| PIN = Benzoic acid<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 745 | doi = 10.1039/9781849733069-00648 | isbn = 978-0-85404-182-4 }}</ref>
| PIN = Benzoic acid<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book) | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 745 | doi = 10.1039/9781849733069-00648 | isbn = 978-0-85404-182-4 }}</ref>
| SystematicName = Benzenecarboxylic acid
| SystematicName = Benzenecarboxylic acid
| OtherNames = {{ubl
| OtherNames = {{ubl
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| Appearance = Colorless crystalline solid
| Appearance = Colorless crystalline solid
| Odor = Faint, pleasant odor
| Odor = Faint, pleasant odor
| Density = 1.2659{{nbsp}}g/cm<sup>3</sup> (15 °C)<br> 1.0749{{nbsp}}g/cm<sup>3</sup> (130 °C)<ref name=chemister />
| Density = 1.2659 g/cm<sup>3</sup> (15 °C)<br/> 1.0749 g/cm<sup>3</sup> (130 °C)<ref name=chemister />
| Solubility = 1.7{{nbsp}}g/L (0 °C)<br> 2.7{{nbsp}}g/L (18 °C)<br> 3.44{{nbsp}}g/L (25 °C)<br> 5.51{{nbsp}}g/L (40 °C)<br> 21.45{{nbsp}}g/L (75 °C)<br> 56.31{{nbsp}}g/L (100 °C)<ref name=chemister>{{cite web|url=http://chemister.ru/Database/properties-en.php?dbid=1&id=679|title=benzoic acid|website=chemister.ru|access-date=24 October 2018}}</ref><ref name=sioc>{{cite book|last1 = Seidell|first1 = Atherton|last2 = Linke|first2 = William F.|year = 1952|title = Solubilities of Inorganic and Organic Compounds|publisher = Van Nostrand|url = https://books.google.com/books?id=k2e5AAAAIAAJ}}</ref>
| Solubility = 1.7 g/L (0 °C)<br/> 2.7 g/L (18 °C)<br/> 3.44 g/L (25 °C)<br/> 5.51 g/L (40 °C)<br/> 21.45 g/L (75 °C)<br/> 56.31 g/L (100 °C)<ref name=chemister>{{cite web |url=http://chemister.ru/Database/properties-en.php?dbid=1&id=679 |title=benzoic acid |website=chemister.ru |access-date=24 October 2018}}</ref><ref name=sioc>{{cite book |last1 = Seidell |first1 = Atherton |last2 = Linke |first2 = William F. |year = 1952 |title = Solubilities of Inorganic and Organic Compounds |publisher = Van Nostrand |url = https://books.google.com/books?id=k2e5AAAAIAAJ}}</ref>
| pKa = {{ubl
| pKa = {{ubl
| 4.202 (H<sub>2</sub>O)<ref>{{cite book|last=Harris|first=Daniel|title=Quantitative Chemical Analysis|year=2010|publisher=W. H. Freeman and Company|location=New York|isbn=9781429254366|pages=AP12|edition=8}}</ref>
| 4.202 (H<sub>2</sub>O)<ref>{{cite book |last=Harris |first=Daniel |title=Quantitative Chemical Analysis |year=2010 |publisher=W. H. Freeman and Company |location=New York |isbn=9781429254366 |page=AP12 |edition=8}}</ref>
| 11.02 (DMSO)<ref>{{cite journal |last1=Olmstead |first1=William N. |last2=Bordwell |first2=Frederick G. |title=Ion-pair association constants in dimethyl sulfoxide |journal=The Journal of Organic Chemistry |date=1980 |volume=45 |issue=16 |pages=3299–3305 |doi=10.1021/jo01304a033}}</ref>
| 11.02 (DMSO)<ref>{{cite journal |last1=Olmstead |first1=William N. |last2=Bordwell |first2=Frederick G. |title=Ion-pair association constants in dimethyl sulfoxide |journal=The Journal of Organic Chemistry |date=1980 |volume=45 |issue=16 |pages=3299–3305 |doi=10.1021/jo01304a033}}</ref>
'''Benzoic acid''' ({{IPAc-en|b|ɛ|n|ˈ|z|oʊ|.|ɪ|k}}) is a white (or colorless) solid [[organic compound]] with the formula {{chem2|C6H5COOH}}, whose [[Chemical structure|structure]] consists of a [[benzene]] ring ({{chem2|C6H6}}) with a [[carboxyl]] ({{chem2|\sC(\dO)OH}}) [[substituent]]. The [[benzoyl]] group is often abbreviated "Bz" (not to be confused with "Bn," which is used for [[benzyl]]), thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula –{{chem2|C6H5CO}}. It is the simplest [[aromaticity|aromatic]] carboxylic acid. The name is derived from [[benzoin (resin)|gum benzoin]], which was for a long time its only source.
