3- -benzoic acid

Benzoic acid [65-85-0] C H COOH, the simplest member of the aromatic carboxyHc acid family, was first described in 1618 by a French physician, but it was not until 1832 that its stmcture was deterrnined by Wn b1er and Liebig. In the nineteenth century benzoic acid was used extensively as a medicinal substance and was prepared from gum benzoin. Benzoic acid was first produced synthetically by the hydrolysis of benzotrichloride. Various other processes such as the nitric acid oxidation of toluene were used until the 1930s when the decarboxylation of phthaUc acid became the dominant commercial process. During World War II in Germany the batchwise Hquid-phase air oxidation of toluene became an important process. 

In the United States all other processes have been completely phased out and virtually all benzoic acid is manufactured by the continuous hquid-phase air oxidation of toluene. In the late 1950s and the early 1960s both Dow Chemical and Snia Viscosa constmcted faciUties for Hquid-phase toluene oxidation because of large requirements for benzoic acid in the production of phenol and caprolactam. Benzoic acid, its salts, and esters are very useful and find appHcation in medicinals, food and industrial preservatives, cosmetics, resins, plasticizers, dyestuffs, and fibers. 

Benzoic acid in the free state, or in the form of simple derivatives such as salts, esters, and amides, is widely distributed in nature. Gum benzoin (from styrax ben in) may contain as much as 20% benzoic acid in the free state or in combinations easily broken up by heating. Acaroid resin (from anthorrhoca haslilis) contains from 4.5 to 7%. Smaller amounts of the free acid are found in natural products including the scent glands of the beaver, the bark of the black cherry tree, cranberries, pmnes, ripe cloves, and oil of anise seed. Pern and Tolu balsams contain benzyl benzoate the latter contains free benzoic acid as well. The urine of herbivorous animals contains a small proportion of the glycine derivative of benzoic acid, hippuric acid [495-69-2] (CgH CONHCH2COOH). So-called natural benzoic acid is not known to be available as an item of commerce. 

Selected physical properties of benzoic acid are given in Table 1, solubiHties in water in Table 2, solubiHties in various organic solvents in Table 3, and vapor pressures in Table 4. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Benzoic Acid. The industrial-scale oxidation of toluene to benzoic acid is carried out with cobalt catalysts.973,978,982 983 The process, a free-radical autoxidation, is significantly promoted by bromide ions.984 Under these conditions bromine atoms rather than alkylperoxy radicals serve as a regenerable source of chain-initiating free radicals. Substantial rate increase can be achieved by the addition of manga-nese(II) ions.984 

Liquid-phase oxidation of toluene to benzoic acid (Dow process,980,985,986 Mid-Century process987) may be carried out in acetic acid or without solvent. Cobalt(II) naphthenate or cobalt(II) 2-ethylhexanoate promoted by bromine is used as the catalyst at 140-190°C, at about 8-10 atm pressure. The highly exothermic oxidation is 

Benzoic acid (C6H5COOH, phenyl formic acid, melting point 121.7°C, boiling point 249.2°C, density 1.266) is a white crystalline solid that sublimes readily at 100°C and is volatile in steam. Benzoic acid is insoluble in cold water but is readily soluble in hot water or in alcohol or ether. 

Although benzoic acid occurs naturally in some substances, such as gum benzoin, dragon s blood resin, balsams, cranberries, and the urine of the ox and horse, the product is made on a large scale by synthesis from other materials. Benzoic acid can be manufactured by the liquid-phase oxidation of toluene by air in a continuous oxidation reactor operated at moderate pressure and temperature  

Benzoic acid also can be obtained as a by-product of the manufacture of benzaldehyde from benzal chloride or benzyl chloride. 

Benzoic acid melts at 121.4° and boils at 249°. One hundred parts of water at 17.5° dissolve 0.268 parts, and at 75° dissolve 2.19 parts of the acid. It is readily soluble in alcohol and in ether. The yield should be about 14 grams. 

