Benzoic acid anhydride formation

Matejka et al. 51> studied the reaction of phenyl glycidyl ether (PGE) with acetic or benzoic acid anhydride in the presence of benzyldimethylamine and also with benzoic acid as a co-catalyst. They found that the tert-amine is bound irreversibly through the formation of a quartemary ammonium salt as shown below. 

Because of a possible similarity between them and the group of reactions just dealt with, it is convenient to mention here some reactions which have been used to prepare carboxylic acid anhydrides. Minunni observed the formation of benzoic acid anhydride in high yield when benzoylpyridinium chloride was treated with water, and the reaction is generally useful . From the fatty acid series the reaction of heptoyl chloride with pyridine in benzene, followed by the addition of heptoic acid, provides an example of anhydride formation in high yield . More recently, anhydrides were prepared from acid chlorides and aqueous solutions of the corresponding sodium salts containing catalytic amounts of pyridine . It seems possible that... 

The formation of phenyl benzoate was both unexpected and inexplicable. GC-MS fragmentation patterns of pure benzoic acid anhydride dissolved in dried toluene indicated the presence of phenyl benzoate. It is possible that due to the high split-inlet temperature (250°) in the gas chromatograph, the anhydride decomposes to the ester with the loss of CO. 

Catalysis in Transacylation Reactions. The principal objective of the study was to evaluate 4 as an effective organic soluble lipophilic catalyst for transacylation reactions of carboxylic and phosphoric acid derivatives in aqueous and two-phase aqueous-organic solvent media. Indeed 4 catalyzes the conversion of benzoyl chloride to benzoic anhydride in well-stirred suspensions of CH2CI2 and 1.0 M aqueous NaHCC>3 (Equations 1-3). The results are summarized in Table 1 where yields of isolated acid, anhydride and recovered acid chloride are reported. The reaction is believed to involve formation of the poly(benzoyloxypyridinium) ion intermediate (5) in the organic phase (Equation 1) and 5 then quickly reacts with bicarbonate ion and/or hydroxide ion at the interphase to form benzoate ion (Equation 2 and 3). Apparently most of the benzoate ion is trapped by additional 5 in the organic layer or at the interphase to produce benzoic anhydride (Equation 4), an example of normal phase-... 

When benzoic acid is heated above its melting point in a sealed container, some formation of benzoic anhydride and water takes place [8]. When the acid is heated to 370°C, it is irreversibly decomposed to benzene and carbon dioxide, and a small portion (2-8%) decomposes into phenol and carbon monoxide. Copper and cadmium powder increase the reaction rate by factors of approximately 9-fold and 200-fold, respectively. 

Friedrichsen and co-workers (133) approached substituted benzotropolones from an aromatic substituted carbonyl ylide with a tethered alkyne as the intramolecular dipolarophUe (Scheme 4.67). Starting from an aromatic anhydride, Friedrichsen was able to make the tethered alkyne via addition of either pentyn-ol or hexyn-ol, then transform the recovered benzoic acid to the a-diazocarbonyl cycloaddition precursor. Addition of rhodium acetate resulted in the tandem formation of cyclic carbonyl ylide followed by cycloaddition of the tethered alkyne producing the tricyclic constrained ether 252. Addition of BF3 OEt2 opened the ether bridge, forming the benzotropylium ion, which subsequently rearranged to form the tricyclic benzotropolone (253). 

The gas-phase selective oxidation of o-xylene to phthalic anhydride is performed industrially over vanadia-titania-based catalysts ("7-5). The process operates in the temperature range 620-670 K with 60-70 g/Nm of xylene in air and 0.15 to 0.6 sec. contact times. It allows near 80 % yield in phthalic anhydride. The main by-products are maleic anhydride, that is recovered with yields near 4 %, and carbon oxides. Minor by-products are o-tolualdehyde, o-toluic acid, phthalide, benzoic acid, toluene, benzene, citraconic anhydride. The kinetics and the mechanism of this reaction have been theobjectof a number of studies ( 2-7). Reaction schemes have been proposed for the selective pathways, but much less is known about by-product formation. 

SAMPLE SOLUTION (a) The reaction given is the acid-catalyzed esterification of methanol by benzoic anhydride. The tetrahedral intermediate is formed by addition of a molecule of methanol to one of the carbonyl groups of the anhydride. This reaction is analogous to the acid-catalyzed formation of a hemiacetal by reaction of methanol with an aldehyde or ketone. 

Product distributions. The reaction was conducted at 550°C by changing the contact time, while fixing the other conditions as presented under Experimental. The main products were benzaldehyde and carbon oxides. The formation of benzoic acid, acetic acid, and maleic anhydride was also detected, but their amounts were much smaller. The yields of each product are shown as a function of the toluene conversion in Fig. 1. The selectivities are given by the slopes from the origin (dashed lines). The selectivity to benzaldehyde decreases with an increase in conversion, while that to carbon oxides increases, indicating that the benzaldehyde formed initially is oxidized gradually to carbon oxides. 

The mechanism of 2-phenylbenzoxazole (162) formation from benzoic acid and o-aminophenol in polyphosphoric acid has been studied by NMR and chemical analysis.135 Initially benzoic acid reacts with (162) to form benzoic phosphoric anhydride and benzoic polyphosphoric anhydride. When o-aminophenol dissolves in... 

