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Benzoic acid

Benzoic acid crystals IUPAC name[hide] Benzoic acid Other names[hide] Carboxybenzene; E210; Dracylic acid Identifiers CAS number 65-85-0 PubChem 243 ChemSpider 238 UNII 8SKN0B0MIM EC number 200-618-2 DrugBank DB03793 KEGG D00038 MeSH benzoic+acid ChEBI CHEBI:30746 ChEMBL CHEMBL541 RTECS number DG0875000 Beilstein Reference 636131

Gmelin Reference 3DMet Jmol-3D images

2946 B00053 Image 1 Image 2 SMILES

[show] InChI [show] Molecular formula Molar mass Appearance Density Melting point Boiling point Solubility in water Acidity (pKa) Refractive index (nD) Crystal structure Molecular shape Dipole moment MSDS EU Index Main hazards

NFPA 704

Flash point Autoignition temperature

Properties C7H6O2 122.12 g mol−1 Colorless crystalline solid 1.27 g/cm3[1] 122.41 °C, 396 K, 252 °F (source[3]) 249.2 °C, 522 K, 481 °F ([1]) 2.9 g/L[1] 4.202[2] 1.5397 Structure Monoclinic planar 1.72 D in Dioxane Hazards JT Baker Not listed Irritant

1 2 0 121.5 °C (250.7 °F)[1] 570 °C (1,058 °F)[1]

Related compounds Hydroxybenzoic acids Aminobenzoic acids, Related carboxylic acids Nitrobenzoic acids, Phenylacetic acid Benzaldehyde, Benzyl alcohol, Related compounds Benzoyl chloride, Benzylamine, Benzamide () (what is: / ?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Infobox references

Benzoic acid (pronunciation: /bɛnˈzoʊ.ɪk/), C7H6O2 (or C6H5COOH), is a colorless crystalline solid and a simple aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. Its salts are used as a food preservative and benzoic acid is an important precursor for the synthesis of many other organic substances. The salts and esters of benzoic acid are known as benzoates (pronunciation: /ˈbɛnzoʊ.eɪt/).

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1 History 2 Production o 2.1 Industrial preparations o 2.2 Laboratory synthesis  2.2.1 By hydrolysis  2.2.2 From benzaldehyde  2.2.3 From bromobenzene  2.2.4 From benzyl alcohol  2.2.5 From benzyl chloride  2.2.6 Historical preparation 3 Uses o 3.1 Precursor to plasticizers o 3.2 Precursor to sodium benzoate and related preservatives o 3.3 Medicinal o 3.4 Benzoyl chloride o 3.5 Niche and laboratory uses 4 Biology and health effects 5 Reactions o 5.1 Aromatic ring o 5.2 Carboxyl group 6 References 7 External links

History Benzoic acid was discovered in the sixteenth century. The dry distillation of gum benzoin was first described by Nostradamus (1556), and then by Alexius Pedemontanus (1560) and Blaise de Vigenère (1596).[4] Pioneer work in 1830 through a variety of experiences based on amygdalin, obtained from bitter almonds (the fruit of Prunus dulcis) oil by Pierre Robiquet and Antoine BoutronCharlard, two French chemists, had produced benzaldehyde [5] but they failed in working out a proper interpretation of the structure of amygdalin that would for it, and thus missed the identification of the benzoyl radical C7H5O. This last step was achieved some few months later (1832) by Justus von Liebig and Friedrich Wöhler, who determined the composition of benzoic acid.[6] These latter 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.[citation needed]

U.S. production capacity is estimated to be 126,000 tonnes per year (139,000 tons), 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. 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.[8] The solubility of benzoic acid in over 40 solvents with references to original sources can be found as part of the Open Notebook Science Challenge[9] 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. 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:[10] 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. From benzyl chloride Benzoic acid can be prepared by oxidation of benzyl chloride in the presence of alkaline KMnO4: C6H5CH2Cl + 2 KOH + 2 [O] → C6H5COOK + KCl + H2O Historical preparation 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.

Uses Benzoic acid is mainly consumed in the production of phenol by oxidative decarboxylation at 300−400 °C:[11] C6H5CO2H + 1/2 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.

Precursor to plasticizers Benzoate plasticizers, such as the glycol-, diethylenegylcol-, 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.

Precursor to sodium benzoate and related preservatives

Benzoic acid and its salts are used as a food preservatives, represented by the E-numbers E210, E211, E212, and E213. Benzoic acid inhibits the growth of mold, yeast[12] 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.[13] 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 controlled by international food law.[14][15] 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.[16] 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.[17][18] As the principal component of benzoin resin, 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 antiseptics and inhalant decongestants. Benzoic acid was used as an expectorant, analgesic, and antiseptic in the early 20th century.[19]

Benzoyl chloride Benzoic acid is a precursor to benzoyl chloride, C6H5C(O)Cl by treatment with thionyl chloride, phosgene or one of the chlorides of phosphorus. is an important starting material for several benzoic acid derivates like benzyl benzoate, which is used in artificial flavours and insect repellents.

Niche and laboratory uses In teaching laboratories, benzoic acid is a common standard for calibrating a bomb calorimeter.[20] http://en.wikipedia.org/wiki/Benzoic_acid