—In oxidizing aromatic compounds with nitric acid, the latter is usually diluted with water in order to prevent nitration. An acid of the specific gravity 1.15 is ordinarily used. 

Identification of Benzoic Acid Conversion into Benz-anilide.—To definitely identify as benzoic acid an unknown substance which has the melting-point and physical properties of 

Benzoic acid (ben-ZO-ik AS-id) is the simplest of the aromatic carboxylic acids, a family of organic compounds containing the carboxyl (-COOH) group. It occurs in the form of white crystalline needles or thin plates. Many naturally occurring plants contain benzoic acid, including most types of berries and the natural product called gum benzoin, a plant common to the islands of lava, Sumatra, and Borneo. Gum benzoin may contain up to 20 percent benzoic acid. Benzoic acid is also excreted by most animals (except fowl) in the form of a related compound called hippuric acid (C6H5CONHCH2COOH). 

Some benzoic acid is prepared from gum benzoin and other natural compounds containing high concentrations of the compound. Three methods are available for making benzoic acid commercially. In one method, toluene (C6H5CH3) is 

More than half of all the benzoic acid produced in the United States is used in the manufacture of various polymeric products, primarily the family of plastics known as the polyvinyl acetates (PVAs). The PVAs, in turn, are used as adhesives, caulks, sealants, and coatings for paper, film, and plastic foil. About a quarter of all benzoic acid is converted to its sodium and potassium salts, sodium benzoate (C6HsC00Na) and potassium benzoate (C6H5C00K), for use as food preservatives. Sodium benzoate and potassium benzoate are now the most widely used food preservatives in the world. They are added to a host of products, such as soft drinks and fruit juices, jams and jellies, baked goods, and salad dressings. They are also added to a number of non-food products such as mouthwashes, toothpastes, cosmetic creams, and deodorants. 

As an additive to antifreezes, where is acts to prevent corrosion of engine parts  

Benzoic acid and its sodium and potassium salts pose moderate health hazards to people who work directly with them. They may cause skin, nose, and eye problems if inhaled or deposited on the body. In the form of finely divided dust, they may also pose a fire or explosive risk. Most people do not encounter any of these compounds in a form in which they pose a health risk. All three compounds are considered safe by the U.S. Food and Drug Administration as food additives provided their concentration in foods does not exceed o.i percent. Other nations have set a safe level for the three compounds as food additives as high as 

Benzoic acid - calcium salt [II, 8.1.9c.] CA Index Name  

Acidum benzoicum Benzenecarboxylic acid Benzene formic acid Carboxybenzene Phenylformic acid Dracylic acid Phenyl carboxylic acid Purox B E 210. 

German Benzoesaure, French Acide benzoique, Spanish Addo benzoico. 

Sodium benzoate Antimol Benzoate sodium Benzoate of soda Sobenate Benzotron Purox S E 211. 

Health aspects, acute toxicity. Benzoic acid is absorbed in the human body from the intestine and metabolised through enzymes to hippuric acid (benzoyl glycocoll), which is excreted in the urine. Additionally relatively small quantities of benzoic acid are linked to glucuronic acid and excreted in the urine by this route. Pollution arising from cooking fumes of food preserved with benzoic acid is under discussion (Benfenati, et al., 1998). 

Benzoic acid activity is directed both to cell walls and to inhibition of citrate cycle enzymes (a-ketoglutaric acid dehydrogenase, succinic acid dehydrogenase) and of enz)mies involved in oxidative phosphorylation. 

The acid is used in its alkali salt form as an additive, since solubility of the free acid is unsatisfactorily low. However, the undissociated acid 

Benzoic acid is a retarder commonly used by the rubber industry for many years. Because it is a weak organic acid, it increases the scorch safety time of a nonhalo-genated rubber compound. However, it also slows down the cure rate and may lower the ultimate hardness, modulus, and other cured properties of the compound itself. 

Benzoic acid is used as a preservative by the food and drug industries and in certain perfumes. It is also used as an antifungal agent. Only a relatively small quantity is used as a rubber retarder. 

