Difference between revisions of "Benzoic acid"
Physchim62 (talk | contribs) (Importing from http://en.wikipedia.org/w/index.php?title=Benzoic_acid&oldid=307133736) |
Physchim62 (talk | contribs) |
||
| (7 intermediate revisions by the same user not shown) | |||
| Line 1: | Line 1: | ||
| + | {{FixBunching|beg}} | ||
{{chembox | {{chembox | ||
| ImageFileL1 = Benzoic acid.svg | | ImageFileL1 = Benzoic acid.svg | ||
| Line 5: | Line 6: | ||
| ImageSizeR1 = 120px | | ImageSizeR1 = 120px | ||
| IUPACName = Benzoic acid | | IUPACName = Benzoic acid | ||
| − | | OtherNames = Benzenecarboxylic acid,<br/>Carboxybenzene,<br/>[[E210]], Dracylic acid | + | | OtherNames = Benzenecarboxylic acid,<br/>Carboxybenzene,<br/>[[E210]], Dracylic acid |
| Section1 = {{Chembox Identifiers | | Section1 = {{Chembox Identifiers | ||
| − | | | + | | InChI = 1/C7H6O2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9) |
| + | | StdInChI = 1S/C7H6O2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9) | ||
| + | | InChIKey = WPYMKLBDIGXBTP-UHFFFAOYAD | ||
| + | | StdInChIKey = WPYMKLBDIGXBTP-UHFFFAOYSA-N | ||
| CASNo = 65-85-0 | | CASNo = 65-85-0 | ||
| CASNo_Ref = {{cascite}} | | CASNo_Ref = {{cascite}} | ||
| Line 14: | Line 18: | ||
| ChemSpiderID= 238 | | ChemSpiderID= 238 | ||
| SMILES = c1ccccc1C(=O)O | | SMILES = c1ccccc1C(=O)O | ||
| − | |||
| RTECS = DG0875000 | | RTECS = DG0875000 | ||
| − | + | }} | |
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| Section2 = {{Chembox Properties | | Section2 = {{Chembox Properties | ||
| + | | Reference = <ref name="ICSC">{{ICSC-ref|0103|name=Benzoic acid|date=October 1999}}.</ref><ref>{{citation | url = http://oru.edu/cccda/sl/solubility/allsolvents.php?solute=benzoic%20acid | webpage = Solubility of benzoic acid in non-aqueous solvents}}.</ref> | ||
| Formula = C<sub>6</sub>H<sub>5</sub>COOH | | Formula = C<sub>6</sub>H<sub>5</sub>COOH | ||
| MolarMass = 122.12 g/mol | | MolarMass = 122.12 g/mol | ||
| Line 32: | Line 27: | ||
| Density = 1.32 g/cm<sup>3</sup>, solid | | Density = 1.32 g/cm<sup>3</sup>, solid | ||
| MeltingPt = 122.4 °C (395 K) | | MeltingPt = 122.4 °C (395 K) | ||
| − | + | | BoilingPt = 249 °C (522 K) | |
| − | | BoilingPt = 249 | + | | Solubility = Soluble (hot water)<br/>0.29 g/100 ml (20 °C) |
| − | + | | Solubility2 = 3.37 mol/dm<sup>3</sup> | |
| − | | Solubility = Soluble (hot water)<br/> | + | | Solvent2 = [[THF]] |
| − | | | + | | Solubility3 = 2.52 mol/dm<sup>3</sup> |
| − | | | + | | Solvent3 = [[ethanol]] |
| + | | Solubility4 = 2.82 mol/dm<sup>3</sup> | ||
| + | | Solvent4 = [[methanol]] | ||
| pKa = 4.21 | | pKa = 4.21 | ||
| − | | | + | | Dipole = 1.72 D ([[dioxane]] soln.) |
| − | + | | LogP = 1.87 | |
| − | |||
| − | |||
| − | |||
| − | | | ||
| − | |||
| − | |||
}} | }} | ||
| Section3 = {{Chembox Structure | | Section3 = {{Chembox Structure | ||
| CrystalStruct = [[Monoclinic]] | | CrystalStruct = [[Monoclinic]] | ||
| − | |||
| MolShape = [[planar]] | | MolShape = [[planar]] | ||
| − | + | }} | |
| − | |||
| Section4 = {{Chembox Thermochemistry | | Section4 = {{Chembox Thermochemistry | ||
| − | | | + | | Reference = <ref>{{NIST chemistry|id=1S/C7H6O2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9)|name=Benzoic acid|accessdate=2009-08-22}}.</ref> |
| − | + | | DeltaHf = –385 kJ/mol | |
| − | + | | DeltaHc = –3228±4 kJ/mol | |
| − | + | | Entropy = 167.2 J K<sup>–1</sup> mol<sup>–1</sup> | |
| − | + | }} | |
| − | |||
| − | | | ||
| − | | | ||
| − | | | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | | | ||
| − | | | ||
| − | | | ||
| − | |||
| − | |||
| Section7 = {{Chembox Hazards | | Section7 = {{Chembox Hazards | ||
| − | | | + | | Reference = <ref name="ICSC"/><ref>{{GHS class NZ|id=5014|accessdate=2009-08-22}}.</ref> |
| − | | | + | | ExternalMSDS = {{ICSC-small|0103}} |
| EUIndex = not listed | | EUIndex = not listed | ||
| − | | | + | | GHSPictograms = {{GHS exclamation mark|Acute Tox. (oral) 4; Eye Irrit. 2}}{{GHS health hazard|STOT RE (inhalation) 2}} |
| − | | | + | | GHSSignalWord = WARNING |
| − | | | + | | HPhrases = {{H-phrases|302|319|373}} |
| − | | | + | | FlashPt = 121 °C (250 ºF) |
| − | + | | Autoignition = 570 ºC (1058 ºF) | |
| − | | | + | }} |
| − | | | ||
| − | | | ||
| − | | FlashPt = 121 °C ( | ||
| − | | Autoignition = | ||
| − | |||
| − | |||
| − | |||
| Section8 = {{Chembox Related | | Section8 = {{Chembox Related | ||
