Any organic compound with the general chemical formula 2015; COOH in which a carbon (C) atom is bonded to an oxygen (O) atom by a double bond to make a carbonyl group ( 2015; C 003D; O; see functional group ) and to a hydroxyl group ( 2015; OH) by a single bond (see bonding ).
The fourth bond on the carbon links it to a hydrogen (H) atom (for formic acid ), a methyl ( 2015; CH 3 ) group (for acetic acid ), or another natural or synthetic monovalent group. Carboxylic acids occur widely in nature. In fatty acids , the fourth group is a hydrocarbon chain. In aromatic acids (see aromatic compound ), it is a ring-structured hydrocarbon. In amino acids , it contains a nitrogen atom. Carboxylic acids participate in chemical reactions as acids , usually fairly weak. Many carboxylic acids (acetic acid, citric acid , lactic acid ) are intermediates in metabolism and can be found in natural products; others (e.g., salicylic acid ) are used as solvents and to prepare many chemical compounds. Important carboxylic-acid derivatives include esters , anhydrides , amides , halides (see halogen ), and salts (see soap ).