Other organic acid retarders can probably substitute for benzoic acid with only small compound adjustments needed. 

Phthalic anhydride is another common chemical that is sometimes used as a rubber retarder. Because it is an organic acid anhydride, it naturaiiy increases the scorch safety time of a nonhaiogenated rubber-based compound. However, it aiso siows down the cure rate and may hurt the uitimate cured hardness, moduius, and state of cure of the compound itseif. 

Orf/jo-xylene must be separated from the xylene streams, since only the ortho isomer (and not the meta or para) can he converted to phthalic anhydride. 

BP Benzoic acid JP Benzoic acid PhEur Acidum benzoicum USP Benzoic acid 

Benzenecarboxylic acid benzeneformic acid carboxybenzene dracylic acid E210 phenylcarboxylic acid phenylformic acid. 

Benzoic acid is widely used in cosmetics, foods, and pharmaceuticals see Table I), as an antimicrobial preservative. Greatest activity is seen at pH values between 2.5. 5 see Section 10. 

Benzoic acid also has a long history of use as an antifungal agent in topical therapeutic preparations such as Whitfield s ointment (benzoic acid 6% and salicylic acid 3%). 

Benzoic acid occurs as feathery, light, white or colorless crystals or powder. It is essentially tasteless and odorless or with a slight characteristic odor suggestive of benzoin. 

De La Riva Reyero [46] applied HPLC to the determination of benzoic acid in milk. 

Tsuji [47] determined mono, di and triisopropyl citrates in amounts down to 1 pg/g in butter and milk by GC. 

This is a solid that melts at 121°C and is soluble in hot water, alcohol and ethers. It undergoes the same reactions as aliphatic carboxylic acids. 

It forms benzoyl chloride upon reaction with PC13, PC15 or SOCl2 

It forms esters when reacted with alcohols, these products have a pleasant odor. 

Primary and secondary alkyl groups (but not tertiary) directly attached to a benzene ring may be oxidized by KMn04. 

If the carbon attached to the benzene ring is tertiary, no reaction occurs. 

Whereas the nitro derivatives of benzene are produced by electrophilic aromatic substitution, further important derivatives of toluene are predominantly obtained through reactions of the methyl group they include the production of oxidation products such as benzoic acid and the side-chain chlorinated toluene compounds. 

In common with many other aromatic compounds, benzoic acid was first discovered in a renewable raw material, namely gum benzoin, by Blaise de Vigenere as early as in the 16th century. Carl Wilhelm Scheele further studied this raw material in 1755, and it remained the main source for medicinal benzoic acid until the mid-nineteenth century. The first technical synthesis of benzoic acid was based on naphthalene, via the intermediate phthalic anhydride this synthesis was introduced in 1863. In 1877, August Wilhelm von Hofmann reported the synthesis of benzoic acid from hippuric acid, which is present in the urine of herbivores. 

The production of benzoic acid from naphthalene, practised up to the end of World War II, is possible in one stage, without the isolation of the intermediate phthalic acid. Oxidation of naphthalene is carried out at 340 °C with zinc oxide. This decarboxylates the phthalic acid in the gas-phase however, conversion in this reaction is not complete, and the benzoic add must be separated from the phthalic acid. Separation is possible by dissolving the phthalic acid in water. 

Decarboxylation of phthalic acid in the liquid-phase also leads to the production of benzoic acid. In this process, developed by Monsanto, liquid phthalic anhydride is converted over nickel oxide or copper oxide with the introduction of steam at 220 °C. 

Nowadays, benzoic acid is obtained on a commercial scale virtually exclusively by the oxidation of toluene with air. 