| − | + | | OtherFunctn = [[Phenylacetic acid]]<br/>[[Hippuric acid]]<br/>[[Salicylic acid]] | |
| − | |||
| − | | OtherFunctn = [[ | ||
| Function = [[carboxylic acid]]s | | Function = [[carboxylic acid]]s | ||
| − | | OtherCpds = [[ | + | | OtherCpds = [[Benzene]]<br/>[[Benzaldehyde]]<br/>[[Benzyl alcohol]]<br/>[[Benzylamine]]<br/>[[Benzyl benzoate]]<br/>[[Benzoyl chloride]] |
| − | + | }} | |
}} | }} | ||
| + | {{FixBunching|mid}} | ||
[[Image:S-Sci-ArCOOH.jpg|right|thumb|300px|Benzoic Acid Crystals]] | [[Image:S-Sci-ArCOOH.jpg|right|thumb|300px|Benzoic Acid Crystals]] | ||
| − | + | {{FixBunching|end}} | |
'''Benzoic acid''', C<sub>7</sub>H<sub>6</sub>O<sub>2</sub> (or C<sub>6</sub>H<sub>5</sub>COOH), is a colorless crystalline solid and the simplest [[aromatic]] [[carboxylic acid]]. The name derived from [[gum benzoin]], which was for a long time the only source for benzoic acid. This weak acid and its salts are used as a food preservative. Benzoic acid is an important precursor for the synthesis of many other organic substances. | '''Benzoic acid''', C<sub>7</sub>H<sub>6</sub>O<sub>2</sub> (or C<sub>6</sub>H<sub>5</sub>COOH), is a colorless crystalline solid and the simplest [[aromatic]] [[carboxylic acid]]. The name derived from [[gum benzoin]], which was for a long time the only source for benzoic acid. This weak acid and its salts are used as a food preservative. Benzoic acid is an important precursor for the synthesis of many other organic substances. | ||
== History == | == History == | ||
| + | Benzoic acid was discovered in the 16th century. The [[dry distillation]] of [[gum benzoin]] first described by [[Nostradamus]] (1556), and subsequently by [[Alexius Pedemontanus]] (1560) and [[Blaise de Vigenère]] (1596).<ref>{{citation | last = Neumüller | first = O.-A. | year = 1988 | title = Römpps Chemie-Lexikon | edition = 6th | publisher = Frankh'sche Verlagshandlung | location = Stuttgart| isbn = 3-440-04516-1 | oclc= 50969944}}.</ref> | ||
| − | + | [[Justus von Liebig]] and [[Friedrich Wöhler]] determined the structure of benzoic acid in 1832.<ref>{{citation | authorlink1 = Justus von Liebig | last1 = Liebig | first1 = J. | authorlink2 = Friedrich Wöhler | last2 = Wöhler | first2 = F. | title = Untersuchungen über das Radikal der Benzoesäure | journal = Ann. Chem. | year = 1832 | volume = 3 | pages = 249–82 | doi = 10.1002/jlac.18320030302}}.</ref> They also investigated how [[hippuric acid]] is related to benzoic acid. | |
| − | |||
| − | [[Justus von Liebig]] and [[Friedrich Wöhler]] determined the structure of benzoic acid in 1832.<ref>{{ | ||
| − | | | ||
| − | | title=Untersuchungen über das Radikal der Benzoesäure | ||
| − | | journal = | ||
| − | | year = 1832 | ||
| − | | volume = 3 | ||
| − | | pages = | ||
| − | | doi = 10.1002/jlac.18320030302}}</ref> They also investigated how [[hippuric acid]] is related to benzoic acid. | ||
| − | In 1875 Salkowski discovered the [[antifungal]] abilities of benzoic acid, which was used for a long time in the preservation of benzoate-containing [[Cloudberry|cloudberry fruits]].<ref>{{ | + | In 1875 Salkowski discovered the [[antifungal]] abilities of benzoic acid, which was used for a long time in the preservation of benzoate-containing [[Cloudberry|cloudberry fruits]].<ref>{{citation | last = Salkowski | first = E. | journal = Berl. Klin. Wochenschr. | year = 1875 | volume = 12 | pages = 297–98}}.</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 cheap raw materials, proceeds in high yield, and is considered environmentally green.{{Citation needed|date=July 2009}} | 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 cheap raw materials, proceeds in high yield, and is considered environmentally green.{{Citation needed|date=July 2009}} | ||
| + | [[Image:Benzoic acid-chemical-synthesis-1.png|220px|toluene oxidation]] | ||
| − | + | U.S. production capacity is estimated to be 126,000 [[tonne]]s per year, much of which is consumed domestically to prepare other industrial chemicals. | |
| − | |||
| − | U.S. production capacity is estimated to be 126,000 [[tonne]]s per year | ||
=== Laboratory synthesis === | === 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 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. | ||
