Benzoic acid, preparation

Phenol can also be prepared by the decomposition of benzoic acid prepared by the oxidation of toluene.927,978 The process is an oxidative decarboxylation catalyzed by copper(II). An interesting feature of this reaction is that the phenolic hydroxyl group enters into the position ortho to the carboxyl group as was proved by 14C labeling.979 In the Dow process980 molten benzoic acid is transformed with steam and air in the presence of Cu(II) and Mg(II) salts at 230-240°C. A copper oxide catalyst is used in a vapor-phase oxidation developed by Lummus.981... 

The benzoic acid prepared by an air oxidation of toluene contains small amounts of various compounds that decrease the catalytic activity of platinum metal catalysts. The benzoic acid purified by sublimation is hydrogenated much more rapidly than an unpurified one. On a large scale, however, treatment of commercial benzoic acid with Pd-C at 100-200°C under high hydrogen pressure in a solvent for hydrogenation or, better, treatment with 0.2-10% (for benzoic acid) of concentrated sulfuric acid at... 

Benzoic acid is often combined with sorbic acid in order to reduce its peculiar flavor. It has to be stated, however, that this is at least partly caused by impurities in the benzoic acid preparation used. 

Benzoic acid prepared catalytically from phthalic anhydride may contain certain undesirable compounds, tars, and coloring materials and must of necessity be purified in some cases to obtain a marketable product. Naphthoquinone impurities are reduced to naphthohydroquinones by treatment of the product with sulfur dioxide or sodium bisulfite at 40° to 50° C. for 3 to 4 hours. Any phthalic anhydride remaining is converted to phthalic acid at the same time. Leaching with water is used to remove the reduced impurities.72 Unconverted phthalic acid may also be separated from benzoic by treatment of the mass with sodium carbonate so as to convert the polycarboxylic acid into a primary salt while leaving the mono-carboxylic acid unreacted. Solvent leaching is then used to separate the salt from the acid.78 Colored impurities in benzoates from synthetic benzoic acid may be removed by oxidation with potassium permanganate.71... 

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)-. 

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°. 

Benzanihde is more conveniently prepared, particularly on a larger scale, by heating together aniline and benzoic acid ... 

The preparation of a number of miscellaneous acids is described. m-Nitrobenzoic acid. Although m-nitrobenzoic acid is the main product of the direct nitration of benzoic acid with potassium nitrate and concentrated sulphuric acid, the complete separation of the small quantity of the attendant para isomer is a laborious process. It is preferable to nitrate methyl benzoate and hydrolyse the resulting methyl w-nitrobenzoate, which is easily obtained in a pure condition ... 

Dinitrobenzoic acid. This acid may be prepared by the nitration of benzoic acid with a mixture of concentrated sulphuric acid and fuming nitric acid under special conditions (see also Section VII,22) ... 

Anthranilic acid. This substance, the ortho amino derivative of benzoic acid, may be conveniently prepared by the action of sodium hypobromite (or sodium hypochlorite) solution upon phthalimide in alkaline solution at 80°. The ring in phthalimide is opened by hydrolysis to phthalamidic acid and the latter undergoes the Hofmann reaction (compare Section 111,116) ... 

Method 2. This preparation should be carried out in the fume cupboard since nitrous fumes are evolved. Place 62 g. of benzoic acid and 300 ml. of concentrated sulphuric acid in a 2-litre roimd-bottomed flask, warm on a water bath with shaldng until the benzoic acid dissolves, and cool to 20°. Add 100 ml. of fuming nitric acid (sp. gr. 1-54) in portions... 

Prepare p-chlorobenzoyl chloride by refluxing and stirring 78 g. of p-chloro-benzoic acid (Section IV,157) and 100 g. of redistilled thionyl chloride until solution is complete. Distil off the excess of thionyl chloride at atmospheric pressure and then the acid chloride under reduced pressure 70 g. of product, b.p. 119-120°/ 22 mm., m.p. 14-15°. are obtained. 

Owing to the greater stability and the easier preparation, monoperphthalic acid is generally preferred to benzoic acid. 

The isocoumarin 151 is prepared by the intramolecular reaction of 2-(2-propenyDbenzoic acid (149) with one equivalent of PdCbjMeCN) . However, the (Z)-phthalide 150 is obtained from the same acid with a catalytic amount of PdjOAc) under 1 atm of Oi in DMSO, alone is remarkably efficient in reoxidizing Pd(0) in DMSO. The isocoumarin 151 is obtained by the reaction of 2-(l-propenyl)benzoic acid (152) under the same conditions[4], 2-Vinylbenzoic acid (153) is also converted into the isocoumarin 154, but not to the five-membered lactone) 167,170],... 

Benzoic acid and naphthoic acid are formed by the oxidative carbonylation by use of Pd(OAc)2 in AcOH. t-Bu02H and allyl chloride are used as reoxidants. Addition of phenanthroline gives a favorable effect[360], Furan and thiophene are also carbonylated selectively at the 2-position[361,362]. fndole-3-carboxylic acid is prepared by the carboxylation of 1-acetylindole using Pd(OAc)2 and peroxodisulfate (Na2S208)[362aj. Benzoic acid derivatives are obtained by the reaction of benzene derivatives with sodium palladium mal-onate in refluxing AcOH[363]. 

In 1825 Michael Faraday isolated a new hydrocarbon from illuminating gas which he called bicarburet of hydrogen Nine years later Eilhardt Mitscherlich of the University of Berlin prepared the same substance by heating benzoic acid with lime and found it to be a hydrocarbon having the empirical formula C H ... 

A clear cut answer was provided by Irving Roberts and Harold C Urey of Colum bia University in 1938 They prepared methanol that had been enriched in the mass 18 isotope of oxygen When this sample of methanol was esterified with benzoic acid the... 

Because cyano groups may be hydrolyzed to carboxylic acids (Section 20 19) the Sand meyer preparation of aryl nitriles is a key step m the conversion of arylammes to sub stituted benzoic acids In the example just cited the o methylbenzomtnle that was formed was subsequently subiected to acid catalyzed hydrolysis and gave o methylbenzoic acid in 80-89% yield... 

The Kolbe-Schmitt reaction has been applied to the preparation of other o hydroxy benzoic acids Alkyl derivatives of phenol behave very much like phenol itself... 

Dihydroxybenzophenones are used for the syntheses of dyes, polymers, and medicines. They are prepared by the condensation of resorcinol with benzoic acids. Catalysts used for this transformation are sulfonic resins (99), boron trifluoride (100), or zinc chloride in the presence of POCl (101). 

Propiophenone. Propiophenone [93-55-0] (ethyl phenyl ketone) is a colorless Hquid with a flowery odor. It can be prepared by the Friedel-Crafts reaction of benzene and propionyl chloride in the presence of aluminum chloride (346), or by the catalytic reaction of benzoic acid and propionic acid in the presence of water (347). Propiophenone is commercially available (348), and is sold in Japan at 2700 Y/kg (349). It is used in the production of ephedrine, as a fragrance enhancer, and as a polymerization sensitizer. 

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