Aromatic anhydrides

However, certain additives can decrease the rate of thermal decomposition [28]. These additives include cyclic sulfates, sulfones, sultones, aliphatic and aromatic anhydrides, and polymers with pendant carboxylic acid functional groups. Most of these materials are latent acids, which decompose on heating in the presence of moisture to form a strong acid, as shown for cyclic sulfate, 9, in Eq. 5. 

By use of TV-(trifluoroacetyl)- or TV-(trichloroacetyl)-imidazoleare obtained symmetric aliphatic and aromatic anhydrides even from carboxylic acids that do not form insoluble salts in benzene, ether, or THF (Table 13—1). In this case the acid is treated with the imidazolide in a 2 1 molar ratio, and an insoluble imidazolium trifluoro- or tri-chloroacetate is formed. 

Another Pd-catalyzed reaction of aryl- and alkylzinc halides used carboxylic anhydrides as starting organic compounds (Scheme 127).328 One of the advantages of this method is that anhydrides can be synthesized in situ from the corresponding sodium salts of carboxylic acids and ethyl chloroformate. The scope of the method includes aliphatic and aromatic anhydrides, phenyl-, ethyl-, isopropyl-, and n-butylzinc iodides. 

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). 

Quinophthalones. The quinophthalone pigments are prepared by condensation of quinaldincs with a variety of aromatic anhydrides. One pigment in this series, Pigment Yellow 138, is a reasonably weatherfast greenish yellow pigment of good heat stability. The main field of application is paints and plastics. 

The simpler examples are readily hydrolysed in aqueous solution, and therefore react with sodium hydrogen carbonate and also give the ester test they may be confirmed by applying the hydroxamic ester test (Section 9.5.3, p. 1222). Carbonyl adsorption is apparent in the infrared spectrum at about 1820 cm-1 and at about 1760cm-1. It should be noted that aromatic anhydrides and higher aliphatic anhydrides are not readily hydrolysed with water and are therefore effectively neutral (Section 9.5.3, p. 1218). The final characterisation of the acid anhydride is achieved by conversion into a crystalline carboxylic acid derivative as for add halides. 

Dicarboxylic acids are readily converted into cyclic anhydrides when heated alone or in acetic anhydride. Heat 0.5 g of the acid in 2-3 ml of refluxing acetic anhydride for 30 minutes. Remove most of the excess reagent by distillation and crystallise the residual cyclic anhydride from chloroform or toluene. The melting points of aliphatic and aromatic anhydrides are to be found in Tables 10.23 and 10.24 respectively. For conversion of the anhydrides into anilic acids see Section 9.6.16, below. 

C. Arynes from Aromatic Anhydrides Other Than Phthalic. . . 15... 

II. Arynes from Aromatic Anhydrides A. Reactions of Benzyne with Benzene... 

C. Arynesfrom Aromatic Anhydrides Other than Phthalic... 

Other aromatic anhydrides also exhibit parallel behavior upon electrou impact and pyrolysis. The mass spectra of naphthalene-2,3-dicarboxylic anhydride and 1,8-naphthalic anhydride are qualitatively similar (Fields and Meyerson, 1967d) ... 

Yields were calculated on the basis of aromatic anhydride. For example, 0-01 mole of phthalic anhydride with excess pyridine theoretically should give a total of 0-01 mole of the products of insertion and... 

The reactions of a series of arynes from aromatic anhydrides with thiophene and benzothiophene at 690° revealed some processes not as clearly evident with other reagents. 

Yields were calculated as in Section E on the basis of aromatic anhydride. 

Quinolinic anhydride decomposes at a lower temperature than do the aromatic anhydrides (Fields and Meyerson, 1967e). For this reason, it was allowed to react with thiophene at 600° and 40 sec contact time. The products, quinoline, pyridothiophene, and pyridylthiophene, are those expected from the 1,4- and 1,2-additions and insertion of pyridyne with thiophene ... 

As tetraphenylphthalic anhydride behaved quite differently from the other aromatic anhydrides, its mass spectrum and reactions at high temperatures (Fields and Meyerson, 1967f) are described separately. A partial mass spectrum is shown in Table 12. 

The spectrum of benzoic anhydride in Figure 2.27 is that of a typical aromatic anhydride. 

Synthesis of Polymers. Polyamic acid solutions were prepared by condensation of the aromatic anhydride and amine in N,N-dimethylacetamide (DMAc). Polyimide modified electrodes were made by casting or spin coating the precursor polyamic acid solution onto stainless steel or platinum substrates. Imidization was achieved by either heating the films to 400°C for 60 min or through a chemical dehydration process involving immersion in a 1 1 mixture of acetic anhydride and pyridine (6). BTDA-DAPI films were made by casting from a DMAc solution and heating to 100 C. 

Novel polymers have been prepared by the Diels-Alder reaction of two bis(isobenzofuran)s and a series of bis(acetylene) imides. Bis(isobenzofuran) 317 was prepared from phenylphthalide precursors. Two varieties of bis(acetylene)s 318 and 319 were prepared by the reaction of various aromatic anhydrides with amine 320 (Equation 7) or by the reactions of various diamines 321 with 4-phenylethynylphthalic anhydride 322 (Equation 8). One example of the polymers formed is 323 (Equation 9) <2000MI299>. 

Maleic anhydride and several related derivatives have been added to a large number of dienes. Reaction of butadiene with maleic anhydride occurs at 50° in benzene solution to give 1,2,3,6-tetrahydrophthalic anhydride (97%). This method furnishes many important partially hydrogenated aromatic anhydrides, most of which are outside the scope of this book. An excellent discussion of the reaction and survey of the literature to 1945 has been made (cf. method 34). 

A Variety of ketones may be made using cadmium alkyls (50-70%). In the preparation of alkyl aryl ketones, reaction of the aliphatic rather than the aromatic anhydride is preferred. Keto acids result when phthalic anhydride or dimethylsuccinic anhydride (60-70%) is used. 

Stirred in an ice bath during dropwise addition of a 15.5% solution of phosgene in toluene (vigorous gas evolution). After standing overnight the mixture was evaporated to dryness in vacuum, and the anhydride (3) isolated by extraction with benzene and crystallization. Several aliphatic and aromatic anhydrides were obtained by this method in excellent yield. 

Carbonyl groups of simple aliphatic aldehydes, ortho mdpara quinones, a,P-unsaturated carbonyls and cyclic aromatic anhydrides are known to condense with trimethyl phosphite, producing phosphite esters [62]. Lebo and Lonsky used trimethyl phosphite to determine the light-induced formation of ort/jo-quinonoid functional groups in refiner mechanical pulp [63]. 

The reaction of trimellitic anhydride (7) with ethanolamine (9) giving the hydroxy acid (10) and with 4,4 -diaminodiphenylmethane (8) giving the diacid (11) has been published in the first poly(ester-imide) patent [l].The second one is nowadays the predominant reaction for making poly(ester-imide)s. Trimellitic anhydride is the basic dianhydride for introducing the imide structure into the polyesters. Nearly every example in patents is based on trimellitic anhydride alone or mixtures with other anhydrides, e.g., tetrahydrophthalic anhydride [59]. The imides made from aromatic anhydrides are thermally more stable than the ones resulting from aliphatic structures (Fig. 4). Both types have been protected by patents, and products made from them are on the market. 

---