| − | For all syntheses, 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. Other possible recrystallization solvents include [[acetic acid]] ([[anhydrous]] or aqueous), [[benzene]], petroleum ether, and a mixture of ethanol and water.<ref>{{ | + | For all syntheses, 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. Other possible recrystallization solvents include [[acetic acid]] ([[anhydrous]] or aqueous), [[benzene]], petroleum ether, and a mixture of ethanol and water.<ref>{{citation | title = Purification of Laboratory Chemicals | edition = 3rd | first1 = D. D. | last1 = Perrin | first2 = W. L. F. | last2 = Armarego | publisher = Pergamon | page = 94 | year = 1988 | isbn = 0-08-034715-0}}.</ref> |
==== By hydrolysis ==== | ==== By hydrolysis ==== | ||
| − | |||
Like any other [[nitrile]] or [[amide]], [[benzonitrile]] and [[benzamide]] can be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions. | Like any other [[nitrile]] or [[amide]], [[benzonitrile]] and [[benzamide]] can be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions. | ||
==== From benzaldehyde ==== | ==== From benzaldehyde ==== | ||
| − | |||
The base-induced [[disproportionation]] of [[benzaldehyde]], the [[Cannizzaro reaction]], affords equal amounts of benzoate and [[benzyl alcohol]]; the latter can be removed by [[distillation]]. | The base-induced [[disproportionation]] of [[benzaldehyde]], the [[Cannizzaro reaction]], affords equal amounts of benzoate and [[benzyl alcohol]]; the latter can be removed by [[distillation]]. | ||
| Line 152: | Line 98: | ||
==== From bromobenzene ==== | ==== From bromobenzene ==== | ||
| − | + | [[Bromobenzene]] can be converted to benzoic acid by "carbonation" of the intermediate [[phenylmagnesium bromide]]:<ref>{{citation | title = Introduction to Organic Laboratory Techniques: A Small Scale Approach | first = Donald L. | last = Pavia | year = 2004 | publisher = Thomson Brooks/Cole | isbn = 0534408338 | pages = 312–14}}.</ref> | |
| − | [[Bromobenzene]] can be converted to benzoic acid by "carbonation" of the intermediate [[phenylmagnesium bromide]]:<ref>{{ | ||
:C<sub>6</sub>H<sub>5</sub>MgBr + CO<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>CO<sub>2</sub>MgBr | :C<sub>6</sub>H<sub>5</sub>MgBr + CO<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>CO<sub>2</sub>MgBr | ||
| Line 159: | Line 104: | ||
==== From benzyl alcohol ==== | ==== From benzyl alcohol ==== | ||
| − | |||
[[Benzyl alcohol]] is refluxed with potassium permanganate or other oxidizing reagents in water. The mixture is hot filtered to remove manganese dioxide and then allowed to cool to afford benzoic acid. | [[Benzyl alcohol]] is refluxed with potassium permanganate or other oxidizing reagents in water. The mixture is hot filtered to remove manganese dioxide and then allowed to cool to afford benzoic acid. | ||
=== Historical preparations === | === Historical preparations === | ||
| + | The first industrial process involved the reaction of [[benzotrichloride]] (trichloromethyl benzene) with [[calcium hydroxide]] in water, using [[iron]] or iron salts as a [[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.<ref>{{citation | url = http://www.columbian.com/lifeHome/whatsinmy/10102006news66192.cfm | webpage = What's in my... | accessdate = 2007-09-08 | last = Killinger-Mann | first = Karen | date = 2007-09-07}}.</ref> | ||
| − | + | [[Alkyl]]-substituted [[benzene]] derivatives give benzoic acid with the stoichiometric oxidants [[potassium permanganate]], [[chromium trioxide]], [[nitric acid]]. | |
| − | |||
| − | |||
== Uses == | == Uses == | ||
| Line 173: | Line 116: | ||
*[[Benzoyl chloride]], C<sub>6</sub>H<sub>5</sub>C(O)Cl, is obtained by treatment of benzoic with [[thionyl chloride]], [[phosgene]] or one of the [[phosphorus chlorides|chlorides of phosphorus]]. C<sub>6</sub>H<sub>5</sub>C(O)Cl is an important starting material for several benzoic acid derivates like [[benzyl benzoate]], which is used in [[Flavouring|artificial flavours]] and [[insect repellent]]s. | *[[Benzoyl chloride]], C<sub>6</sub>H<sub>5</sub>C(O)Cl, is obtained by treatment of benzoic with [[thionyl chloride]], [[phosgene]] or one of the [[phosphorus chlorides|chlorides of phosphorus]]. C<sub>6</sub>H<sub>5</sub>C(O)Cl is an important starting material for several benzoic acid derivates like [[benzyl benzoate]], which is used in [[Flavouring|artificial flavours]] and [[insect repellent]]s. | ||
