A carboxylic acid (pron.: //) is an organic acid characterized
by the presence of at least one carboxyl group. The general
formula of a carboxylic acid is R-COOH, where R is some
monovalent functional group. A carboxyl group (or carboxy) is a
functional group consisting of a carbonyl (RR'C=O) and a
hydroxyl (R-O-H), which has the formula -C(=O)OH, usually
written as -COOH or -CO2H. Carboxylic acids are Brønsted-Lowry
acids because they are proton (H+) donors. They are the most
common type of organic acid. Among the simplest examples are
formic acid H-COOH, which occurs in ants, and acetic acid
CH3-COOH, which gives vinegar its sour taste. Acids with two or
more carboxyl groups are called dicarboxylic, tricarboxylic,
etc. The simplest dicarboxylic example is oxalic acid (COOH)2,
which is just two connected carboxyls. Mellitic acid is an
example of a hexacarboxylic acid. Other important natural
examples are citric acid (in lemons) and tartaric acid (in
tamarinds). Salts and esters of carboxylic acids are called