Terephthalic benzene-1,4-dicarboxylic acid

If the MW is not m/z 166 and there is an intense ion at m/z. 149, this suggests an ester of a benzene dicarboxylic acid. If m/z 149 is the most intense ion, the mass spectrum represents a phthalate, where R is an ethyl group or larger (see Figure 28.1). The most intense ions in the mass spectra of isophthalates and terephthalates are [M - OR]+. 

Phthalic acid (1,2-benzene dicarboxylic acid), isophthalic acid (1,3-benzene dicarboxylic acid), and terephthalic acid (1,4-benzene dicarboxylic acid) are made by the selective oxidation of the corresponding xylenes. Terephthalic acid may also be produced from the oxidation of naphthalene and by the hydrolysis of terephthalonitrile. 

SYNS 1,4-BENZENE DICARBOXYLIC ACID DIMETHYL ESTER (9CI) DIMETHYL-1,4-BENZENE DICARBOXYLATE METHYL-4-CARBOMETHOXY BENZOATE NCI-C50055 TEREPHTHALIC ACID METHYL ESTER... 

The condensation polymer made by reacting ethylene glycol with 1,4-benzene dicarboxylic acid (terephthalic acid) produces a polymer that is almost exclusively converted into the fiber Dacron. The polymerization is run as an ester interchange reaction using the methyl ester of terephthalic acid ... 

Terephthalic acid, also called paraphthalic acid or 1,4-benzene dicarboxylic acid,... 

Terephthalate polyester ter- o(f)- tha lat, pa-le- es-tor n. Any polymeric ester of ter-ephthalic acid (1,4-benzene dicarboxylic acid), but in particular the three commercially important thermoplastic resins, polyethylene terephthalate, polybutylene terephthalate, and poly-cyclohexylene dimethylene terephthalate. 

Terephthalic acid ter-o(f)- tha-lik a-sod [ISV terebene, mixture of terpenes from distilled turpentine + phthalic acid] (1857) (TPA, paraphthalic acid, benzene-p-dicarboxylic acid) n. C6H4(COOH)2. White crystals or powder, used in the production of alkyd resins and thermoplastic polyesters. Mol wt, 166.13, sublimes above 300°C without melting. Syn p-phthalic acid, p-benzene-dicarboxylic acid. 

Bowen [148] obtained crystalline acrylic monomers, thus making it possible to purify them. By the reaction of 2-hydroxyethyl methacrylate with the three isomers of benzene dicarboxylic acid—phthalic, isophthalic, and terephthalic acid—adequate esters are obtained mixed in various proportions, these make an eutectic ternary mixture that can play the role of the organic phase in DARs. The only shortcoming of these monomers is that they show a tendency to acquire color in the presence of the polymerization accelerators (N,N-dimethyl-p-toluidine). Isomer dimethacrylates (o-, m-, and p-)bis(hydroxyethyl)-dihydroxybenzen-... 

Two important commercial diacids are adipic acid (hexanedioic acid) and tere-phthalic acid (benzene-1,4-dicarboxylic acid). Adipic acid is used in making nylon 66, and terephthalic acid is used to make polyesters. The industrial synthesis of adipic acid uses benzene as the starting material. Benzene is hydrogenated to cyclohexane, whose oxidation (using a cobalt/acetic acid catalyst) gives adipic acid. Terephthalic acid is produced by the direct oxidation of para-xylene in acetic acid using a cobalt-molybdenum catalyst. 

Terephthalic acid (benzene-1,4-dicarboxylic acid) [100-21-0] M 166.1, m sublimes >300" without melting, pKf 3.4, pKf 434. Purify the acid v/a the sodium salt which, after crystallisation from water, is re-converted to the acid by acidification with mineral acid. Filter off the solid, wash it with H2O and dry it in a vacuum. The S-benzylisothiuronium salt has m 204° (from aqueous EtOH). [Beilstein 9 IV 3301.]... 

Benzenedicarboxylic acids have trivial names. Benzene-1,4-dicarboxylic acid (terephthalic acid, 3) is used in the manufacture of commercially important polyesters. Esters of benzene-1,2-dicarboxylic acid (phthalic acid) are used for plasticizing polymers. 

Para-xylene may be oxidized to terephthalic acid by means of nitric acid. Liquid-phase oxidation of m- and p-xylene is complicated by the Increased resistance to oxidation of the second methyl group after the first has been oxidized to the carboxyl group. As a consequence of experience with this difficulty, development has been toward oxidation in, two steps, a flrst to the toluic acid stage and a second to the dicarboxylic acid. Esterification of the first carboxyl group results in much easier oxidation of the coond methyl to a carboxyl group. Other p-substituted benzenes such as p-diisopropylbenzene are oxidized by air in the presence of a cobalt catalyst to terephthalic acid. Use is made of this in a recent new approach which permits the use of catalyzed air oxidation of p-xylene and results in formation of dimethyl terephthalate. A four-step process has attained commercial importance air oxidation of p-xylene to toluic acid using oil- Oluble catalysts of cobalt or manganese, esterification with methanol to methyl p-toluate, a second air oxidation to monomethyl terephthalate, and Anally esterification with methanol to dimethyl terephthalate. 

Here, BDC is 1,4-benzene-dicarboxylate (terephthalic acid) and Zn40(BDC)3 represents the MOF-5 imit composition. The reaction equilibrium can be shifted toward formation of the MOF product by tuning the concentration profiles of the solvent, the water released, or the nitrate ions produced. Since esterification reactions can be driven in both directions without difficulty, it appears evident that the stability of MOF materials in applications could depend on polar protic environments and pH values (128). 

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). 

The first polyester, developed in the 1940s, involved the polymerization of benzene 1,4-dicarboxylic acid (terephthalic acid) with 1,2-ethanediol (ethylene glycol) to give poly-(ethylene terephthalate), abbreviated PET. Virtually aU PET is now made from the dimethyl ester of terephthahc acid by the following transesterification reaction (Section 14.4C) ... 

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