Derivative benzoates and parabenzoates have been used primarily in fruit juices, chocolate syrup, pie fillings, pickled vegetables, relishes, horseradish, and cheese (Barbosa-Canovas et al., 2003). Other foodstuffs where sodium benzoate is used include soft drinks, baked goods, and lollipops (Poulter, 2007). Benzaldehyde and benzoic alcohol are better known to be yeast inhibitors. Benzoic acid has been found to release fewer protons than sulphite, nitrite, or acetic acid and it may be speculated that benzoic acid is not a classic weak-acid preservative. However, due to a lower pKa value, benzoic acid releases three to four times more protons than sorbic acid. This is a sizable concentration of protons although not as much as other weak-acid preservatives (Stratford and Anslow, 1998). Inhibition of growth is strongly pH-dependent and most effective under acidic conditions. Under these conditions the protonated form of the acid is predominantly found (Visti, Viljakainen, and Laakso, 2003). Another unexpected discovery was that benzoic acid appears to be a pro-oxidant. This was unexpected as it is a well-known fact 2-hydroxybenzoic acid (or salicylic acid) acts as a scavenger of free radicals in vivo (Piper, 1999). 

Properties.—Crj stallises in needles m. p. 121° on heating it melts and sublimes soluble in hot water, alcohol and ether. It distils in steam. 

Reactions.—i. Make a neutral solution of ammonium benzoate by adding excess of ammonia to benzoic acid and boiling until neutial. To different poitionsadd solutions of calcium chloi ide, ferric chloride, silver nitrate and lead acetate and note the results. 

Synonyms Benzofuran benzo(/ )furan coum-arone cumarone 1-oxindene 

As an intermediate in the polymerization of coumarone-indene resins found in various corrosion-resistant coatings such as paints and varnishes in water-resistant coatings for paper products and fabrics in adhesives for use in food containers 

Toxicology. Benzofuran is carcinogenic in experimental animals and causes kidney damage. 

Exposure to benzofuran increased the severity of nephropathy in male rats, increased the incidence of nephropathy in female rats, and induced hepatocellular metaplasia in the pancreas of female rats. Nonneoplastic lesions observed in mice included syncytial alteration 

Although no studies provide data concerning human susceptibility, it is reasonable to assume that humans with kidney or liver disease would be more susceptible to the toxic effects of 2,3-benzofuran.  

The use of sodium or potassium benzoate is approved by BATF for stabilization of wine coolers but not table wines. Although permitted for use at levels up to 1000 mg/L, sensory considerations require use at much lower levels. In wine coolers, benzoate is frequently used in combination with sorbate and SO2. The combination provides the needed level of antimicrobial activity at concentration levels that are generally not sensorially objectionable (Zoecklein et al., 1995). Carbonation may also enhance antimicrobial effects. In soft drinks, Schmidt (1987) reported linear decreases in the concentration of sodium benzoate required with increases in carbonation. 

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It is readily oxidized by air to benzoic acid. With aqueous KOH gives benzyl alcohol and benzoic acid. Gives addition products with hydrogen cyanide and sodium hydrogen sulphite. 

It was first described in 1608 when it was sublimed out of gum benzoin. It also occurs in many other natural resins. Benzoic acid is manufactured by the air oxidation of toluene in the liquid phase at 150°C and 4-6 atm. in the presence of a cobalt catalyst by the partial decarboxylation of phthalic anhydride in either the liquid or vapour phase in the presence of water by the hydrolysis of benzotrichloride (from the chlorination of toluene) in the presence of zinc chloride at 100°C. 

Much of the benzoic acid produced is converted to sodium benzoate, which is used as a food preservative (as is the acid) and a corrosion inhibi tor. Other important uses of the acid are in the manufacture of alkyd resins, plasticizers, caprolactam, dyestuffs and pharmaceuticals. 

Prepared by the dehydration of benzamide. Hydrolysed by dilute acids and alkalis to benzoic acid. Good solvent. benzopheDone,C]3HioO,PhC(0)Ph. Colourless rhombic prisms, m.p. 49 C, b.p. 306°C. Characteristic smell. It is prepared by the action of benzoyl chloride upon benzene in the presence of aluminium chloride (Friedel-Crafts reaction) or by the oxidation of di-phenylmethane. It is much used in perfumery. Forms a kelyl with sodium. 

