Editing Benzoic acid (section)

== Uses ==
Benzoic acid is mainly consumed in the production of [[phenol]] by [[oxidative decarboxylation]] at 300−400&nbsp;°C:<ref name=Ull>{{Ullmann|doi=10.1002/14356007.a03_555|chapter=Benzoic Acid and Derivatives|year=2000|last1=Maki|first1=Takao|last2=Takeda|first2=Kazuo|isbn=978-3527306732}}.</ref>
:{{chem2 | C6H5CO2H  + ½ O2 -> C6H5OH  +  CO2 }}
The temperature required can be lowered to 200&nbsp;°C by the addition of catalytic amounts of copper(II) salts. The phenol can be converted to [[cyclohexanol]], which is a starting material for [[nylon]] synthesis.

===Precursor to plasticizers===
Benzoate [[plasticizer]]s, such as the glycol-, diethyleneglycol-, and triethyleneglycol esters, are obtained by [[transesterification]] of [[methyl benzoate]] with the corresponding [[diol]].<ref name=Ull/> These plasticizers, which are used similarly to those derived from [[terephthalic acid]] ester, represent alternatives to [[phthalate]]s.<ref name=Ull/>

=== Precursor to sodium benzoate and related preservatives ===
Benzoic acid and its salts are used as [[food preservative]]s, represented by the [[E numbers]] [[E210]], [[sodium benzoate|E211]], [[potassium benzoate|E212]], and [[calcium benzoate|E213]]. Benzoic acid inhibits the growth of [[Mold (fungus)|mold]], [[yeast]]<ref>{{cite journal | author=A D Warth | title= Mechanism of action of benzoic acid on Zygosaccharomyces bailii: effects on glycolytic metabolite levels, energy production, and intracellular pH | journal=Appl Environ Microbiol | date=1 December 1991| volume=57|pages=3410–4 | pmid= 1785916 | issue=12 | doi= 10.1128/AEM.57.12.3410-3414.1991 | pmc=183988 | bibcode= 1991ApEnM..57.3410W }}</ref> and some [[bacteria]]. It is either added directly or created from reactions with its [[sodium]], [[potassium]], or [[calcium]] salt. The mechanism starts with the absorption of benzoic acid into the cell. If the intracellular [[pH]] changes to 5 or lower, the [[Fermentation (biochemistry)|anaerobic fermentation]] of [[glucose]] through [[phosphofructokinase]] is decreased by 95%. The efficacy of benzoic acid and benzoate is thus dependent on the pH of the food.<ref>{{cite journal |vauthors=Pastrorova I, de Koster CG, Boom JJ | title= Analytic Study of Free and Ester Bound Benzoic and Cinnamic Acids of Gum Benzoin Resins by GC-MS HPLC-frit FAB-MS | journal=Phytochem Anal | year=1997 | volume=8|pages=63–73 |doi= 10.1002/(SICI)1099-1565(199703)8:2<63::AID-PCA337>3.0.CO;2-Y | issue=2 }}</ref> Benzoic acid, benzoates 
and their derivatives are used as [[preservative]]s for acidic foods and beverages such as [[citrus fruit]] [[fruit juice|juice]]s ([[citric acid]]), sparkling drinks ([[carbon dioxide]]), [[soft drinks]] ([[phosphoric acid]]), [[Pickling|pickles]] ([[vinegar]]) and other acidified foods.

Typical [[Concentration|concentrations]] of benzoic acid as a preservative in food are between 0.05 and 0.1%. Foods in which benzoic acid may be used and maximum levels for its application are controlled by local food laws.<ref>[http://www.codexalimentarius.net/gsfaonline/groups/details.html?id=162 GSFA Online Food Additive Group Details: Benzoates (2006)] {{webarchive |url=https://web.archive.org/web/20070926233935/http://www.codexalimentarius.net/gsfaonline/groups/details.html?id=162 |date=26 September 2007 }}</ref><ref>[http://europa.eu.int/eur-lex/en/consleg/pdf/1995/en_1995L0002_do_001.pdf EUROPEAN PARLIAMENT AND COUNCIL DIRECTIVE No 95/2/EC of 20 February 1995 on food additives other than colours and sweeteners (Consleg-versions do not contain the latest changes in a law)] {{webarchive |url=https://web.archive.org/web/20030419083114/http://europa.eu.int/eur-lex/en/consleg/pdf/1995/en_1995L0002_do_001.pdf |date=19 April 2003 }}</ref>

Concern has been expressed that benzoic acid and its salts may react with [[ascorbic acid]] (vitamin C) in some soft drinks, forming small quantities of carcinogenic [[benzene]].<ref>{{cite web |url=http://www.bfr.bund.de/cm/245/indications_of_the_possible_formation_of_benzene_from_benzoic_acid_in_foods.pdf |archive-url=https://web.archive.org/web/20060426194742/http://www.bfr.bund.de/cm/245/indications_of_the_possible_formation_of_benzene_from_benzoic_acid_in_foods.pdf |archive-date=2006-04-26 |url-status=live |title=Indications of the possible formation of benzene from benzoic acid in foods, BfR Expert Opinion No. 013/2006 |publisher = German Federal Institute for Risk Assessment |date=1 December 2005 |access-date=30 March 2022}}</ref>
{{See also|Benzene in soft drinks}}

=== Medicinal ===
Benzoic acid is a constituent of [[Whitfield's ointment]] which is used for the treatment of fungal skin diseases such as [[ringworm]] and [[athlete's foot]].<ref>{{cite web |url=http://www.medipharmalimited.com/whitfield_ointment.asp |title=Whitfield Ointment |access-date=15 October 2007 |archive-url=https://web.archive.org/web/20071009152212/http://www.medipharmalimited.com/whitfield_ointment.asp |archive-date=9 October 2007 |url-status=dead }}</ref><ref>{{cite book | title = Wilson and Gisvold's Textbook of Organic Medicinal and Pharmaceutical | url = https://archive.org/details/wilsongisvoldste00bloc_128 | url-access = limited |author1=Charles Owens Wilson |author2=Ole Gisvold |author3=John H. Block | year = 2004 | publisher = Lippincott Williams & Wilkins | isbn = 978-0-7817-3481-3 | pages = [https://archive.org/details/wilsongisvoldste00bloc_128/page/n245 234]}}</ref> As the principal component of [[benzoin (resin)|gum benzoin]], benzoic acid is also a major ingredient in both [[tincture of benzoin]] and Friar's balsam.  Such products have a long history of use as topical [[antiseptic]]s and inhalant [[decongestant]]s.

Benzoic acid was used as an [[expectorant]], [[analgesic]], and [[antiseptic]] in the early 20th century.<ref>{{Cite journal|title=Troches of Benzoic Acid|url= https://books.google.com/books?id=cs3mAAAAMAAJ&pg=PA25|journal=Practical Druggist and Pharmaceutical Review of Reviews|last1=Lillard|first1=Benjamin|year=1919}}</ref>

===Niche and laboratory uses===
In teaching laboratories, benzoic acid is a common standard for calibrating a [[bomb calorimeter]].<ref>[http://www.uwlax.edu/faculty/loh/pdf_files/chm313_pdf/Manual_current/chm313_Expt2_bomb.pdf Experiment 2: Using Bomb Calorimetry to Determine the Resonance Energy of Benzene] {{webarchive|url=https://web.archive.org/web/20120309020205/http://www.uwlax.edu/faculty/loh/pdf_files/chm313_pdf/Manual_current/chm313_Expt2_bomb.pdf |date=9 March 2012 }}</ref>