POTASSIUM BENZOATE: STRUCTURE, PROPERTIES, PRODUCTION, USES - CHEMISTRY - 2025

The benzoate is an organic compound consisting of a potassium ion K ⁺ and benzoate ion C ₆ H ₅ COO ^-. Its chemical formula is C ₆ H ₅ COOK or the condensed formula C ₇ H ₅ KO ₂. It is a white crystalline solid. It is hygroscopic, which means that it absorbs water from the air.

Aqueous solutions of potassium benzoate are slightly alkaline. In an acid medium, the benzoate ion (C ₆ H ₅ COO ^-) tends to take a proton and turn into benzoic acid (C ₆ H ₅ COOH).

Potassium benzoate C ₆ H ₅ COOK solid. W. Oelen. Source: Wikimedia Commons.

Potassium benzoate is used as a food preservative, especially when it is desired that these are sodium (Na) free. It prevents food from spoiling due to microorganisms.

It is used in cold cuts, processed soft drinks, and bakery products, among other foods. Probably its preservative action is due to benzoic acid (C ₆ H ₅ COOH) that is formed at low pH, which prevents the reproduction of fungi and bacteria.

Although potassium benzoate is approved by health organizations, it is advisable not to abuse its use, since it has been found that it can affect the fetuses of mice.

Structure

Potassium benzoate is an organic salt, that is, a salt of a carboxylic acid, as it is the potassium salt of benzoic acid. It is made up of a K + potassium cation and a C ₆ H ₅ COO ^- benzoate anion.

The benzoate anion C ₆ H ₅ COO ^- is formed by a benzene ring C ₆ H ₅ - and a carboxylate group –COO ^-.

Chemical structure of potassium benzoate. Edgar181. Source: Wikimedia Commons.

The bond between these two ions is a strong electrostatic bond that holds them in the crystal lattice.

3D structure of potassium benzoate. Black = carbon; white = hydrogen; red = oxygen; violet = potassium. Claudio Pistilli. Source: Wikimedia Commons.

Nomenclature

• Potassium benzoate
• Potassium salt of benzoic acid

Properties

Physical state

Crystalline white solid.

Molecular weight

160.212 g / mol

Solubility

Soluble in water.

pH

Aqueous solutions of potassium benzoate are slightly basic.

Chemical properties

It is hygroscopic, that is, it is a solid that absorbs water from the environment easily.

The bond between the potassium ion K ⁺ and the benzoate ion C ₆ H ₅ COO ^- as in most ionic compounds can be overcome only by a high temperature or by a very polar solvent such as water.

The benzoate anion C ₆ H ₅ COO ^- is moderately basic, with an appreciable tendency to combine with protons. It reacts with water taking a proton H ⁺ to form benzoic acid (C ₆ H ₅ COOH) and this leads to an increase in the concentration of OH ^- ions.

C ₆ H ₅ COO ^- + H ₂ O ⇔ C ₆ H ₅ COOH + OH ^-

For this reason, aqueous solutions of potassium benzoate are slightly alkaline.

Obtaining

To prepare potassium benzoate, benzoic acid (C ₆ H ₅ COOH) is neutralized with potassium carbonate (K ₂ CO ₃) in a minimum volume of water to obtain a clear solution from which the salt crystallizes.

2 C ₆ H ₅ COOH + K ₂ CO ₃ → 2 C ₆ H ₅ COO ^- K ⁺ + H ₂ O + CO ₂ ↑

Then the crystallized potassium benzoate salt is washed several times with ether and dried.

Applications

In the processed food industry

Potassium benzoate is widely used as an antimicrobial agent for the preservation of beverages, fruit derivatives, bakery products and other foods.

Some bakery products may contain potassium benzoate. Author: Andrew Martin. Source: Pixabay.

It is a food preservative, capable of inhibiting, slowing down or slowing down the fermentation, acidification or deterioration process of food due to some fungi and bacteria.

According to the Environmental Protection Agency or EPA, potassium benzoate has been verified as a compound of little concern to human health.

Against fungi

It is an antifungal agent, as it can destroy them by suppressing their ability to grow or reproduce. It is not a fungicide for animal or human body tissues, but an inhibitor that slows or slows the growth of fungi in food or drink.

Some types of mold produce substances called aflatoxins, which are a threat to both humans and animals because they are toxic, can cause cancer and mutations.

