Dicarboxylates, aromatic

Polycarbonates. Polyarjiates are aromatic polyesters commonly prepared from aromatic dicarboxylic acids and diphenols. One of the most important polyarylates is polycarbonate, a polyester of carbonic acid. Polycarbonate composite is extensively used in the automotive industry because the resin is a tough, corrosion-resistant material. Polycarbonates (qv) can be prepared from aUphatic or aromatic materials by two routes reaction of a dihydroxy compound with phosgene accompanied by Hberation ofHCl(eq. 5) ... 

PolybenZimidaZoles. The polyben2imida2oles (PBIs) are generally produced by the high temperature, melt polycondensation reaction of aromatic bis-ortho-diamines and aromatic dicarboxylates (acids, esters, or amides) in a reaction such as that shown in equation 11 to form ben2imida2ole [51-17-2] as the repeating unit. 

The present method for preparing aromatic dicarboxylic acids has been used to convert phthalic or isophthalic acid to tereph-thalic acid (90-95%) 2,2 -biphenyldicarboxylic acid to 4,4 -biphenyldicarboxylic acid 3,4-pyrroledicarboxylic acid to 2,5-pyr-roledicarboxylic acid and 2,3-pyridinedicarboxylic acid to 2,5-pyridinedicarboxylic acid. A closely related method for preparing aromatic dicarboxylic acids is the thermal disproportionation of the potassium salt of an aromatic monocarboxylic acid to an equimolar mixture of the corresponding aromatic hydrocarbon and the dipotassium salt of an aromatic dicarboxylic acid. The disproportionation method has been used to convert benzoic acid to terephthalic acid (90-95%) pyridine-carboxylic acids to 2,5-pyridinedicarboxylic acid (30-50%) 2-furoic acid to 2,5-furandicarboxylic acid 2-thiophenecar-boxylic acid to 2,5-thiophenedicarboxylic acid and 2-quinoline-carboxylic acid to 2,4-quinolinedicarboxylic acid. One or the other of these two methods is often the best way to make otherwise inaccessible aromatic dicarboxylic acids. The two methods were recently reviewed. ... 

Sulfur compounds have also been widely studied as activating agents for polyesterification reactions. p-Toluenesulfonyl chloride (tosyl chloride) reacts with DMF in pyridine to form a Vilsmeir adduct which easily reacts with carboxylic acids at 100-120° C, giving highly reactive mixed carboxylic-sulfonic anhydrides.312 The reaction is efficient both for aromatic dicarboxylic acid-bisphenol312 and hydroxybenzoic acid314 polyesterifications (Scheme 2.31). The formation of phenyl tosylates as significant side products of this reaction has been reported.315... 

The dimethylbenzenes (xylenes) are very important industrial chemicals recovered during the refining of petroleum. All three xylenes are used to produce the corresponding aromatic dicarboxylic acids by reaction with oxygen over a catalyst. 

Synthesis of polyanhydrides from the aromatic dicarboxylic acids (isophthalic and terephthalic acids) by melt polycondensation was first... 

For example, such attempts were undertaken in a body of work [60] dealing with the preparation (through acceptor-catalytic copolyesterification) of triple copolyesters composed from the residues of aromatic dicarboxylic acids, bisphenols and N-methyldielhanolamine (NMDEA). Scheme 7 illustrates the principle of such a syntheses the upper part shows the chemical... 

Wick, G. and Zeitler, H., Cyclic oligomers in polyesters from diols and aromatic dicarboxylic acids, Angew. Makromol. Chem., 112, 59 (1983). 

As the aromatic dicarboxylic acid BB has a much more rigid structure than Cl-PEC, the Tgs of the LCPs derived from BB are supposed to be much higher than those derived from Cl-PEC. Although, in the case of LCPs derived from BB, it is difficult to detect the Tg values by DSC measurements, these values have good correlation with the E"(max) parameters determined by dynamic mechanical analysis (Figure 19.11). According to this study, the Tg of Me-HQ/BB was... 

In our previous article (14) the gelation in the polymerization of diallyl aromatic dicarboxylates has been experimentally examined in detail and discussed according to Gordon s theory (15). The discrepancy between actual and theoretical gel point conversion was quite large. In this connection, the gelation behavior of glycol bis(allyl phthalate)s was explored in detail from both experimental and theoretical standpoints. 

Uses Solvent used in organic synthesis, paint removers, plastics, resins, gums, and electrolytes chemical intermediate catalyst extracting agent for gases and oils purifying and crystallizing aromatic dicarboxylic acids. 

The phthalic acids are examples of aromatic dicarboxylic acids. 

The technical production of poly(benzimidazole) (PBI) is also carried out in two steps. In the first step an aromatic tetramine is condensed with the diphenyl ester of an aromatic dicarboxylic acid at 220-260 °C, yielding a poly(amino amid) with elimination of phenol. Ring closure with elimination of water occurs in the second step (solid-phase polycyclocondensation), conducted at 400 °C and yielding the polybenzimidazole (experimental procedure, see Table 2.3). 

Polyarylates (PAr) are wholly aromatic polyesters derived from aromatic dicarboxylic acids and diphenols or their derivatives. They are amorphous in nature with good injection moldability. Figure 7 shows the typical formula structure of PAr. 

The diacid components for the manufacture of poly( -phenyleneisophthalamide) and poly( -phenyleneterephthalamide) are produced by one of two processes. In the first, the diacid chlorides are produced by the oxidation of >% -xylene [108-38-3] orxylene [106 -2-3] followed by the reaction of the diacids with phosgene [75-44-5]. In the second, process m- or p-xylene reacts with chlorine initiated by ultraviolet light to form the m- or % he x achl o r o xylene. This then reacts with the respective aromatic dicarboxylic acid to form the diacid chloride. 

