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A carboxylic acid is an organic compound that contains a carboxyl group (C(O)OH). The general formula of a carboxylic acid is R−C(O)OH with R referring to the rest of the (possibly quite large) molecule. Carboxylic acids occur widely and include the amino acids and acetic acid (as vinegar). Salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base forms a carboxylate anion. Carboxylate ions are resonance-stabilized, and this increased stability makes carboxylic acids more acidic than alcohols. Carboxylic acids can be seen as reduced or alkylated forms of the Lewis acid carbon dioxide; under some circumstances they can be decarboxylated to yield carbon dioxide. ==Example carboxylic acids and nomenclature== Carboxylic acids are commonly named as indicated in the table below. Although rarely used, IUPAC-recommended names also exist. For example, butyric acid (C3H7CO2H) is, according to IUPAC guidelines, also known as butanoic acid.〔(Recommendations 1979 ). Organic Chemistry IUPAC Nomenclature. Rules C-4 Carboxylic Acids and Their Derivatives.〕 To more easily understand much of the below discussion of reactions involving carboxylic acids it can be helpful to notice that the carboxyl group itself is a "hydroxylated carbonyl group" meaning that two of the carbon atom's four bonds are to an oxygen atom, the carbon atom's third bond is to a second oxygen atom (whose other bond is to a hydrogen atom), and the carbon atom's fourth bond attaches to R. (carbon atom double bonded to an oxygen atom is a carbonyl group and two of the carbon atom's bonds remain available for bonding. A hydrogen atom bonded to an oxygen atom is a hydroxyl group with the oxygen atom's second bond available for bonding. ) The carboxylate anion R-COO− is usually named with the suffix ''ate'', so acetic acid, for example, becomes acetate ion. In IUPAC nomenclature, carboxylic acids have an ''oic acid'' suffix (e.g., octadecanoic acid). For trivial names, the suffix is usually ''ic acid'' (e.g., stearic 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「carboxylic acid」の詳細全文を読む スポンサード リンク
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