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In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group (—OH) bonded directly to an aromatic hydrocarbon group. The simplest of the class is phenol, which is also called carbolic acid . Phenolic compounds are classified as simple phenols or polyphenols based on the number of phenol units in the molecule. Synonyms are arenols〔IUPAC〕 or aryl alcohols.〔UniProt〕 Phenolic compounds are synthesized industrially; they also are produced by plants and microorganisms, with variation between and within species. Although similar to alcohols, phenols have unique properties and are not classified as alcohols (since the hydroxyl group is not bonded to a ''saturated'' carbon atom). They have higher acidities due to the aromatic ring's tight coupling with the oxygen and a relatively loose bond between the oxygen and hydrogen. The acidity of the hydroxyl group in phenols is commonly intermediate between that of aliphatic alcohols and carboxylic acids (their pKa is usually between 10 and 12). Loss of a positive hydrogen ion (H+) from the hydroxyl group of a phenol forms a corresponding negative phenolate ion or phenoxide ion, and the corresponding salts are called phenolates or phenoxides, although the term aryloxides is preferred according to the (IUPAC Gold Book ). Phenols can have two or more hydroxy groups bonded to the aromatic ring(s) in the same molecule. The simplest examples are the three benzenediols, each having two hydroxy groups on a benzene ring. Organisms that synthesize phenolic compounds do so 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.〔〔〔Robert E.C. Wildman, Editor. (Handbook of Nutraceuticals and Functional Foods, Second Edition ). CRC Press; 2 edition, 2006. ISBN 0849364094〕 Some phenols are germicidal and are used in formulating disinfectants. Others possess estrogenic or endocrine disrupting activity. == Classification == There are various classification schemes.〔Wilfred Vermerris and Ralph Nicholson. (Phenolic Compound Biochemistry ) Springer, 2008〕 A commonly used scheme is based on the number of carbons and was devised by Jeffrey Harborne and Simmonds in 1964 and published in 1980:〔 Not in this Harborne classification are the C6-C7-C6 diarylheptanoids. They can also be classified on the basis of their number of phenol groups. They can therefore be called ''simple phenols'' or ''monophenols'', with only one phenolic group, or ''di-'' (''bi-''), ''tri-'' and ''oligophenols'', with two, three or several phenolic groups respectively. The largest and best studied natural phenols are the flavonoids, which include several thousand compounds, among them the flavonols, flavones, flavan-3ol (''catechins''), flavanones, anthocyanidins and isoflavonoids. The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol. For example, ellagic acid is a dimer of gallic acid and forms the class of ellagitannins, or a catechin and a gallocatechin can combine to form the red compound theaflavin, a process that also results in the large class of brown thearubigins in tea. Two natural phenols from two different categories, for instance a flavonoid and a lignan, can combine to form a hybrid class like the flavonolignans. Nomenclature of polymers: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phenols」の詳細全文を読む スポンサード リンク
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