Liquid crystal polyesters are made by a different route. Because they are phenolic esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavorable reactivities. The usual method is the so-called reverse ester exchange or acidolysis reaction (96) where the phenolic hydroxyl groups are acylated with a lower aliphatic acid anhydride, eg, acetic or propionic anhydride, and the acetate or propionate ester is heated with an aromatic dicarboxylic acid, sometimes in the presence of a catalyst. The phenolic polyester forms readily as the volatile lower acid distills from the reaction mixture. Many liquid crystal polymers are derived formally from hydroxyacids (97,98) and their acetates readily undeigo self-condensation in the melt, stoichiometric balance being automatically obtained. 

A number of aromatic dicarboxylate esters were also found to undergo allylation with loss of the silyl group when photolyzed in the presence of allyltrimethylsilane in acetonitrile-methanol175. As illustrated in equation 35 the naphthalene dicarboxylate 339 evidently underwent allylation, but then subsequently underwent photochemical [2 + 2] cycloaddition to give the polycyclic product 340 in other cases the reaction stopped after allylation. 

Benzenoid hydrocarbons, which like perylene (10) contain a peripheral cisoid C4 arrangement (a bay region [71]), react with maleic anhydride in the presence of a suitable dehydrogenating agent to form fully aromatic dicarboxylic acid anhydrides 12 ( benzogenic Diels-Alder reaction ) [72, 73], Since in this process the ratedetermining step is the exocyclic Diels-Alder reaction leading to 11, the reactivity behaviour of the system is dominated by the Jt-electronic properties of the hydrocarbon centres at which this primary reaction occurs [74]. 

Two other minor products formed in the pyrolysis, not present in the starting benzothiophene, were phenylthiophene and bithienyl. According to our proposed scheme, these seem to demand the formation of thiophyne and/or thiophene from benzothiophene. Mass spectra of some aromatic dicarboxylic anhydrides give a clue to a possible mechanism. 

A single-step preparation of a new class of soluble co- and terpoly(arylene-oxadia-zole) polymers containing at least 20 repeat units have been prepared by the condensation of aromatic dicarboxylic acids with hydrazine hydro-chloride. Photoluminescence efficiencies of 50% were reported. Targeted applications include electroluminescent devices, photovoltaics, and diodes. 

Crystallization and Purification Solvent. Dimethylacetamide is useful in the purification by crystallization of aromatic dicarboxylic acids such as terephtlialic acid [100-21-0] andc arb o xyphenylacetic acid [501-89-3]. These acids are not soluble in the more common solvents. DAIAC and dibasic acids form crystalline complexes containing two moles of the solvent for each mole of acid (16). Alicrocrystalline hydrocortisone acetate [50-03-3] having low settling rate is prepared by crystallization from an aqueous DAIAC solution (17). 

The kinetic treatment revealed that the reactivity of pendant allyl groups of the prepolymer is approximately equal to that of the monomer. The ratios ri = kii/kii and r2 = kn/kn have been estimated to be 1.0 and 0.9, respectively [67]. A similar result was also observed for the post-copolymerization of DAI prepolymer with ABz [68]. Now, we can conclude that the concept of equal reactivity of functional groups belonging to the monomer and polymer is valid for the radical polymerization of diallyl aromatic dicarboxylates at an early stage of polymerization, at least up to the theoretical gel point. However, in the case of the highly branched prepolymer formed at a late stage of polymerization, i.e. far beyond the theoretical gel point, the reactivity of pendant allyl groups may be reduced by steric hindrance. 

The most important applications of peroxyacetic acid are the epoxi-dation [250, 251, 252, 254, 257, 258] and anti hydroxylation of double bonds [241, 252, the Dakin reaction of aldehydes [259, the Baeyer-Villiger reaction of ketones [148, 254, 258, 260, 261, 262] the oxidation of primary amines to nitroso [iJi] or nitrocompounds [253], of tertiary amines to amine oxides [i58, 263], of sulfides to sulfoxides and sulfones [264, 265], and of iodo compounds to iodoso or iodoxy compounds [266, 267] the degradation of alkynes [268] and diketones [269, 270, 271] to carboxylic acids and the oxidative opening of aromatic rings to aromatic dicarboxylic acids [256, 272, 271, 272,273, 274]. Occasionally, peroxyacetic acid is used for the dehydrogenation [275] and oxidation of aromatic compounds to quinones [249], of alcohols to ketones [276], of aldehyde acetals to carboxylic acids [277], and of lactams to imides [225,255]. The last two reactions are carried out in the presence of manganese salts. The oxidation of alcohols to ketones is catalyzed by chromium trioxide, and the role of peroxyacetic acid is to reoxidize the trivalent chromium [276]. 

Scheme 1. Melt polycondensation of diaminobenzidine with aromatic dicarboxylic acid esters...

Another versatile pathway to acid iodides was described by Hoffmann (equation 13). Aliphatic and aromatic acid iodides are prepared in high yields from acid chlorides by reaction with sodium iodide in acetonitrile. A large number of alkanoyl, alkenoyl and aroyl iodides can be prepared in good yields from the corresponding acid chlorides. In the same way it was possible for the first time to obtain diiodides from aliphatic and aromatic dicarboxylic acids. The conversion of acid chlorides to iodides by sodium iodide had been known before the reaction conditions proposed by Hoffmann, however, are milder and the yields are higher. 

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