*Benzoate [[plasticizer]]s, such as the glycol-, diethylengylcol-, and triethyleneglycol esters, are obtained by [[transesterification]] of [[methyl benzoate]] with the corresponding [[diol]]. Alternatively these species arise by treatment of benzoylchloride with the diol. These plasticizers are used similarly to those derived from terephthalic acid ester. | *Benzoate [[plasticizer]]s, such as the glycol-, diethylengylcol-, and triethyleneglycol esters, are obtained by [[transesterification]] of [[methyl benzoate]] with the corresponding [[diol]]. Alternatively these species arise by treatment of benzoylchloride with the diol. These plasticizers are used similarly to those derived from terephthalic acid ester. | ||
| − | *[[Phenol]], C<sub>6</sub>H<sub>5</sub>OH, is obtained by oxidative [[decarboxylation]] at 300- | + | *[[Phenol]], C<sub>6</sub>H<sub>5</sub>OH, is obtained by oxidative [[decarboxylation]] at 300-400 °C. The temperature required can be lowered to 200 °C by the addition of catalytic amounts of [[copper|copper(II) salts]]. The phenol can be converted to [[cyclohexanol]], which is a starting material for [[nylon]] synthesis. |
=== Food preservative === | === Food preservative === | ||
| + | Benzoic acid and its salts are used as a food [[preservative]], represented by the [[E-numbers]] [[E210]], [[sodium benzoate|E211]], [[potassium benzoate|E212]], and [[calcium benzoate|E213]]. Benzoic acid inhibits the growth of [[mold]], [[yeast]]<ref>{{citation | first = A. D. | last = 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. | year = 1991 | url = http://aem.asm.org/cgi/content/abstract/57/12/3410 | volume = 1 | pages = 1 | pmid = 1785916}}.</ref> and some [[bacterium|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 in to 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>{{citation | last1 = Pastrorova | first1 = I. | last2 = de Koster | first2 = C. G. | last3 = Boom | first3 = J. J. | 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}}.</ref> Acidic food and beverage like [[fruit juice]] ([[citric acid]]), sparkling drinks ([[carbon dioxide]]), [[soft drinks]] ([[phosphoric acid]]), [[Pickling|pickles]] ([[vinegar]]) or other acidified food are preserved with benzoic acid and benzoates. | ||
| − | + | Typical levels of use for benzoic acid as a preservative in food are between 0.05–0.1%. Foods in which benzoic acid may be used and maximum levels for its application are laid down in international food law.<ref>{{citation | url = http://www.codexalimentarius.net/gsfaonline/groups/details.html?id=162 | webpage = GSFA Online Food Additive Group Details: Benzoates (2006)}}.</ref><ref>[http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31995L0002:EN:HTML European Parliament and Council Directive No 95/2/EC of 20 February 1995 on food additives other than colours and sweeteners]. ''OJEU'' L61, 18.3.1995, pp 1–40.</ref> | |
| − | |||
| − | Typical levels of use for benzoic acid as a preservative in food are between 0. | ||
| − | 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 [[benzene]].<ref>http://www.bfr.bund.de/cm/245/indications_of_the_possible_formation_of_benzene_from_benzoic_acid_in_foods.pdf BfR article</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 [[benzene]].<ref>{{citation | url =http://www.bfr.bund.de/cm/245/indications_of_the_possible_formation_of_benzene_from_benzoic_acid_in_foods.pdf | webpage = BfR article}}.</ref> |
{{See also|Benzene in soft drinks}} | {{See also|Benzene in soft drinks}} | ||
=== Medicinal === | === Medicinal === | ||
| − | |||
Benzoic acid is a constituent of [[Whitfield's Ointment]] which is used for the treatment of fungal skin diseases such as tinea, [[ringworm]], and [[athlete's foot]]. | Benzoic acid is a constituent of [[Whitfield's Ointment]] which is used for the treatment of fungal skin diseases such as tinea, [[ringworm]], and [[athlete's foot]]. | ||
| − | <ref> | + | <ref>{{citation | url = http://www.medipharmalimited.com/whitfield_ointment.asp | webpage = Whitfield Ointment}}.</ref><ref>{{citation | title = Wilson and Gisvold's Textbook of Organic Medicinal and Pharmaceutical | first1 = Charles | last1 = Owens Wilson | first2 = Ole | last2 = Gisvold | first3 = John H. | last3 = Block | year = 2004 | publisher = Lippincott Williams & Wilkins | isbn = 0781734819 | page = 234}}.</ref> |
== Biology and health effects == | == Biology and health effects == | ||
| − | |||
Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Appreciable amounts have been found in most berries (around 0.05%). Ripe fruits of several ''[[Vaccinium]]'' species (e.g., [[cranberry]], ''V. vitis idaea''; [[bilberry]], ''V. macrocarpon'') contain as much as 300-1300 mg free benzoic acid per kg fruit. Benzoic acid is also formed in [[apple]]s after infection with the fungus ''[[Nectria galligena]]''. | Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Appreciable amounts have been found in most berries (around 0.05%). Ripe fruits of several ''[[Vaccinium]]'' species (e.g., [[cranberry]], ''V. vitis idaea''; [[bilberry]], ''V. macrocarpon'') contain as much as 300-1300 mg free benzoic acid per kg fruit. Benzoic acid is also formed in [[apple]]s 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 [[ptarmigan]] (''Lagopus mutus'') as well as in gland secretions of male [[muskoxen]] (''Ovibos moschatus'') or Asian bull elephants (''[[Elephas maximus]]'').<ref name = " | + | Among animals, benzoic acid has been identified primarily in omnivorous or phytophageous species, e.g., in viscera and muscles of the [[ptarmigan]] (''Lagopus mutus'') as well as in gland secretions of male [[muskoxen]] (''Ovibos moschatus'') or Asian bull elephants (''[[Elephas maximus]]'').<ref name="CICAD">{{CICAD-ref | number = 26 | name = Benzoic Acid and Sodium Benzoate | year = 2000 | isbn=92-4-153026-X}}.</ref> |
| − | [[Gum benzoin]] contains up to 20% of benzoic acid and 40% benzoic acid esters.<ref>{{ | + | [[Gum benzoin]] contains up to 20% of benzoic acid and 40% benzoic acid esters.<ref>{{citation | last1 = Tomokuni | first1 = K. | last2 = Ogata | first2 = M. | title = Direct Colorimetric Determination of Hippuric Acid in Urine | journal = Clin. Chem. | year = 1972 | pages = 349–51 | volume = 18}}.</ref> |
| − | Benzoic acid is present as part of [[hippuric acid]] (N- | + | Benzoic acid is present as part of [[hippuric acid]] (''N''-benzoylglycine) in [[urine]] of [[mammals]], especially [[herbivores]] (Gr. ''hippos'' = horse; ''ouron'' = urine). Humans produce about 0.44 g/L [[hippuric acid]] per day in their urine, and if the person is exposed to [[toluene]] or benzoic acid it can rise above that level.<ref>{{citation | last1 = Krebs | first1 = Hans A. | last2 = Wiggins | first2 = David | last3 = Stubbs | first3 = Marion | first4 = Alberto | last4 = Sols | first5 = Francisco | last5 = Bedoya | title = Studies on the mechanism of the antifungal action of benzoate | journal = Biochem. J. | year = 1983 | volume = 214 | pages = 657–63 | url = http://www.biochemj.org/bj/214/0657/2140657.pdf}}.</ref> |
| − | For humans, the WHO's International Programme on Chemical Safety (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.<ref name=" | + | For humans, the WHO's International Programme on Chemical Safety (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.<ref name="CICAD"/> [[Cat]]s have a significantly lower tolerance against benzoic acid and its [[salt]]s than [[rat]]s and [[mouse|mice]]. Lethal dose for cats can be as low as 300 mg/kg body weight.<ref>{{citation | last1 = Bedford | first1 = P. G. | last2 = Clarke | first2 = E. G. | title = Experimental benzoic acid poisoning in the cat | journal = Vet. Rec. | year = 1972 | pages = 53–58 | volume = 90 | pmid = 4672555}}.</ref> The oral [[LD50|LD<sub>50</sub>]] for rats is 3040 mg/kg, for mice it is 1940-2263 mg/kg.<ref name="CICAD"/> |
== Chemistry == | == Chemistry == | ||
| − | |||
Reactions of benzoic acid can occur at either the [[aromaticity|aromatic ring]] or the [[carboxyl group]]: | Reactions of benzoic acid can occur at either the [[aromaticity|aromatic ring]] or the [[carboxyl group]]: | ||
| Line 210: | Line 149: | ||
[[Electrophilic aromatic substitution]] reaction will take place mainly in 3-position due to the [[deactivating group|electron-withdrawing]] [[carboxylic group]]; i.e. benzoic acid is [[electrophilic aromatic substitution#Meta directors|''meta'' directing]]. | [[Electrophilic aromatic substitution]] reaction will take place mainly in 3-position due to the [[deactivating group|electron-withdrawing]] [[carboxylic group]]; i.e. benzoic acid is [[electrophilic aromatic substitution#Meta directors|''meta'' directing]]. | ||
