Potassium benzoate

Potassium benzoate
Names
	IUPAC name Potassium benzoate
Identifiers
CAS Number	582-25-2 ;
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL2105241;
ChemSpider	10921 ;
ECHA InfoCard	100.008.621
EC Number	209-481-3;
E number	E212 (preservatives)
KEGG	D05576;
PubChem CID	23661960;
UNII	763YQN2K7K ;
CompTox Dashboard (EPA)	DTXSID1027219 ;
	InChI InChI=1S/C7H6O2.K/c8-7(9)6-4-2-1-3-5-6;/h1-5H,(H,8,9);/q;+1/p-1 Key: XAEFZNCEHLXOMS-UHFFFAOYSA-M ; 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;
	SMILES [K+].[O-]C(=O)c1ccccc1;
Properties
Chemical formula	C7H5KO2
Molar mass	160.213 g·mol−1
Appearance	White hygroscopic solid
Odor	Odorless
Density	1.5 g/cm3
Melting point	>300 °C (572 °F; 573 K)
Solubility in water	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)
Solubility in other solvents	Soluble in ethanol; Slightly soluble in methanol; Insoluble in ether
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Low toxicity
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319
Precautionary statements	P264, P280, P302+P352, P305+P351+P338, P332+P313, P337+P313, P362
NFPA 704 (fire diamond)	2 1 0
Autoignition; temperature	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). verify (what is ?) Infobox references

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.

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]

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] 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]

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.^[8]

Infrared spectrum

The following are the main peaks in the IR spectrum.^[8]

1610: C=O from carbonyl
1580: C=C from benzene ring

References

^ ^a ^b "Potassium Benzoate". Emerald Kalama Chemical. Retrieved 2014-06-02.
^ Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand. Retrieved 2014-05-29.
^ "Potassium benzoate". pubchem.ncbi.nlm.nih.gov.
^ Press Release from Defense Technical Information Center; article- Potassium Benzoate for Pyrotechnic Whistling Compositions: Its Synthesis and Characterization as an Anhydrous Salt
^ 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.
^ [1], The Food Magazine, Issue 77, Food Commission UK
^ ^a ^b SciFinder - Carbon-13 NMR Spectrum for 582-25-2

[info-1] "Potassium Benzoate". Emerald Kalama Chemical. Retrieved 2014-06-02.

[sioc-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] [1], The Food Magazine, Issue 77, Food Commission UK

[SciFinder-8] SciFinder - Carbon-13 NMR Spectrum for 582-25-2

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