An
organic acid is an
organic compound with
acidic properties. The most common organic acids are the
carboxylic acids, whose acidity is associated with their
carboxyl group –COOH.
Sulfonic acids, containing the group –SO
2OH, are relatively stronger acids. Alcohols, with
–OH, can act as acids but they are usually very weak. The relative stability of the conjugate base of the acid determines its acidity. Other groups can also confer acidity, usually weakly: the
thiol group –SH, the
enol group, and the
phenol group. In biological systems, organic compounds containing these groups are generally referred to as organic acids.