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A hydroxyl is a chemical functional group containing one oxygen atom connected by a covalent bonding to one hydrogen atom. It is sometimes called the alcohol functional group because when bonded to carbon in a molecule that otherwise contains only hydrogen and carbon the hydroxy (not hydroxyl) group defines the molecule as an alcohol, resulting in a name ending in -ol. A hydroxyl group bonded covalently to the carbon of a carbonyl group (C=O) produces a carboxyl group (C(O)OH) that is the defining group of a carboxylic acid. When the −OH group participates in an ionic bond, the () anion is called the "hydroxide" ion. ==Hydroxy group== According to IUPAC rules the term hydroxyl refers to the radical OH only, while the functional group −OH is called hydroxy group.〔(【引用サイトリンク】url=http://goldbook.iupac.org/A00204.html )〕 The oxygen atom in the hydroxy group is much more electronegative than the hydrogen, so that the electrons are closer to the oxygen atom. Similar to water, compounds containing the hydroxy group are capable of forming hydrogen bonds. Primary alcohols are miscible with water. In complex compounds, the portion of the molecule containing the hydroxy group is hydrophilic. The hydroxy group appears throughout organic chemical structure and biochemical structure. It appears covalently bonded to carbon in sugars. The hydroxy group appears on the second carbon atom of the hydroxy amino acids serine and threonine. It appears on the phenol side chain of tyrosine. The capacity of the hydroxy group to form hydrogen bonds imparts water solubility and internal structural stability to proteins that include these amino acids. Hydroxy groups participate in the dehydration reactions that link simple biological molecules into long chains. The joining of a fatty acid to glycerol to form a triacylglycerol removes the −OH from the carboxy end of the fatty acid. The joining of two aldehyde sugars to form a disaccharide removes the −OH from the carboxy group at the aldehyde end of one sugar. The creation of a peptide bond to link two amino acids to make a protein removes the −OH from the carboxy group of one amino acid. 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「Hydroxyl」の詳細全文を読む スポンサード リンク
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