Products
Pure benzoic acid is available as an open product in pharmacies and drugstores. It is found in liquid, semi-solid and solid medicines.
Structure and properties
Benzoic acid (C7H6O2, Mr = 122.1 g/mol) exists as a white, odorless, crystalline powder or as colorless crystals and is sparingly soluble in water. In contrast, it is more soluble in hot water. It is a simple aromatic carboxylic acid. The carboxy group is directly attached to the benzene ring instead of a hydrogen atom. The pKa of the acid is 4.2. The salts (and incidentally also the esters) are called benzoates, for example sodium benzoate (E 211), potassium benzoate (E 212) and calcium benzoate (E 213). They are generally more soluble in water. Benzoic acid is a natural substance that also occurs in plants and certain berries, such as cranberries. The name is derived from the benzoic resin, which contains a high proportion. Benzyl alcohol can be oxidized to benzaldehyde and to benzoic acid, for example with oxygen and a catalyst:
Effects
Benzoic acid has antibacterial and antifungal (antifungal) properties. It is effective protonated at a low pH in the acidic range (< 4.5).
Fields of application
Fields of application include (selection):
- As a preservative for food, beverages, pharmaceuticals and cosmetics (E 210). The salts are also used for this purpose.
- More rarely, benzoic acid is also used as an antimicrobial agent.
- For chemical syntheses.
Adverse effects
Intolerance reactions may occur in sensitive individuals.
