Potassium benzoate
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| IUPAC name
Potassium benzoate
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| Identifiers | |||
3D model (JSmol)
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| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.008.621 | ||
| EC Number |
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| E number | E212 (preservatives) | ||
| KEGG | |||
PubChem CID
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| UNII | |||
CompTox Dashboard (EPA)
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| Properties | |||
| C6H5COOK | |||
| Molar mass | 160.213 g·mol−1 | ||
| Appearance | White solid | ||
| Odor | Odorless | ||
| Density | 1.56 g/cm3 (20 °C (68 °F; 293 K)) | ||
| Melting point | >300 °C (572 °F; 573 K)[2] | ||
| Boiling point | >465 °C (869 °F; 738 K)[2] (decomposes) | ||
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| Solubility in ethanol | soluble | ||
| Solubility in methanol | slightly soluble | ||
| Solubility in ether | insoluble | ||
| Hazards | |||
| GHS labelling:[2] | |||
| Danger | |||
| H315, H318 | |||
| P264, P280, P302+P352, P305+P351+P338+P310, P332+P313, P362 | |||
| NFPA 704 (fire diamond) | |||
Threshold limit value (TLV)
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2.5 mg/m3 (skin)[3] (TWA) | ||
| Related compounds | |||
Other anions
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Other cations
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Potassium benzoate (E212), the potassium salt of benzoic acid with the formula C6H5COOK, is a food preservative that inhibits the growth of mold, yeast and some bacteria. It works best in low-pH products, below 4.5, where it exists as benzoic acid.
Acidic foods and beverages such as fruit juice (citric acid), sparkling drinks (carbonic acid), soft drinks (phosphoric acid), and pickles (vinegar) may be preserved with potassium benzoate. It is approved for use in most countries including Canada, the United States and the European Union, where it is designated by the E number E212.
Potassium benzoate is also used in whistle compositions in pyrotechnics. Compared to the other carboxylic acid salts, sodium salicylate and sodium benzoate often used for this purpose, it has the advantage of not being hygroscopic.[4]
Synthesis
One very common way to make potassium benzoate is by oxidizing toluene to benzoic acid followed by a neutralization with potassium hydroxide:[5]
- C6H5COOH + KOH → C6H5COOK + H2O
Another way to synthesize potassium benzoate in the lab setting is by hydrolyzing methyl benzoate with potassium hydroxide:
- C6H5COOCH3 + KOH → C6H5COOK + CH3OH
Reactions
Potassium benzoate, like sodium benzoate, can be decarboxylated with a strong base and heat:
- C6H5COOK + KOH → C6H6 + K2CO3
Mechanism of food preservation
The mechanism of food preservation begins with the absorption of benzoic acid into the cell. If the intracellular pH changes to 5 or lower, the anaerobic fermentation of glucose through phosphofructokinase is decreased by 95%.
Safety and health
Potassium benzoate has low acute toxicity upon oral and dermal exposure.[6] It is a mild irritant to the skin, and has the potential to cause serious eye damage.[2]
See also
References
- ^ Seidell, Atherton; Linke, William F. (1958). Solubilities of Inorganic and Organic Compounds; A Compilation of Quantitative Solubility Data From the Periodical Literature (4th ed.). Van Nostrand. p. 1352. OL 47062711M. Retrieved 19 March 2026.
- ^ a b c d "Safety Data Sheet: Potassium Benzoate". www.sigmaaldrich.com. Sigma-Aldrich. p. 6.
- ^ a b "SDS - Potassium Benzoate" (pdf). www.thermofisher.com. ThermoFisher Scientific. 24 December 2025. pp. 2–3. Retrieved 19 March 2026.
- ^ Whelan, D.J.; Elischer, P.P. (February 1983). "Potassium Benzoate for Pyrotechnic Whistling Compositions: Its Synthesis and Characterization as an Anhydrous Salt". apps.dtic.mil. Melbourne, Victoria, Australia: Department of Defence, Defence Science and Technology Organisation, Materials Research Labs. Retrieved 27 July 2025.
- ^ US 3867439, Hills, David J., "Preparation of potassium benzoate", published 1975-02-18, assigned to The Dow Chemical Company
- ^ "Benzoates" (PDF). United Nations Environment Programme. Archived from the original (PDF) on 2018-03-07. Retrieved 2015-04-30.