Organic acid

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 –SO2OH, 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 ester group, and the amide group. In biological systems, organic compounds containing these groups are generally referred to as organic acids.

Classification

Organic acids are classified into aliphatic acids, aromatic acids, alicyclic acids, and heterocyclic acids.

Properties

Organic acids are usually weak, meaning that they do not fully dissociate into their ions in water. Lower molecular mass organic acids such as formic acid and lactic acid are miscible in water and are quite polar, meaning they tend to be soluble in water. Higher molecular mass organic acids, such as benzoic acid, are much less soluble due to the larger nonpolar aliphatic region.

Applications

Organic acids are used in food preservation because of their effects on bacteria. The key advantage of using organic acids such as fumaric acid, acetic acid, and lactic acid is that they maintain the fresh flavor of the food product while providing increased shelf life.

See also

• List of carboxylic acids
• Acid strength
• Acid dissociation constant
• Acid-base reaction theories

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  Weak Organic Acids
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  Strong Organic Acids