Organic acid The term used for organic compounds with acidic properties. The most common organic acids are carboxylic acids whose acidity is related to the carboxyl group (–COOH). Sulfonoic acids are stronger acids than carboxylic acids. Alcohols can act as acids but generally have a very weak acidity. The relative stability of the conjugated base of the acid determines its acidity. It can also determine acidity in other groups, such as thiol, enol, phenol, and the -SH group, although they generally have little effect. In biological systems, organic compounds containing the mentioned organic groups generally correspond to organic acids.