Benzoic acid is a simple aromatic carboxylic acid with aromaticity and the property of carboxylic acid. Therefore, two types of chemical reactions can occur, one is substitution reaction on benzene ring and the other is reaction of carboxylic group.

Benzoic acid - acid

The ionization constant of benzoic acid in water Ka= 6.4×10-5 (25℃), and benzoic acid is slightly more acidic than cyclohexane acid, which is due to the large electronegativity of sp2 hybridized carbon atoms on the benzene ring and the weak electron giving effect.

Benzoic acid can be used as a preservative in food, feed, latex and toothpaste.Under acidic conditions, it had inhibitory effect on mold, yeast and bacteria, but it had weak effect on acidogenic bacteria.The molecular state of benzoic acid has a higher antibacterial activity than the ionic state, so when the PH is less than 4, the antibacterial activity is high, and the optimal antibacterial PH value is 2.5 ~ 4.0, generally lower than the PH value of 4.5 ~ 5.0 is appropriate.Because of the low solubility of benzoic acid to water, in fact, it is usually dissolved by adding an appropriate amount of sodium carbonate or sodium bicarbonate in hot water above 90℃, and then converted into sodium benzoate before it is added into food.If benzoic acid must be used, it can be dissolved with an appropriate amount of alcohol before application.Since benzoic acid is less soluble to water than sodium benzoate, care should be taken to prevent precipitation and reduce the effectiveness of benzoate when using sodium benzoate in acidic foods.Benzoic acid can be used in soy sauce and cool drinks together with p-hydroxybenzoic acid esters to enhance the effectiveness.

Formic acid

Formic acid (chemical formula HCOOH, molecular formula CH2O2, molecular weight 46.03), colloquial name formic acid, is the simplest carboxylic acid.A colorless liquid with a pungent odor.

Formic acid is a weak electrolyte, melting point 8.6℃, boiling point 100.8℃.Acidity is very strong, corrosive, can irritate skin bubble.Found in the secretions of bees, certain ants, and caterpillars.Is an organic chemical raw material, also used as a disinfectant and antiseptic.