1,4-benzene-dicarboxylate

We can obtain different polymers with different properties if we carry out condensation polymerisation reactions between other monomer molecules. For example, if we react ethane- 1,2-diol with benzene-1,4-dicarboxylic acid, then we produce a polymer called Terylene. 

Terephthalic acid (benzene 1,4-dicarboxylate, TPA) and isophthalic acid (benzene 1,3-dicarboxylate, IPA) are reactive bi-functional acids used as monomers to make plastics and coatings. TPA is a starting material for polyethylene terephthalate (PET). TPA and IPA are used to make polyester lacquers and coatings including the internal coatings of food cans. 

A very recent and exciting example of a 3-D coordination polymers can found in the work of Ferey et al,25 on the use of trinuclear chromium clusters in combination with benzene-1,4-dicarboxylic acid. This reaction yields porous structures with unit cells volumes of up to 700 000 A3, i.e. similar to that of a small protein In the absence of single crystals for structure determination, the structures were solved by the ingenious use of Monte Carlo simulations with simulated annealing. 

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. 

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. 

The acidity of substituted benzoic acids is dependent on the relative ability of the substituent to donate or withdraw electron density. The more strongly a group withdraws electrons, the greater is the acidity. Thus the order of increasing acid strength is 4-hydroxybenzoic acid < benzene-1,4-dicarboxylic acid < 4-acetyl-benzoic acid < 4-cyanobenzoic acid... 

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. 

Suggest how the solid state structure of benzene-1,4-dicarboxylic acid is affected by hydrogen bonding. 

Benzene-1,3-dicarboxylic acid. See Isophthalic acid Benzene-1,4-dicarboxylic acid 1,4-Benzenedicarboxylic acid. See... 

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