Phloroglucinol

Phloroglucinol is an organic compound with the formula C6H3(OH)3. It is a colorless solid. It is used in the synthesis of pharmaceuticals and explosives. Phloroglucinol is one of three isomeric benzenetriols. The other two isomers are hydroxyquinol (1,2,4-benzenetriol) and pyrogallol (1,2,3-benzenetriol). Phloroglucinol, and its benzenetriol isomers, are still defined as "phenols" according to the IUPAC official nomenclature rules of chemical compounds. Many such monophenolics are often termed polyphenols. In 1855, phloroglucinol was first prepared from phloretin by the Austrian chemist Heinrich Hlasiwetz (1825–1875). A modern synthesis of phloroglucinol involves hydrolysis of benzene-1,3,5-triamine and its derivatives. Representative is the following route from trinitrobenzene. The synthesis is noteworthy because ordinary aniline derivatives are unreactive toward hydroxide. Because the triaminobenzene also exists as its imine tautomer, it is susceptible to hydrolysis. Phloroglucinol is a weak triprotic acid. The first two pKa's are 8.5 and 8.9. As an enol, phloroglucinol in principle exists in equilibrium with keto tautomers. Evidence for this equilibrium is provided by the formation of the oxime: C6H3(OH)3 + 3 NH2OH → (CH2)3(C=NOH)3 + 3 H2O But it behaves also like a benzenetriol as the three hydroxyl groups can be methylated to give 1,3,5-trimethoxybenzene. For the neutral compound, the keto tautomers are undetectable spectroscopically. Upon deprotonation, the keto tautomer predominates. From water, phloroglucinol crystallizes as the dihydrate, which has a melting point of 116–117 °C, but the anhydrous form melts at a much higher temperature, at 218–220 °C. It does not boil intact, but it does sublime. The Hoesch reaction allows the synthesis of 1-(2,4,6-Trihydroxyphenyl)ethanone from phloroglucinol. Leptospermone can be synthesized from phloroglucinol by a reaction with isovaleroylnitrile in the presence of a zinc chloride catalyst. Pentacarbon dioxide, described in 1988 by Günter Maier and others, can be obtained by pyrolysis of 1,3,5-cyclohexanetrione (phloroglucin).

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Naturally occurring phenols

In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research.

Polyphenol

Polyphenols (ˌpɒliˈfiːnoʊl,_-nɒl) are a large family of naturally occurring phenols. They are abundant in plants and structurally diverse. Polyphenols include flavonoids, tannic acid, and ellagitannin, some of which have been used historically as dyes and for tanning garments. The name derives from the Ancient Greek word πολύς (polus, meaning "many, much") and the word ‘phenol’ which refers to a chemical structure formed by attachment of an aromatic benzenoid (phenyl) ring to a hydroxyl (-OH) group as is found in alcohols (hence the -ol suffix).

Tannin

Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term tannin (from Anglo-Norman tanner, from Medieval Latin tannāre, from tannum, oak bark) refers to the use of oak and other bark in tanning animal hides into leather. By extension, the term tannin is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with various macromolecules.

Fractionation of lignocellulosic biomass to produce uncondensed aldehyde-stabilized lignin

Jeremy Luterbacher, Masoud Talebi Amiri, Ydna Marie Questell-Santiago, Graham Reid Dick

Lignin is one of the most promising sources of renewable aromatic hydrocarbons. Current methods for its extraction from lignocellulosic biomass—which include the kraft, sulfite, and organosolv processes—result in the rapid formation of carbon–carbon bonds, ...

2019

Formaldehyde stabilization facilitates lignin monomer production during biomass depolymerization

Yiming Li, Jeremy Luterbacher, Masoud Talebi Amiri, Florent Emmanuel Héroguel, Ydna Marie Questell-Santiago, Li Shuai

Practical, high-yield lignin depolymerization methods could greatly increase biorefinery productivity and profitability. However, development of these methods is limited by the presence of interunit carbon-carbon bonds within native lignin, and further by ...

American Association for the Advancement of Science2016

Surface Functionalisation of Alumina Ceramic Foams with Organic Ligands

Sandrine Gerber, Vincent Laporte, Pascal Miéville, Françoise Borcard, Marc Anthony Caporini

Different anchoring groups have been studied with the aim of covalently binding organic linkers to the surface of alumina ceramic foams. The results suggested that a higher degree of functionalisation was achieved with a pyrogallol derivative - as compared ...

2012