrogallol Pyrogallol is an organic compound with the formula C6H3(OH)3. It is a water-soluble, white solid although samples are typically brownish because of its sensitivity toward oxygen. It is one of three isomers of benzenetriols. Production and react ...
. It is a colorless solid, although typical samples are brown owing to air-oxidized impurities. Together with
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 ...
, syringol and its derivatives are produced by the
pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...
of
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity ...
. Specifically, syringol is derived from the
thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is req ...
of the
sinapyl alcohol Sinapyl alcohol is an organic compound structurally related to cinnamic acid. It is biosynthetized via the phenylpropanoid biochemical pathway, its immediate precursor being sinapaldehyde. This phytochemical is one of the monolignols, which are ...
component. As such, syringol is an important component of
wood smoke Smoke is a suspension of airborne particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-produc ...
.


Syringyl/guaiacyl ratio

Lignin, comprising a major fraction of biomass, is sometimes classified according to the syringyl component. Pyrolysis of lignin derived from sinapyl alcohol affords syringol. The conversion involves replacement of the propenyl alcohol substituent of the sinapyl alcohol by hydrogen. A high syringyl (or S) content is indicative of lignin from
angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s. In contrast, pyrolysis of lignin from
gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, Î³Ï…Î¼Î½ÏŒÏ ...
s gives more
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 ...
, resulting from conversion of
coniferyl alcohol Coniferyl alcohol is an organic compound with the formula HO(CH3O)C6H3CH=CHCH2OH. A colourless or white solid, it is one of the monolignols, produced via the phenylpropanoid biochemical pathway. When copolymerized with related aromatic compounds, ...
. These lignins have a high guaiacyl (or G) content.


Food preparation

In preparation of food by
smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...
, syringol is the main chemical responsible for the smoky
aroma An odor (American English) or odour ( Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their se ...
, while guaiacol contributes mainly to
taste The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
. Artificial liquid or solid smoke flavorings also contain these chemicals, on average composing 13.73% and 13.42% of those products by mass respectively.


Chemical feedstock

Pyrolysis oil Pyrolysis oil, sometimes also known as bio-crude or bio-oil, is a synthetic fuel under investigation as substitute for petroleum. It is obtained by heating dried biomass without oxygen in a reactor at a temperature of about with subsequent coo ...
, a
biofuel Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
derived from woody biomass, can be optimized to yield syringol as a byproduct, potentially competing with petroleum-derived
phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it req ...
s. Some studies indicate that syringol can substitute for
phenol formaldehyde resin Phenol formaldehyde resins (PF) or phenolic resins (also infrequently called phenoplasts) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commerc ...
, a commonly used, water resistant
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
for
plywood Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured ...
.


See also

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Phenolic content in wine The phenolic content in wine refers to the phenolic compounds—natural phenol and polyphenols—in wine, which include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include ...
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Syringaldehyde Syringaldehyde is an organic compound that occurs in trace amounts widely in nature. Some species of insects use syringaldehyde in their chemical communication systems. ''Scolytus multistriatus'' uses it as a signal to find a host tree during ovip ...
*
Syringic acid Syringic acid is a naturally occurring phenolic compound and dimethoxybenzene that is commonly found as a plant metabolite. Natural occurrence Syringic acid can be found in several plants including ''Ardisia elliptica'' and '' Schumannianthus d ...
*
Acetosyringone Acetosyringone is a phenolic natural product and a chemical compound related to acetophenone and 2,6-dimethoxyphenol. It was first described in relation to lignan/phenylpropanoid-type phytochemicals, with isolation from a variety of plant source ...
*
Sinapaldehyde Sinapaldehyde is an organic compound with the formula HO(CH3O)2C6H2CH=CHCHO. It is a derivative of cinnamaldehyde, featuring one hydroxy group and two methoxy groups as substituents. It is an intermediate in the formation of sinapyl alcohol, a ...
*
Sinapinic acid Sinapinic acid, or sinapic acid (Sinapine - Origin: L. Sinapi, sinapis, mustard, Gr., cf. F. Sinapine.), is a small naturally occurring hydroxycinnamic acid. It is a member of the phenylpropanoid family. It is a commonly used matrix in MALDI mass ...
*
Sinapine Sinapine is an alkaloidal amine found in some seeds, particularly oil seeds of plants in the family Brassicaceae. It is the choline ester of sinapic acid. Sinapine was discovered by Etienne Ossian Henry in 1825. Occurrence Sinapine typically ...
*
Canolol Canolol is a phenolic compound found in crude canola oil. It is produced by decarboxylation of sinapic acid during canola seed roasting.Isolation and Identification of a Potent Radical Scavenger (Canolol) from Roasted High Erucic Mustard Seed Oil ...


References

{{reflist O-methylated natural phenols