Benzene dicarboxylic acid, aromatic

One super fiber is Kevlar, an aromatic polyamide. It is a polymer of 1,4-benzene-dicarboxylic acid and 1,4-diaminobenzene. Aromatic polyamides are called aramides. 

Aramids are formed through step growth polymerization of aromatic diacid chlorides with aromatic diamines in a polar aprotic solvent such as N, -dimethylformamide pMF) to a DP of 100-250. The meta- and para-substi-tuted benzene dicarboxylic acid chlorides and diamines are characteristically used for aramid fibers presently in production, but other fully aromatic ring systems are possible future sources of aramid polymers for fi bers ... 

The aromatic acids, as you would suspect from the name, have a benzene ring connected directly to the carboxyl signature group. Dicarboxylic acids have carbo l, groups attached in two places. Monocarboxylic adds have only one, and of course, the poly acids have three or more.. ... 

Reactions of 4,7-phenanthroline-5,6-dione have been the subject of considerable study. It is reduced to 5,6-dihydroxy-4,7-phenanthroline by Raney nickel hydrogenation226,249 or by aromatic thiols in benzene,262 and oxidized by permanganate to 3,3 -bipyridyl-2,2 -dicarboxylic acid.263 It forms bishemiketals with alcohols226 and diepoxides with diazomethane.226 The diepoxides by reaction with hydrochloric acid form diols of type 57, R = Cl, which on oxidation with lead tetraacetate give 3,3 -bipyridyl diketones of type 58, R = Cl. Methyl ketones of type 58, R = H, are also obtained by lead(IV) acetate oxidation of the diol 57, R = H, obtained by lithium aluminum hydride reduction of 57, R = Cl. With phenyldiazomethane and diphenyldiazomethane the dione forms 1,3-dioxole derivatives,264,265 which readily hydrolyze back to the dione with concomitant formation of benzaldehyde and benzophenone, respectively. 

Friedel-Crafts Acylation, The Friedel-Crafts acylation procedure is the most important method for preparing aromatic ketones and their derivatives. Acetyl chloride (acetic anhydride) reacts with benzene in the presence of aluminum chloride or acid catalysts to produce acetophenone [98-86-2], CgHgO (1-phenylethanone). Benzene can also be condensed with dicarboxylic acid anhydrides to yield benzoyl derivatives of carboxylic acids. These benzoyl derivatives are often used for constructing polycyclic molecules (Haworth reaction). For example, benzene reacts with succinic anhydride in the presence of aluminum chloride to produce p-benzoylpropionic acid [2051-95-8] which is converted into a-tetralone [529-34-0] (30). 

Exercise 29-31 Fibers made from aromatic polyamides such as from 1,4-benzene-dicarboxyl ic acid and 1,4-benzenediamine are at least as strong as steel wire with the same ratio of weight to length. What are the structural features of this kind of polyamide that contribute to the strength ... 

Oxidation of aromatic systems containing alkyl side-chains results in the formation of a carboxylic acid, irrespective of the length of the side-chain. The usual oxidizing agents are potassium permanganate [potassium manganate(VII)] or chromic acid [chromium(VI) acid]. For example, 1,4-dimethylbenzene is oxidized to benzene-1,4-dicarboxylic acid (tereph-thalic acid, 9), an important building block for polyesters. The oxidation of isopropylbenzene (cumene) to phenol is an important industrial process and is discussed in Chapter 4. 

Electrophilic reagents preferentially attack benzimidazoles in the fused benzene ring, while nucleophiles react at C-2 which has enhanced nucleophilic activity because of the electron-withdrawal effect of the benzene moiety. The fused aryl ring appears to exhibit less aromatic stability than the heteroring as evidenced by the ready oxidation of benzimidazole to imidazole-4,5-dicarboxylic acid, and by its catalytic reduction over platinum... 

Synonyms Benzene-1,4-dicarboxylic acid 1,4-Benzenedicarboxylic acid p-Benzenedicarboxylic acid Benzene-p-dicarboxylic acid p-Dicarboxybenzene p-Phthalic acid PTA TPA Classification Aromatic dicarboxylic acid Empirical CsHsO,... 

Synonyms Acetonedicarboxylic acid Acetone-1,3-dicarboxylic acid ADA Empirical CsHeOs Formula HOOCCH2CH2COCOOH Properties Colorless needles sol. in water, alcohol insol. in benzene, chloroform, chlorinated and aromatic soivs. m.p. 135 C (dec.)... 

Attempts had been made to synthesise polyesters based on phthalic acid as the diacid component, but these products were amorphous, had low softening points, and were rapidly attacked by organic solvents and acids and bases. Research into polyesters made by the reaction of terephthalic acid (or esters thereof) with aliphatic diols, led to the discovery of polyesters of high commercial value poly(alkylene terephthalate)s [4]. This pairing of diols with terephthalic acid eventually led to the most commercially successful aromatic polyesters, but other synthetic pathways were also investigated towards such products in the early days of polyester development. These included the self-condensation of hydroxy acids of the structure -H0-R-Ph-C02H, where R-OH is para to the acid group and R is -(CH2)- or -(CH2)2- [5], and reactions of aliphatic diacids with 1,4-dihydroxy benzene and similar aromatic diols [6, 7]. Also synthesised about the same time were polyesters based on C2-Cg aliphatic diols and any of the isomeric naphthalene dicarboxylic acids [8]. 

The simplest aromatic carboxylic acid is benzoic acid. Derivatives are named by using numbers and prefixes to show the presence and location of substituents relative to the carboxyl group. Certain aromatic carboxylic acids have common names by which they are more usually known. For example, 2-hydroxybenzoic acid is more often called salicylic acid, a name derived from the fact that this aromatic carboxylic acid was finst obtained from the bark of the willow, a tree of the genus SaEx. Aromatic dicarboxylic acids are named by adding the words dicarboxylic acid to benzene. Examples are 1,2-benzenedicarboxyhc acid and 1,4-benzenedicar-boxylic acid. Each is more usually known by its common name phthahc acid and terephthalic acid, respectively. Terephthahc acid is one of the two organic components required for the synthesis of the textile fiber known as Dacron polyester (Section 16.4B). 

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