Most molds are inhibited at concentrations of 0.05-0.10% potassium benzoate. The performance of this depends on the pH, because at a lower pH it is more effective as an antifungal.

Processed sodas may contain potassium benzoate. Author: Lisakara. Source: Pixabay.

This is because the antifungal action actually resides in benzoic acid C ₆ H ₅ COOH, which is the conjugated acid of potassium benzoate. This acid is formed at low pH, that is, in the presence of a large amount of hydrogen ions H ⁺:

Potassium benzoate + Hydrogen ions → Benzoic acid + Potassium ions

C ₆ H ₅ COOK + H ⁺ → C ₆ H ₅ COOH + K ⁺

According to some researchers, its effectiveness is due in part to the solubility of benzoic acid in the cell membrane of the microorganism. This type of acid increases the flow of protons through this membrane.

This causes the disruption or disorganization of certain functions of the fungal cell.

Against bacteria

It is an agent that works against some bacteria. It is added to foods such as processed sausages, processed hams (ready to eat), and some beverages.

It has been tested against Listeria monocytogenes, a bacterium that can kill humans who eat food contaminated with it. It produces fever, vomiting and diarrhea, among other symptoms.

It has been found that foods treated with potassium benzoate and that have been contaminated with Listeria must be kept at temperatures below -2.2 ° C so that this bacterium does not reproduce.

Hot dogs and other stuffed meats may contain potassium benzoate. Author: Selling of my photos with StockAgencies is not permitted. Source: Pixabay.

On the other hand, the use of electron radiation has been tried to intensify the effect of potassium benzoate against bacteria, but it has been determined that C ₆ H ₆ benzene is produced, which is a toxic compound.

Therefore, although foods contain potassium benzoate, it is recommended that they be preferably cooked at high temperatures before being consumed, to eliminate any type of danger derived from the presence of pathogenic bacteria.

In various applications

According to sources consulted, potassium benzoate is also used in adhesives and binding agents for a variety of uses. It is added to cigarettes and tobacco or is related to the manufacture of these.

It is used in personal care products such as cosmetics, shampoo, perfumes, soaps, lotions, etc. It is also part of paints and coatings.

Negative effects of ingesting foods with potassium benzoate

Certain researchers found that potassium benzoate produced harmful effects on the fetuses of mice.

Although no effects were observed on adult mice exposed to potassium benzoate, malformations were found in the eyes of the fetuses and a marked decrease in weight and length of the little bodies of the mouse fetuses.

According to laboratory experiences, the fetuses of mice can be affected by the potassium benzoate ingested by the mother. Author: Tibor Janosi Mozes. Source: Pixabay.

This means that fetuses are more sensitive to potassium benzoate than adult mice.

References

1. Mandal, PK et al. (1978). Viscosity Behavior of Benzoic Acid and Benzoate Ion in Aqueous Solution. Journal of Solution Chemistry, Vol. 7, No. 1, 1978. Recovered from link.springer.com.
2. Rusul, G. and Marth, EH (1987). Growth and Aflatoxin Production by Aspergillus parasiticus NRRL 2999 in the Presence of Potassium Bnezoate or Potassium Sorbate and at Different Initial pH Values. J Food Prot. 1987; 50 (10): 820-825. Recovered from ncbi.nlm.nih.gov.
3. Lu, Z. et al. (2005). Inhibitory Effects of Organic Acid Salts for Control of Listeria monocytogenes on Frankfurters. J Food Prot. 2005; 68 (3): 499-506. Recovered from ncbi.nlm.nih.gov.
4. Zhu, MJ et al. (2005). Impact of Antimicrobial ingredients and Irradiation on the Survival of Listeria monocytogenes and the Quality of Ready-to-Eat Turkey Ham. Poult Sci. 2005; 84 (4): 613-20. Recovered from ncbi.nlm.nih.gov.
5. US National Library of Medicine. (2019). Potassium benzoate. Recovered from pubchem.ncbi.nlm.nih.gov.
6. Afshar, M. et al. (2013). Teratogenic Effects of Long Term Consumption of Potassium Benzoate on Eye Development in Balb / c Fetal Mice. Iran J Basic Med Sci. 2013; 16 (4): 584-589. Recovered from ncbi.nlm.nih.gov.
7. Lide, DR (editor) (2003). CRC Handbook of Chemistry and Physics. 85 ^th CRC Press.
8. Morrison, RT and Boyd, RN (2002). Organic Chemistry. 6th Edition. Prentice-Hall.