'''Benzoic acid''' ({{IPAc-en|b|ɛ|n|ˈ|z|oʊ|.|ɪ|k}}) is a white or colorless crystalline [[organic compound]] with the formula {{chem2|C6H5COOH}}, whose [[Chemical structure|structure]] consists of a [[benzene]] ring ({{chem2|C6H6}}) with a [[carboxyl]] ({{chem2|\sC(\dO)OH}}) [[substituent]]. The [[benzoyl]] group is often abbreviated "Bz" (not to be confused with "Bn", which is used for [[benzyl]]), thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula −{{chem2|C6H5CO}}. It is the simplest [[aromaticity|aromatic]] carboxylic acid. The name is derived from [[benzoin (resin)|gum benzoin]], which was for a long time its only source.
Benzoic acid occurs naturally in many plants<ref>{{cite web | title = Scientists uncover last steps for benzoic acid creation in plants | url = http://www.purdue.edu/newsroom/releases/2012/Q3/scientists-uncover-last-steps-for-benzoic-acid-creation-in-plants.html | publisher = Purdue Agriculture News}}</ref> and serves as an intermediate in the biosynthesis of many [[secondary metabolite]]s. [[salt (chemistry)|Salts]] of benzoic acid are used as [[food preservative]]s. Benzoic acid is an important [[Precursor (chemistry)|precursor]] for the industrial synthesis of many other organic substances. The salts and [[ester]]s of benzoic acid are known as '''benzoates''' ({{IPAc-en|ˈ|b|ɛ|n|z|oʊ|.|eɪ|t|s}}).
Benzoic acid occurs naturally in many plants<ref>{{cite web | title = Scientists uncover last steps for benzoic acid creation in plants | url = https://www.purdue.edu/newsroom/releases/2012/Q3/scientists-uncover-last-steps-for-benzoic-acid-creation-in-plants.html | publisher = Purdue Agriculture News}}</ref> and serves as an intermediate in the biosynthesis of many [[secondary metabolite]]s. [[salt (chemistry)|Salts]] of benzoic acid are used as [[food preservative]]s. Benzoic acid is an important [[Precursor (chemistry)|precursor]] for the industrial synthesis of many other organic substances. The salts and [[ester]]s of benzoic acid are known as '''benzoates''' ({{IPAc-en|ˈ|b|ɛ|n|z|oʊ|.|eɪ|t|s}}).
== History ==
== History ==
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}}</ref> These latter also investigated how [[hippuric acid]] is related to benzoic acid.
}}</ref> These latter also investigated how [[hippuric acid]] is related to benzoic acid.
In 1875 Salkowski discovered the [[Antifungal medication|antifungal]] properties of benzoic acid, which explains the preservation of benzoate-containing [[Cloudberry|cloudberry fruits]].<ref>{{cite journal | author= Salkowski E| journal=Berl Klin Wochenschr| year=1875 | volume=12 | pages=297–298}}</ref>{{Disputed inline|Salkowski reference|date=March 2022}}
In 1875 Salkowski discovered the [[Antifungal medication|antifungal]] properties of benzoic acid, which explains the preservation of benzoate-containing [[Cloudberry|cloudberry fruits]].<ref>{{cite journal | author= Salkowski E| journal=Berl Klin Wochenschr| year=1875 | volume=12 | pages=297–298}}</ref><ref>{{cite web |title=Cloudberries Cooperative Extension Service |url=https://www.uaf.edu/ces/publications/database/food/cloudberries.php |website=www.uaf.edu}}</ref>
== Production ==
== Production ==
=== Industrial preparations ===
=== Industrial preparations ===
Benzoic acid is produced commercially by [[partial oxidation]] of [[toluene]] with [[oxygen]]. The process is catalyzed by [[cobalt]] or [[manganese]] [[naphthenate]]s. The process uses abundant materials, and proceeds in high yield.<ref>{{cite book|last1=Wade|first1=Leroy G.|title=Organic Chemistry|date=2014|publisher=Pearson Education Limited|location=Harlow|isbn=978-1-292-02165-2|page=985|edition=Pearson new international |ref=OrgChem}}</ref>
Benzoic acid is produced commercially by [[partial oxidation]] of [[toluene]] with [[oxygen]]:
The process is catalyzed by [[cobalt]] or [[manganese]] [[naphthenate]]s. The process uses abundant materials and proceeds in high yield.<ref>{{cite book |last1=Wade |first1=Leroy G. |title=Organic Chemistry |date=2014 |publisher=Pearson Education Limited |location=Harlow |isbn=978-1-292-02165-2 |page=985 |edition=Pearson new international |ref=OrgChem}}</ref>
The first industrial process involved the reaction of [[benzotrichloride]] (trichloromethyl benzene) with [[calcium hydroxide]] in water, using [[iron]] or iron salts as [[catalyst]]. The resulting [[calcium benzoate]] is converted to benzoic acid with [[hydrochloric acid]]. The product contains significant amounts of [[Halogenation|chlorinated]] benzoic acid derivatives. For this reason, benzoic acid for human consumption was obtained by dry distillation of [[Benzoin (resin)|gum benzoin]]. Food-grade benzoic acid is now produced synthetically.