| − | The second substitution reaction (on the right) is slower because the first nitro group is deactivating.<ref>{{OrgSynth | | + | The second substitution reaction (on the right) is slower because the first nitro group is deactivating.<ref>{{OrgSynth | last1 = Brewster | first1 = R. Q. | last2 = Williams | first2 = Bill | last3 = Phillips | first3 = Ross | title = 3,5-Dinitrobenzoic Acid | prep = cv3p0337 | volume = 22 | page = 48 | collvol = 3 | collvolpages = 337 | year= 1942}}.</ref> Conversely, if an activating group (electron-donating) was introduced (e.g., alkyl), a second substitution reaction would occur more readily than the first and the disubstituted product might not accumulate to a significant extent. |
=== Carboxyl group === | === Carboxyl group === | ||
| − | |||
All the reactions mentioned for [[carboxylic acid]]s are also possible for benzoic acid. | All the reactions mentioned for [[carboxylic acid]]s are also possible for benzoic acid. | ||
| − | |||
* Benzoic acid [[esters]] are the product of the acid catalysed reaction with [[alcohols]]. | * Benzoic acid [[esters]] are the product of the acid catalysed reaction with [[alcohols]]. | ||
* Benzoic acid [[amide]]s are more easily available by using activated acid derivatives (such as [[benzoyl chloride]]) or by coupling reagents used in [[peptide synthesis]] like [[Dicyclohexylcarbodiimide|DCC]] and [[DMAP]]. | * Benzoic acid [[amide]]s are more easily available by using activated acid derivatives (such as [[benzoyl chloride]]) or by coupling reagents used in [[peptide synthesis]] like [[Dicyclohexylcarbodiimide|DCC]] and [[DMAP]]. | ||
| Line 227: | Line 164: | ||
== References == | == References == | ||
| − | {{ | + | {{reflist}} |
== Further reading == | == Further reading == | ||
| − | + | *{{citation | title = Final Report on the Safety Assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate | journal = Int. J. Toxicol. | year = 2001 | volume = 20 | issue = Suppl. 3 | pages = 23–50 | doi = 10.1080/10915810152630729 | pmid = 11766131}}. | |
| − | * {{ | ||
== External links == | == External links == | ||
| − | * | + | *{{ICSC|0103}} |
| − | * | + | *{{CICAD|number=26|name=Benzoic Acid and Sodium Benzoate}} |
| + | *{{SIDS|name=Benzoic Acid|id=BENZOATES}} | ||
[[Category:Carboxylic acids]] | [[Category:Carboxylic acids]] | ||
Latest revision as of 08:01, 1 September 2009
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Benzoic acid, C7H6O2 (or C6H5COOH), is a colorless crystalline solid and the simplest aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. This weak acid and its salts are used as a food preservative. Benzoic acid is an important precursor for the synthesis of many other organic substances.
Contents
History
Benzoic acid was discovered in the 16th century. The dry distillation of gum benzoin first described by Nostradamus (1556), and subsequently by Alexius Pedemontanus (1560) and Blaise de Vigenère (1596).[5]
Justus von Liebig and Friedrich Wöhler determined the structure of benzoic acid in 1832.[6] They also investigated how hippuric acid is related to benzoic acid.
In 1875 Salkowski discovered the antifungal abilities of benzoic acid, which was used for a long time in the preservation of benzoate-containing cloudberry fruits.[7]
Production
Industrial preparations
Benzoic acid is produced commercially by partial oxidation of toluene with oxygen. The process is catalyzed by cobalt or manganese naphthenates. The process uses cheap raw materials, proceeds in high yield, and is considered environmentally green.[ref. needed]
U.S. production capacity is estimated to be 126,000 tonnes per year, much of which is consumed domestically to prepare other industrial chemicals.
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.
For all syntheses, 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. Other possible recrystallization solvents include acetic acid (anhydrous or aqueous), benzene, petroleum ether, and a mixture of ethanol and water.[8]
By hydrolysis
Like any other nitrile or amide, benzonitrile and benzamide can be hydrolyzed to benzoic acid or its conjugate base in acid or basic conditions.
From benzaldehyde
The base-induced disproportionation of benzaldehyde, the Cannizzaro reaction, affords equal amounts of benzoate and benzyl alcohol; the latter can be removed by distillation.
From bromobenzene
Bromobenzene can be converted to benzoic acid by "carbonation" of the intermediate phenylmagnesium bromide:[9]
- C6H5MgBr + CO2 → C6H5CO2MgBr
- C6H5CO2MgBr + HCl → C6H5CO2H + MgBrCl
From benzyl alcohol
Benzyl alcohol is refluxed with potassium permanganate or other oxidizing reagents in water. The mixture is hot filtered to remove manganese dioxide and then allowed to cool to afford benzoic acid.
