5- isophthalic acid

The oxidation of m-xylene produces isophthalic acid. The reaction occurs in the liquid-phase in presence of ammonium sulfite  

Isophthalic acid s main use is for producing polyesters that are characterized hy a higher abrasion resistance than those using other phthalic acids. Polyesters from isophthalic acid are used for pressure molding applications. 

Ammoxidation of isophthalic acid produces isophthalonitrile. The reaction resemhles the one used for ammoxidation of phthalic anhydride  

Isophthalonitrile serves as a precursor for agricultural chemicals. It is readily hydrogenated to the corresponding diamine, which can form polyamides or he converted to isocyanates for polyurethanes. 

Roberts, R. and Khalaf, A., Friedel-Crafts Alkylation Chemistry, Marcel Dekker, Inc. New York, 1984, Chapter 2. 

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See also Isophthalic acid.) pHTHALIC ACID AND OTHERBENZENEPOLYCARBOXYLIC ACIDS] (Vol 18)... 

Like terephthalic acid, isophthalic acid is used as a raw material in the production of polyesters. Much of the isophthaUc acid is used for unsaturated polyesters, whereas terephthaUc acid is used almost exclusively in saturated (thermoplastic) polyesters. However, a considerable amount of isophthaUc acid is used as a minor comonomer in saturated polyesters, where the principal diacid is terephthaUc acid. The production volume of isophthaUc acid is less than 2% that of terephthahc. IsophthaUc acid was formerly produced in technical or cmde grades and only a small amount was purified. Now, however, it is all purified to a standard similar to that of terephthahc acid. 

Table 24. Physical Constants and Properties of Isophthalic Acid...

Exploiting the relative basicity of the xylene isomers, commercial units employ superacids, typically HE—BF, as the acid complexing agent for the separation of / -xylene (feedstock for isophthalic acid) (15). Amoco produces high purity / -xylene at its Texas City facility using the HE—BF process (see Btx processing). Similar processes can be used for the separation of high purity mesitylene and isodurene from their and C q isomers, respectively. 

Isophthalic acid (benzene-l,3-dicarboxylic acid) [121-91-5] M 166,1, m 345-348", pK 3.70, pK 4,60. Crystd from aqueous EtOH. 

Another amorphous terephthalate has also been introduced commercially. This is a copolymer based on 1,4-cyclohexylene glycol with a combination of terephthalic acid and isophthalic acid. The copolymer is claimed to have excellent optical properties, have low moulding shrinkage and be relatively easy to vaccum form. As with other terephthalates it is considered in more detail in Chapter 25. 

Isophthalic acid (m.p. 347°C), made by oxidation of /w-xylene, has also been introduced for resins. The resins have higher heat distortion temperatures and flexural moduli and better craze resistance. They are also useful in the preparation of resilient gel coats. 

Systems based on isophthalic acid often show better water and alkali resistance than those based on phthalic anhydride. This is not thought to be due to inherent differences between the phthalic and isophthalic structures but is ascribed to the fact that isophthalate resins have generally considerably higher viscosities which enable them to be diluted with greater amounts of styrene. It is the additional proportion of styrene which gives the improved water and alkali resistance. 

The process is also being increasingly modified by copolymerising with isophthalic acid (IPA) or cyclohexanedimethanol (CHDM) to improve clarity, toughness and harrier properties, properties of particular importance in bottle and film applications (see Section 25.5). 

In 1972 Eastman Kodak introduced a copolymer produced by reacting 1,4-cyclohexylene glycol with a mixture of isophthalic and terephthalic acids. Thus the polymer contains 1,4-cyclohexanedimethyloxy units (I), terephthalic acid units (II) and isophthalic acid units (III) Figure 25.20). 

One such material is the copolymer first marketed by the Japanese company Unitika in 1974 as U-Polymer and more recently by the Belgian company Solvay as Arylef and Union Carbide as Ardel. (Around 1986 the Union Carbide interest in Ardel, as well as in polysulphones, was taken over by Amoco.) Similar polyarylates have since been marketed by Hooker (Durel), Bayer (APE) and DuPont (Arylon). This is a copolyester of terephthalic acid, isophthalic acid and bis-phenol A in the ratio 1 1 2 Figure 25.23). 

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. ... 

Processes have been developed separating pure metaxylene from other Cj aromatics.Metaxylene is a raw material for the manufacture of isophthalic acid. The major outlets for the acid are in the synthesis of unsaturated polyester and alkyd resins, and for the production of isophthalic esters (plasticizers). 

Rauwolscine gives colour reactions like those of yohimbine and the absorption curves of the hydrochlorides of the two alkaloids are very similar. Heated to 300°/5 mm. rauwolscinic acid forms barman (p. 490) and 3-ethylindole and on fusion with potassium hydroxide decomposes into indole-2-carboxylic acid, isophthalic acid, barman and an unidentified indole derivative. Rauwolscine itself on distillation with zinc dust produces barman, 2-methylindole (scatole) and tsoquinoline. It is suggested that the alkaloid has the skeletal strueture suggested by Seholz (formula XIV, p. 508) for yohimbine, the positions of the hydroxyl and earbomethoxy grouf s being still imdetermined. 

Iso-phtalskure, /. isophthalic acid, -pikrin-skure, /. isopicric acid. 

Amino-2,4,6-triiodo-isophthalic acid Thionyl chloride DL-2-Acetoxypropionyl chloride 2-Amino-1,3-propanediol... 

Polymerizations of S and MMA with in situ catalyst formation have also been carried out. Matyjaszewski et a ..355 reported on the use of FeBr2 together with various ligands such as PfQHs). , NiCiIIo. and 133 alone or in combination. The use of diearboxylic acid (iminodiacetic acid, isophthalic acid)356 and methanimine ligands " for MMA polymerization has also been reported. 

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