It is prepared by fully chlorinating toluene. When heated with water at 100°C, or with lime, benzoic acid is obtained, benzoyl The group PhC(O)-. 

Cannizzaro reaction Two molecules of many aldehydes, under the influence of dilute alkalis, will interact, so that one is reduced to the corresponding alcohol, while the other is oxidized to the acid. Benzaldehyde gives benzyl alcohol and benzoic acid. Compare the aldol condensation. 

CgHgO, PhCH = CHCOiH. Colourless crystals. Decarboxylales on prolonged heating. Oxidized by nitric acid to benzoic acid. Ordinary cinnamic acid is the trans-isomer, m.p. 135-136 C on irradiation with u.v. light it can be isomerized to the less stable cis-isomer, m.p. 42" C. 

Hammen equation A correlation between the structure and reactivity in the side chain derivatives of aromatic compounds. Its derivation follows from many comparisons between rate constants for various reactions and the equilibrium constants for other reactions, or other functions of molecules which can be measured (e g. the i.r. carbonyl group stretching frequency). For example the dissociation constants of a series of para substituted (O2N —, MeO —, Cl —, etc.) benzoic acids correlate with the rate constant k for the alkaline hydrolysis of para substituted benzyl chlorides. If log Kq is plotted against log k, the data fall on a straight line. Similar results are obtained for meta substituted derivatives but not for orthosubstituted derivatives. 

Obtained synthetically by one of the following processes fusion of sodium ben-zenesulphonate with NaOH to give sodium phenate hydrolysis of chlorobenzene by dilute NaOH at 400 C and 300atm. to give sodium phenate (Dow process) catalytic vapour-phase reaction of steam and chlorobenzene at 500°C (Raschig process) direct oxidation of cumene (isopropylbenzene) to the hydroperoxide, followed by acid cleavage lo propanone and phenol catalytic liquid-phase oxidation of toluene to benzoic acid and then phenol. Where the phenate is formed, phenol is liberated by acidification. 

Aluminum complex greases, obtained by the reaction of aluminum isopropylate with a mixture of benzoic acid and fatty acids. These greases have a remarkable resistance to water, very good adhesion to metallic surfaces, good mechanical stability properties and resistance to temperature. They are less common than the first two types. 

With most non-isothemial calorimeters, it is necessary to relate the temperature rise to the quantity of energy released in the process by determining the calorimeter constant, which is the amount of energy required to increase the temperature of the calorimeter by one degree. This value can be detemiined by electrical calibration using a resistance heater or by measurements on well-defined reference materials [1], For example, in bomb calorimetry, the calorimeter constant is often detemiined from the temperature rise that occurs when a known mass of a highly pure standard sample of, for example, benzoic acid is burnt in oxygen. 

The logarithm of the equilibrium constant, K,. for the chemical equation shown in Figure 3-8a for a substituted benzoic acid can be related to the logarithm of the... 

Figure 3-8 a) The dissociation of substituted benzoic acids (X = substituent), and b) the hydrolysis of benzoic acid methyl esters. 

A limitation of the ap and tt descriptors is the specificity of the atom typing, e.g., benzoic acid and phenyltetrazole would not be perceived as very similar, even though carboxylates and tetrazoles are both anions at physiological pH. 

Fig. 12.20 4-Acetamido benzoic acid. Triangle smoothing predicts that the lower bound distance between the amide nitrogen and the carbonyl oxygen is equal to the sum of the van der Waals radii. The actual distance is about 6.4A.

Benzoic acid Succinic. anhydride Hexacetyl mannitol ... 

Place 20 g. of benzoic acid and 20 ml. (16 g.) of ethanol in A, connect up the apparatus, and then heat the flask on a sand-bath so that the solution in the flask boils gently. At the same time, pass a brisk current of hydrogen chloride into the reaction... 