Historical preparations
The first industrial process involved the reaction of benzotrichloride (trichloromethyl benzene) with calcium hydroxide in water, using iron or iron salts as a 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.[10]
Alkyl-substituted benzene derivatives give benzoic acid with the stoichiometric oxidants potassium permanganate, chromium trioxide, nitric acid.
Uses
Feedstock
Benzoic acid is used to make a large number of chemicals, important examples of which are:
- Benzoyl chloride, C6H5C(O)Cl, is obtained by treatment of benzoic with thionyl chloride, phosgene or one of the chlorides of phosphorus. C6H5C(O)Cl is an important starting material for several benzoic acid derivates like benzyl benzoate, which is used in artificial flavours and insect repellents.
- Benzoate plasticizers, such as the glycol-, diethylengylcol-, and triethyleneglycol esters, are obtained by transesterification of methyl benzoate with the corresponding diol. Alternatively these species arise by treatment of benzoylchloride with the diol. These plasticizers are used similarly to those derived from terephthalic acid ester.
- Phenol, C6H5OH, is obtained by oxidative decarboxylation at 300-400 °C. 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.
Food preservative
Benzoic acid and its salts are used as a food preservative, represented by the E-numbers E210, E211, E212, and E213. Benzoic acid inhibits the growth of mold, yeast[11] 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 in to the cell. If the intracellular pH changes to 5 or lower, the 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.[12] Acidic food and beverage like fruit juice (citric acid), sparkling drinks (carbon dioxide), soft drinks (phosphoric acid), pickles (vinegar) or other acidified food are preserved with benzoic acid and benzoates.
Typical levels of use for benzoic acid as a preservative in food are between 0.05–0.1%. Foods in which benzoic acid may be used and maximum levels for its application are laid down in international food law.[13][14]
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 benzene.[15]
- 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 tinea, ringworm, and athlete's foot. [16][17]
Biology and health effects
Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Appreciable amounts have been found in most berries (around 0.05%). Ripe fruits of several Vaccinium species (e.g., cranberry, V. vitis idaea; bilberry, V. macrocarpon) contain as much as 300-1300 mg free benzoic acid per kg fruit. 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 ptarmigan (Lagopus mutus) as well as in gland secretions of male muskoxen (Ovibos moschatus) or Asian bull elephants (Elephas maximus).[18]
Gum benzoin contains up to 20% of benzoic acid and 40% benzoic acid esters.[19]
Benzoic acid is present as part of hippuric acid (N-benzoylglycine) in urine of mammals, especially herbivores (Gr. hippos = horse; ouron = urine). Humans produce about 0.44 g/L hippuric acid per day in their urine, and if the person is exposed to toluene or benzoic acid it can rise above that level.[20]
For humans, the WHO's International Programme on Chemical Safety (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.[18] Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice. Lethal dose for cats can be as low as 300 mg/kg body weight.[21] The oral LD50 for rats is 3040 mg/kg, for mice it is 1940-2263 mg/kg.[18]
Chemistry
Reactions of benzoic acid can occur at either the aromatic ring or the carboxyl group:
Aromatic ring
Electrophilic aromatic substitution reaction will take place mainly in 3-position due to the electron-withdrawing carboxylic group; i.e. benzoic acid is meta directing.
The second substitution reaction (on the right) is slower because the first nitro group is deactivating.[22] Conversely, if an activating group (electron-donating) was introduced (e.g., alkyl), a second substitution reaction would occur more readily than the first and the disubstituted product might not accumulate to a significant extent.
Carboxyl group
All the reactions mentioned for carboxylic acids are also possible for benzoic acid.
- Benzoic acid esters are the product of the acid catalysed reaction with alcohols.
- Benzoic acid amides are more easily available by using activated acid derivatives (such as benzoyl chloride) or by coupling reagents used in peptide synthesis like DCC and DMAP.
- The more active benzoic anhydride is formed by dehydration using acetic anhydride or phosphorus pentoxide.
- Highly reactive acid derivatives such as acid halides are easily obtained by mixing with halogenation agents like phosphorus chlorides or thionyl chloride.
- Orthoesters can be obtained by the reaction of alcohols under acidic water free conditions with benzonitrile.
- Reduction to benzaldehyde and benzyl alcohol is possible using DIBAL-H, LiAlH4 or sodium borohydride.
- The copper catalysed decarboxylation of benzoate to benzene may be effected by heating in quinoline. Also, Hunsdiecker decarboxylation can be achieved by forming the silver salt and heating.
References
- ↑ 1.0 1.1 Benzoic acid; International Chemical Safety Card 0103; International Labour Organization: Geneva, October 1999, <http://www.inchem.org/documents/icsc/icsc/eics0103.htm>.
- ↑ Solubility of benzoic acid in non-aqueous solvents, <http://oru.edu/cccda/sl/solubility/allsolvents.php?solute=benzoic%20acid>.
- ↑ Benzoic acid. In NIST Chemistry WebBook; National Institute for Standards and Technology, <http://webbook.nist.gov/cgi/inchi/InChI%3D1S/C7H6O2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9)>. (accessed 22 August 2009).