The aroylation of an aromatic system by reaction with phthalic anhydride under Friedel-Crafts conditions is described in Section 6.11.1, p. 1006. The cyclisation of the derived o-aroylbenzoic acid with polyphosphoric acid is a convenient route to substituted anthraquinones. The reaction is illustrated by the formation of 2-methylanthraquinone from o-(p-toluoyl)benzoic acid (Expt 6.132). 

The end-chain aromatic ketone (1690 cm-1) may react photochemically by a Norrish type 1 reaction, leading to the formation of benzaldehyde (1704 cm-1) and benzoic acid (1698-1732cm-1). No detailed mechanism can be proposed for the formation of benzoic anhydride (1725-1785 cm-1) since several plausible routes exist. 

Esters have been prepared in 63-73% yields from several simple cycloalkyl and aryl alkyl ketones by reaction at room temperature with per-benzoic acid. The larger radical of the ketone appears as the alcohol fragment of the ester. Cyclic ketones are oxidized by potassium persulfate and sulfuric acid to esters from which o>-hydroxy aliphatic esters are obtained upon hydrolysis and reesterification. Peracetic acid in acetic anhydride converts salicylaldehyde to o-hydroxyphenyl formate (88%). ... 

Although this is the classical method of anhydride formation it has been replaced to a large extent by the acylation of free carboxylic acids (method 341). The conditions employed and the solvents used in this reaction vary widely. Excellent directions are given for the preparations of nicotinic anhydride (89%) and acetic propionic anhydride (60%) from the respective potassium and sodium salts of the carboxylic acids. Silver salts of acids have also been used. The reaction has been extended to the preparation of mixed anhydrides of short- and long-chain fatty acidsbut has failed in the preparation of mixed anhydrides of substituted benzoic acids. ... 

The reaction of oarboxylate with various substrates is an example of a system which necessitates a careful search for products. Early examples of these reactions demonstrated that direct nucleophilic attack takes place. For example, using a dilatometric method, formate was found to catalyze strongly the hydrolysis of acetic anhydride whereas propionate and butyrate slow down the reaction (Kilpatrick, 1928). These results are attributable to mixed anhydride formation with the total rate being determined by the reactivity of the mixed anhydride. The reaction of acetate with 2,4-dinitrophenyl benzoate results in the formation of an unstable mixed anhydride, as was shown in an experiment in which 0 labeled acetate was used the benzoic acid product contains 75% of the O label (Bender and Neveu, 1958). The other 25 % of the O label is presumed to be lost to acetate by solvent attack at the benzoyl carbon if direct nucleophilic interaction is the sole path. 

Acetylation, formylatlon, and benzoylation of a variety of primary and secondary alcohols with the respective acids (acetic acid or anhydride, ethyl formate, and benzoic anhydride) can be achieved under the catalysis of BiCls, Bi(OCOCF3)3, or Bi(OTf)3 (Scheme 14.97) [194—196]. The O-acylahon of phenols is also promoted by these Lewis acids. Among the bismuth(III) salts employed, Bi(OTf)3 is the most effechve in terms of reaction condihons and yields of the esters. The Bi(OTf)3-acid anhydride procedure is apphcable to the acylahon of sterically demanding or tertiary alcohols and phenols. Treatment of terhary or benzylic bromides with Bi(OCOR)3 (R=Me, Ph) affords the corresponding esters [197]. In the presence of a catalytic amount of 612(804)3, the esterificahon of cis-(-)-thujopsene with a series of C2-C8 acids proceeds in moderate yield [198]. 

The low value of the raw materials compared to the premium price paid for chloride-free benzaldehyde and benzoic acid makes the commercial utilization of the process attractive despite the difficulties involved. The production of benzoic acid by the direct oxidation of toluene lias not reached the proportions that benzaldehyde has. lthough the production of beuzoic acid directly is feasible with the correct catalysts, small quantities only from this source are being marketed and are obtained as a by-product of the catalytic oxidation of toluene to benzaldehyde. Because of the difficulty in the selection of correct catalysts, the oxidation oi toluene to benzoic acid is complicated by the oxidation going too far with resultant loss of raw material or by the formation of gummy condensation products intermixed with the benzaldehyde, benzoic acid, maleic acid and anthra-quinone. These complications have deterred commercial application of the oxidation process in the face of the newer process for forming benzoic acid by the decarboxylation of phthalic anhydride. 

The further oxidation of benzaldehyde to benzoic acid is complicated also by the numerous condensations and polymerizations that occur. At 350° C. benzaldehyde decomposes to benzyl benzoate with the formation of some benzene and carbon monoxide.128 At the same temperature benzyl benzoate decomposes to benzoic anhydride, toluene, and benzalde-hyde. At temperatures of 700° C. carbon monoxide and benzene are the chief decomposition products of benzaldehyde and some diphenyl and triphenyl also form. In the presence of catalysts aud oxygen further reactions lead to the formation of complicated gums and tars which involve losses, make separation of the product difficult and effectively destroy the activity of the catalyst by coating it over. 

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