When the phenol contains a carboxylic acid group, e.g., m- or p-hydroxy-benzoic acid, the acetylated derivative will of course remain in solution as the sodium salt, but is precipitated when the solution is subsequently acidified. Salicylic acid, however, cannot be acetylated under these conditions. 

It should be noted that aliphatic compounds (except the paraffins) are usually oxidised by concentrated nitric acid, whereas aromatic compounds (including the hydrocarbons) are usually nitrated by the concentrated acid (in the presence of sulphuric acid) and oxidised by the dilute acid. As an example of the latter, benzaldehyde, CjHsCHO, when treated with concentrated nitric acid gives ffi-nitrobenzaldehyde, N02CgH4CH0, but with dilute nitric acid gives benzoic acid, CgHgCOOH. 

Place I g. of benzamide and 15 ml. of 10% aqueous sodium hydroxide solution in a 100 ml. conical flask fitted with a reflux water-condenser, and boil the mixture gently for 30 minutes, during which period ammonia is freely evolved. Now cool the solution in ice-water, and add concentrated hydrochloric acid until the mixture is strongly acid. Benzoic acid immediately separates. Allow the mixture to stand in the ice-water for a few minutes, and then filter off the benzoic add at the pump, wash with cold water, and drain. Recrystallise from hot water. The benzoic acid is obtained as colourless crystals, m.p. 121°, almost insoluble in cold water yield, o 8 g. (almost theoretical). Confirm the identity of the benzoic acid by the tests given on p. 347. 

Benzamide from Benzonitrile. (A) Although benzonitrile when boiled with 70% sulphuric acid undergoes ready hydrolysis to benzoic acid (see above), treatment with hot 90% sulphuric acid gives the intermediate benzamide. This difference arises partly from the difference in temperature employed, but also... 

Hydrolysis of />-Tolunitrile. As in the case of benzonitrile, alkaline h> drolysis is preferable to hydrolysis by 70% sulphuric acid. Boil a mixture of 5 g. of p-tolunitrile, 75 ml. of 10% aqueous sodium hydroxide solution and 15 ml. of ethanol under a reflux water-condenser. The ethanol is added partly to increase the speed of the hydrolysis, but in particular to prevent the nitrile (which volatilises in the steam) from actually crystallising in the condenser. The solution becomes clear after about i hour s heating, but the boiling should be continued for a total period of 1-5 hours to ensure complete hydrolysis. Then precipitate and isolate the p-toluic acid, CH3CgH4COOH, in precisely the same way as the benzoic acid in the above hydrolysis of benzonitrile. Yield 5 5 g. (almost theoretical). The p-toluic acid has m.p. 178°, and may be recrystallised from a mixture of equal volumes of water and rectified spirit. 

Prepare a mixture of 30 ml, of aniline, 8 g. of o-chloro-benzoic acid, 8 g. of anhydrous potassium carbonate and 0 4 g. of copper oxide in a 500 ml. round-bottomed flask fitted with an air-condenser, and then boil the mixture under reflux for 1 5 hours the mixture tends to foam during the earlier part of the heating owing to the evolution of carbon dioxide, and hence the large flask is used. When the heating has been completed, fit the flask with a steam-distillation head, and stcam-distil the crude product until all the excess of aniline has been removed. The residual solution now contains the potassium. V-phenylanthrani-late add ca. 2 g. of animal charcoal to this solution, boil for about 5 minutes, and filter hot. Add dilute hydrochloric acid (1 1 by volume) to the filtrate until no further precipitation occurs, and then cool in ice-water with stirring. Filter otT the. V-phcnylanthranilic acid at the pump, wash with water, drain and dry. Yield, 9-9 5 g. I he acid may be recrystallised from aqueous ethanol, or methylated spirit, with addition of charcoal if necessary, and is obtained as colourless crystals, m.p. 185-186°. 

Benzyl Alcohol, CeH5CH20H, and Benzoic Acid, CaHsCOOH. (Cannizzaro s Reaction). 

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