- ↑ HSNO Chemical Classification Information Database, <http://www.ermanz.govt.nz/Chemicals/ChemicalDisplay.aspx?SubstanceID=5014> (accessed 22 August 2009), New Zealand Environmental Risk Management Authority.
- ↑ Neumüller, O.-A. Römpps Chemie-Lexikon, 6th ed.; Frankh'sche Verlagshandlung: Stuttgart, 1988. ISBN 3-440-04516-1. OCLC 50969944.
- ↑ Liebig, J.; Wöhler, F. Untersuchungen über das Radikal der Benzoesäure. Ann. Chem. 1832, 3, 249–82. DOI: 10.1002/jlac.18320030302.
- ↑ Salkowski, E. Berl. Klin. Wochenschr. 1875, 12, 297–98.
- ↑ Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon, 1988; p 94. ISBN 0-08-034715-0.
- ↑ Pavia, Donald L. Introduction to Organic Laboratory Techniques: A Small Scale Approach; Thomson Brooks/Cole, 2004; pp 312–14. ISBN 0534408338.
- ↑ Killinger-Mann, Karen What's in my..., <http://www.columbian.com/lifeHome/whatsinmy/10102006news66192.cfm> (accessed 8 September 2007).
- ↑ Warth, A. D. Mechanism of action of benzoic acid on Zygosaccharomyces bailii: effects on glycolytic metabolite levels, energy production, and intracellular pH. Appl. Environ. Microbiol. 1991, 1, 1. PMID 1785916, <http://aem.asm.org/cgi/content/abstract/57/12/3410>.
- ↑ Pastrorova, I.; de Koster, C. G.; Boom, J. J. Analytic Study of Free and Ester Bound Benzoic and Cinnamic Acids of Gum Benzoin Resins by GC-MS HPLC-frit FAB-MS. Phytochem. Anal. 1997, 8, 63–73. DOI: 10.1002/(SICI)1099-1565(199703)8:2<63::AID-PCA337>3.0.CO;2-Y.
- ↑ GSFA Online Food Additive Group Details: Benzoates (2006), <http://www.codexalimentarius.net/gsfaonline/groups/details.html?id=162>.
- ↑ European Parliament and Council Directive No 95/2/EC of 20 February 1995 on food additives other than colours and sweeteners. OJEU L61, 18.3.1995, pp 1–40.
- ↑ BfR article, <http://www.bfr.bund.de/cm/245/indications_of_the_possible_formation_of_benzene_from_benzoic_acid_in_foods.pdf>.
- ↑ Whitfield Ointment, <http://www.medipharmalimited.com/whitfield_ointment.asp>.
- ↑ Owens Wilson, Charles; Gisvold, Ole; Block, John H. Wilson and Gisvold's Textbook of Organic Medicinal and Pharmaceutical; Lippincott Williams & Wilkins, 2004; p 234. ISBN 0781734819.
- ↑ 18.0 18.1 18.2 Benzoic Acid and Sodium Benzoate; Concise International Chemical Assessment Document No. 26; International Programme on Chemical Safety: Geneva, 2000. ISBN 92-4-153026-X, <http://www.inchem.org/documents/cicads/cicads/cicad26.htm>.
- ↑ Tomokuni, K.; Ogata, M. Direct Colorimetric Determination of Hippuric Acid in Urine. Clin. Chem. 1972, 18, 349–51.
- ↑ Krebs, Hans A.; Wiggins, David; Stubbs, Marion; Sols, Alberto; Bedoya, Francisco Studies on the mechanism of the antifungal action of benzoate. Biochem. J. 1983, 214, 657–63, <http://www.biochemj.org/bj/214/0657/2140657.pdf>.
- ↑ Bedford, P. G.; Clarke, E. G. Experimental benzoic acid poisoning in the cat. Vet. Rec. 1972, 90, 53–58. PMID 4672555.
- ↑ Brewster, R. Q.; Williams, Bill; Phillips, Ross 3,5-Dinitrobenzoic Acid. Org. Synth. 1942, 22, 48, <http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv3p0337>; Coll. Vol., 3, 337.
Further reading
- Final Report on the Safety Assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate. Int. J. Toxicol. 2001, 20 (Suppl. 3), 23–50. PMID 11766131. DOI: 10.1080/10915810152630729.
External links
- International Chemical Safety Card 0103
- IPCS Concise International Chemical Assessment Document 26: Benzoic Acid and Sodium Benzoate
- SIDS Initial Assessment Report for Benzoic Acid from the Organisation for Economic Co-operation and Development (OECD)
| Error creating thumbnail: Unable to save thumbnail to destination |  |
This page was originally imported from Wikipedia, specifically this version of the article "Benzoic acid". Please see the history page on Wikipedia for the original authors. This WikiChem article may have been modified since it was imported. It is licensed under the Creative Commons Attribution–Share Alike 3.0 Unported license. |