The first industrial process involved the reaction of [[benzotrichloride]] (trichloromethyl benzene) with [[calcium hydroxide]] in water, using [[iron]] or iron salts as [[catalyst]]. The resulting [[calcium benzoate]] is converted to benzoic acid with [[hydrochloric acid]]. The product contains significant amounts of [[Halogenation|chlorinated]] benzoic acid derivatives. For this reason, benzoic acid for human consumption was obtained by dry distillation of [[Benzoin (resin)|gum benzoin]]. Food-grade benzoic acid is now produced synthetically.
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== Uses ==
== Uses ==
Benzoic acid is mainly consumed in the production of [[phenol]] by [[oxidative decarboxylation]] at 300−400 °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>
Benzoic acid is mainly consumed in the production of [[phenol]] by [[oxidative decarboxylation]] at 300–400 °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 }}
: {{chem2 | C6H5CO2H + ½ O2 -> C6H5OH + CO2 }}
The temperature required can be lowered to 200 °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.
The temperature required can be lowered to 200 °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.
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=== Precursor to sodium benzoate and related preservatives ===
=== 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
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.
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>
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>
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>
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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 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>
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===
===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>
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>
== Biology and health effects ==
== Biology and health effects ==
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It is excreted as [[hippuric acid]].<ref>{{cite journal | author= Cosmetic Ingredient Review Expert Panel Bindu Nair | title= Final Report on the Safety Assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate| journal=Int J Tox | year=2001 | volume= 20 | issue=Suppl. 3 | pages=23–50 | doi= 10.1080/10915810152630729 | pmid= 11766131| s2cid= 13639993}}</ref> Benzoic acid is metabolized by [[butyrate-CoA ligase]] into an intermediate product, [[benzoyl-CoA]],<ref name="Benzoic1">{{cite web| title=butyrate-CoA ligase| url=http://www.brenda-enzymes.org/php/result_flat.php4?ecno=6.2.1.2&Suchword=&organism%5B%5D=Homo+sapiens&show_tm=0| website=BRENDA| publisher=Technische Universität Braunschweig.| access-date=7 May 2014}} Substrate/Product</ref> which is then metabolized by [[glycine N-acyltransferase|glycine ''N''-acyltransferase]] into hippuric acid.<ref name="Benzoic2">{{cite web| title=glycine N-acyltransferase|url=http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.13&Suchword=&organism%5B%5D=Homo+sapiens&show_tm=0|website=BRENDA|publisher=Technische Universität Braunschweig.|access-date=7 May 2014}} Substrate/Product</ref> Humans metabolize [[toluene]] which is also excreted as hippuric acid.<ref>{{cite journal |vauthors=Krebs HA, Wiggins D, Stubbs M | title= Studies on the mechanism of the antifungal action of benzoate | journal= Biochem J | year=1983 | volume=214 | pages=657–663| pmid=6226283 | issue=3 | pmc=1152300 | doi= 10.1042/bj2140657 }}</ref>
