Potassium benzoate

Potassium benzoate (E212), the potassium salt of benzoic acid, 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.

Potassium benzoate
Names
IUPAC name
Potassium benzoate
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.008.621
EC Number
  • 209-481-3
E number E212 (preservatives)
KEGG
UNII
  • InChI=1S/C7H6O2.K/c8-7(9)6-4-2-1-3-5-6;/h1-5H,(H,8,9);/q;+1/p-1 checkY
    Key: XAEFZNCEHLXOMS-UHFFFAOYSA-M checkY
  • InChI=1/C7H6O2.K/c8-7(9)6-4-2-1-3-5-6;/h1-5H,(H,8,9);/q;+1/p-1
    Key: XAEFZNCEHLXOMS-REWHXWOFAQ
  • [K+].[O-]C(=O)c1ccccc1
Properties
C7H5KO2
Molar mass 160.213 g·mol−1
Appearance White hygroscopic solid
Odor Odorless[1]
Density 1.5 g/cm3
Melting point >300 °C (572 °F; 573 K)
69.87 g/100 mL (17.5 °C)
73.83 g/100 mL (25 °C)
79 g/100 mL (33.3 °C)
88.33 g/100 mL (50 °C)[2][1]
Solubility in other solvents Soluble in ethanol
Slightly soluble in methanol
Insoluble in ether
Hazards[3]
Occupational safety and health (OHS/OSH):
Main hazards
 Low toxicity
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319
P264, P280, P302+P352, P305+P351+P338, P332+P313, P337+P313, P362
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
2
1
0
950 °C (1,740 °F; 1,220 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

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 the whistle in many fireworks.[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]

Another way to synthesize potassium benzoate in the lab setting is by hydrolyzing methyl benzoate with potassium hydroxide:

Reactions

Potassium benzoate, like sodium benzoate, can be decarboxylated with a strong base and heat:

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] The Food Commission, which campaigns for safer, healthier food in the UK, describes potassium benzoate as "mildly irritant to the skin, eyes and mucous membranes".[7]

Cats have a significantly lower tolerance to benzoic acid and its salts than rats and mice.[8]

Under certain circumstances, such as in the presence of ascorbic acid, benzoate salts can produce benzene in soft drinks. The US Food and Drug Administration states the levels of benzene measured do not pose a safety concern for consumers.[9]

Spectra

Carbon-13 NMR

The carbon-13 NMR shows 5 unique peaks. There are four peaks between 130-140 ppm from the carbon atoms in the benzene ring. There is an additional carbon peak around 178 ppm representing the carbon atom from the carbonyl group.[10]

Infrared spectrum

The following are the main peaks in the IR spectrum.[10]

See also

References
  1. "Potassium Benzoate". Emerald Kalama Chemical. Retrieved 2014-06-02.
  2. Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand. Retrieved 2014-05-29.
  3. "Potassium benzoate". pubchem.ncbi.nlm.nih.gov.
  4. Press Release from Defense Technical Information Center; article- Potassium Benzoate for Pyrotechnic Whistling Compositions: Its Synthesis and Characterization as an Anhydrous Salt
  5. US 3867439, Hills, David J., "Preparation of potassium benzoate", published 1975-02-18, assigned to The Dow Chemical Company
  6. "Benzoates" (PDF). United Nations Environment Programme. Archived from the original (PDF) on 2018-03-07. Retrieved 2015-04-30.
  7. , The Food Magazine, Issue 77, Food Commission UK
  8. Bedford PG, Clarke EG (1972). "Experimental benzoic acid poisoning in the cat". Vet Rec. 90 (3): 53–58. doi:10.1136/vr.90.3.53. PMID 4672555. S2CID 2553612.
  9. "Questions and Answers on the Occurrence of Benzene in Soft Drinks and Other Beverages". Food and Drug Administration. ...the levels of benzene found in beverages to date do not pose a safety concern for consumers.
  10. SciFinder - Carbon-13 NMR Spectrum for 582-25-2
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