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Potassium benzoate

Chemical compound From Wikipedia, the free encyclopedia

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.

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Potassium benzoate
Names
IUPAC name
Potassium benzoate
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.008.621 Edit this at Wikidata
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
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)[1]
Boiling point >465 °C (869 °F; 738 K)[1] (decomposes)
  • 5.04 g/100g (0.86 °C (33.55 °F; 274.01 K), solid)
  • 39.89 g/100g (8.5 °C (47.3 °F; 281.6 K), melting point)
  • 40.6 g/100g (13.0 °C (55.4 °F; 286.1 K))
  • 44.92 g/100g (41.0 °C (105.8 °F; 314.1 K))
  • 53.5 g/100g (97.5 °C (207.5 °F; 370.6 K))
  • 66.09 g/100g (181.0 °C (357.8 °F; 454.1 K))[2]
Solubility in ethanol soluble
Solubility in methanol slightly soluble
Solubility in ether insoluble
Hazards
GHS labelling:[1]
GHS05: Corrosive
Danger
H315, H318
P264, P280, P302+P352, P305+P351+P338+P310, P332+P313, P362
NFPA 704 (fire diamond)
[3]
NFPA 704 four-colored diamondHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
0
1
1
2.5 mg/m3 (skin)[3] (TWA)
Related compounds
Other anions
Other cations
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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:[citation needed]

C6H5COOCH3 + KOH → C6H5COOK + CH3OH

Reactions

Potassium benzoate, like sodium benzoate, can be decarboxylated with a strong base and heat, [citation needed] or in the absence of base, through pyrolysis between 435 and 500 °C.[6]

C6H5COOK → C6H5· + CO2
C6H5· + H2O → C6H6

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%.[citation needed]

Safety and health

Potassium benzoate has low acute toxicity upon oral and dermal exposure.[7] It is a mild irritant to the skin, and has the potential to cause serious eye damage.[1]

See also

References

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