It is excreted as [[hippuric acid]].<ref>{{cite journal | author= Cosmetic Ingredient Review Expert Panel Bindu Nair | title= Final Report on the Safety Assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate| journal=Int J Tox | year=2001 | volume= 20 | issue=Suppl. 3 | pages=23–50 | doi= 10.1080/10915810152630729 | pmid= 11766131| s2cid= 13639993}}</ref> Benzoic acid is metabolized by [[butyrate-CoA ligase]] into an intermediate product, [[benzoyl-CoA]],<ref name="Benzoic1">{{cite web| title=butyrate-CoA ligase| url=http://www.brenda-enzymes.org/php/result_flat.php4?ecno=6.2.1.2&Suchword=&organism%5B%5D=Homo+sapiens&show_tm=0| website=BRENDA| publisher=Technische Universität Braunschweig.| access-date=7 May 2014}} Substrate/Product</ref> which is then metabolized by [[glycine N-acyltransferase|glycine ''N''-acyltransferase]] into hippuric acid.<ref name="Benzoic2">{{cite web| title=glycine N-acyltransferase|url=http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.3.1.13&Suchword=&organism%5B%5D=Homo+sapiens&show_tm=0|website=BRENDA|publisher=Technische Universität Braunschweig.|access-date=7 May 2014}} Substrate/Product</ref> Humans metabolize [[toluene]] which is also excreted as hippuric acid.<ref>{{cite journal |vauthors=Krebs HA, Wiggins D, Stubbs M | title= Studies on the mechanism of the antifungal action of benzoate | journal= Biochem J | year=1983 | volume=214 | pages=657–663| pmid=6226283 | issue=3 | pmc=1152300 | doi= 10.1042/bj2140657 }}</ref>
For humans, the [[World Health Organization]]'s [[International Programme on Chemical Safety]] (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.<ref name="concise">{{cite web|url=http://www.inchem.org/documents/cicads/cicads/cicad26.htm|title= Concise International Chemical Assessment Document 26: BENZOIC ACID AND SODIUM BENZOATE}}</ref> [[Cat]]s have a significantly lower tolerance against benzoic acid and its [[Salt (chemistry)|salts]] than [[rat]]s and [[mouse|mice]]. Lethal dose for cats can be as low as 300 mg/kg body weight.<ref>{{cite journal| doi= 10.1136/vr.90.3.53|vauthors=Bedford PG, Clarke EG |title=Experimental benzoic acid poisoning in the cat|journal=Vet Rec |year=1972|pages=53–58|volume=90 |pmid = 4672555| issue= 3|doi-broken-date=11 July 2025 |s2cid=2553612 }}</ref> The oral {{LD50}} for rats is 3040 mg/kg, for mice it is 1940–2263 mg/kg.<ref name="concise" />
For humans, the [[World Health Organization]]'s [[International Programme on Chemical Safety]] (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.<ref name="concise">{{cite web|url=https://www.inchem.org/documents/cicads/cicads/cicad26.htm|title= Concise International Chemical Assessment Document 26: BENZOIC ACID AND SODIUM BENZOATE}}</ref> [[Cat]]s have a significantly lower tolerance against benzoic acid and its [[Salt (chemistry)|salts]] than [[rat]]s and [[mouse|mice]]. Lethal dose for cats can be as low as 300 mg/kg body weight.<ref>{{cite journal| doi= 10.1136/vr.90.3.53|vauthors=Bedford PG, Clarke EG |title=Experimental benzoic acid poisoning in the cat|journal=Vet Rec |year=1972|pages=53–58|volume=90 |pmid = 4672555| issue= 3|doi-broken-date=11 July 2025 |s2cid=2553612 }}</ref> The oral {{LD50}} for rats is 3040 mg/kg, for mice it is 1940–2263 mg/kg.<ref name="concise" />
In [[Taipei]], Taiwan, a city health survey in 2010 found that 30% of dried and pickled food products had benzoic acid.<ref>{{cite news|first=Jian|last= Chen|author2=Y.L. Kao|url=http://www.chinapost.com.tw/taiwan/national/national-news/2010/01/18/241326/Nearly-30.htm |title=Nearly 30% dried, pickled foods fail safety inspections|newspaper=[[The China Post]]| date=18 January 2010}}</ref>
In [[Taipei]], Taiwan, a city health survey in 2010 found that 30% of dried and pickled food products had benzoic acid.<ref>{{cite news|first=Jian|last= Chen|author2=Y.L. Kao|url=http://www.chinapost.com.tw/taiwan/national/national-news/2010/01/18/241326/Nearly-30.htm |archive-url=https://web.archive.org/web/20110611235722/http://www.chinapost.com.tw/taiwan/national/national-news/2010/01/18/241326/Nearly-30.htm |url-status=dead |archive-date=11 June 2011 |title=Nearly 30% dried, pickled foods fail safety inspections|newspaper=[[The China Post]]| date=18 January 2010}}</ref>
Benzoic acid (/bɛnˈzoʊ.ɪk/) is a white or colorless crystalline organic compound with the formula C6H5COOH, whose structure consists of a benzene ring (C6H6) with a carboxyl (−C(=O)OH) substituent. The benzoyl group is often abbreviated "Bz" (not to be confused with "Bn", which is used for benzyl), thus benzoic acid is also denoted as BzOH, since the benzoyl group has the formula −C6H5CO. It is the simplest aromatic carboxylic acid. The name is derived from gum benzoin, which was for a long time its only source.
Benzoic acid occurs naturally in many plants[1] and serves as an intermediate in the biosynthesis of many secondary metabolites. Salts of benzoic acid are used as food preservatives. Benzoic acid is an important precursor for the industrial synthesis of many other organic substances. The salts and esters of benzoic acid are known as benzoates (/ˈbɛnzoʊ.eɪts/).
In 1875 Salkowski discovered the antifungal properties of benzoic acid, which explains the preservation of benzoate-containing cloudberry fruits.[4][5]
The process is catalyzed by cobalt or manganesenaphthenates. The process uses abundant materials and proceeds in high yield.[6]
The first industrial process involved the reaction of benzotrichloride (trichloromethyl benzene) with calcium hydroxide in water, using iron or iron salts as catalyst. The resulting calcium benzoate is converted to benzoic acid with hydrochloric acid. The product contains significant amounts of chlorinated benzoic acid derivatives. For this reason, benzoic acid for human consumption was obtained by dry distillation of gum benzoin. Food-grade benzoic acid is now produced synthetically.
Laboratory synthesis
Benzoic acid is cheap and readily available, so the laboratory synthesis of benzoic acid is mainly practiced for its pedagogical value. It is a common undergraduate preparation.
Benzoic acid can be purified by recrystallization from water because of its high solubility in hot water and poor solubility in cold water. The avoidance of organic solvents for the recrystallization makes this experiment particularly safe. This process usually gives a yield of around 65%.[7]
By hydrolysis
Like other nitriles and amides, benzonitrile and benzamide can be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions.
The temperature required can be lowered to 200 °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.
Typical 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.[18][19]
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.[20]
In teaching laboratories, benzoic acid is a common standard for calibrating a bomb calorimeter.[24]
Biology and health effects
Benzoic acid occurs naturally as do its esters in many plant and animal species. Appreciable amounts are found in most berries (around 0.05%). Ripe fruits of several Vaccinium species (e.g., cranberry, V. vitis macrocarpon; bilberry, V. myrtillus) contain as much as 0.03–0.13% free benzoic acid. Benzoic acid is also formed in apples after infection with the fungus Nectria galligena. Among animals, benzoic acid has been identified primarily in omnivorous or phytophageous species, e.g., in viscera and muscles of the rock ptarmigan (Lagopus muta) as well as in gland secretions of male muskoxen (Ovibos moschatus) or Asian bull elephants (Elephas maximus).[25]Gum benzoin contains up to 20% of benzoic acid and 40% benzoic acid esters.[26]
↑Donald L. Pavia (2004). Introduction to Organic Laboratory Techniques: A Small Scale Approach. Thomson Brooks/Cole. pp. 312–314. ISBN978-0-534-40833-6.
↑Shirley, D. A. (1954). "The Synthesis of Ketones from Acid Halides and Organometallic Compounds of Magnesium, Zinc, and Cadmium". Org. React.8: 28–58.
↑Santonastaso, Marco; Freakley, Simon J.; Miedziak, Peter J.; Brett, Gemma L.; Edwards, Jennifer K.; Hutchings, Graham J. (21 November 2014). "Oxidation of Benzyl Alcohol using in Situ Generated Hydrogen Peroxide". Organic Process Research & Development. 18 (11): 1455–1460. doi:10.1021/op500195e. ISSN1083-6160.
↑Pastrorova I, de Koster CG, Boom JJ (1997). "Analytic Study of Free and Ester Bound Benzoic and Cinnamic Acids of Gum Benzoin Resins by GC-MS HPLC-frit FAB-MS". Phytochem Anal. 8 (2): 63–73. doi:10.1002/(SICI)1099-1565(199703)8:2<63::AID-PCA337>3.0.CO;2-Y.
↑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 (inactive 11 July 2025). PMID4672555. S2CID2553612.CS1 maint: DOI inactive as of July 2025 (link)
