Zinc terephthalate

Fig. 8 MOF-5,21 a porous cubic zinc terephthalate which is topologically analogous to Re03. Gray spheres denote carbon, red oxygen, and white hydrogen, with Zn04 tetrahedra in blue. Reproduced with permission. Copyright 1999, Macmillan Publishers Ltd.

MOF-5, whereas in (b) there are two different sorts of linear linkers, as in the diamine pillared zinc terephthalate of Dybtsev. Topology (c) is adopted by the terephthalate Sc2(02CCgH4C02)3. 

Figure 2.32 Examples of structures based on paddle wheel dimer units. In the copper trimesate HKUST-1, (top, left and right), dimeric copper units link four trimesate ligands into a three-dimensional framework, leaving the apical coordination site accessible to other ligands (such as water molecules). In the pillared layered zinc terephthalate of Dybtsev et al. porous planar zinc terephthalate sheets (shown) are linked via the diamine diazabicyclo-octane (N(C2H4)3N) coordinated at the apical sites.

Figure 3 Solid-state structures of archetypal MOFs containing simple exogenous ligands, (a) MOF-5 (CCDC deposition SAHYIK), a cubic zinc terephthalate. (b) The flexible iron terephthalate, MIL-53(Fe) lt (CCDC deposition POJTUE), in its hydrated, as-synthesized form, (c) HKUST-1 (CCDC deposition FIQCEN), a copper trimesate. Non-coordinated solvents and protons removed for clarity...

A recently reported effect in MOF chemistry, which might become of considerable importance, is the highly dynamic nature of the frameworks under conditions of LAG. For example, grinding of ZnO and terephthalic acid with water, DMF or methanol yields 1-D, 2-D, or 3-D forms of the zinc terephthalate polymer, respectively (Figure 12). Different forms were almost completely... 

Figure 12 Illustration of the dynamic nature of coordination polymers and open MOFs under mechanochemical milling conditions. Millmg with a suitable liquid phase leads to the formation of different open- and close-packed materials based on zinc terephthalate. Such high level of structural dynamics is not observed in analogous slurry experiments...

Loiseau T, Muguerra H, Ferey G, Haouas M, Taulelle F. Synthesis and structural characterization of a new open-framework zinc terephthalate Zn3(OH)2(bdc)2-2DEF, with infinite Zn-0/j-OH)-Zn chains. J Solid State Chem 2005 178 621-8. 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Esterification ofTerephthalicAcid. Esterification of terephthaUc acid is also used to produce dimethyl terephthalate commercially, although the amount made by this process has declined. Imperial Chemical Industries, Eastman Kodak, Amoco, Toray, Mitsubishi, and Mitsui Petrochemical have all developed processes. Esterification (qv) generally uses a large excess of methanol in a Hquid process at 250—300°C. The reaction proceeds rapidly without a catalyst, but metal catalysts such as zinc, molybdenum, antimony, and tin can be used. Conversion to dimethyl terephthalate is limited by equiHbrium, but yields of 96% have been reported (75,76). 

A PEIT of 50/50 (molar ratio) composition is synthesized by a two-step reaction sequence as follows. In the first step, 97.10 g (0.5 mol) dimethyl terephthalate (DMT), 97.10 g (0.5 mol) dimethyl isophthalate (DMI), 136.55 g (2.2 mol) 1,2-ethanediol, and zinc acetate dihydrate ester interchange catalyst (2.7 x 10 4% mass of the total amount of DMI and DMT mixture) are weighed into a threenecked flask fitted with a mechanical stirrer, a nitrogen inlet, and a condenser. The medium is stirred for 2.0-2.5 h at 180-210°C under nitrogen. Ninety-two percent of the theoretical amount of methanol is removed by distillation. In the second step, antimony acetate polycondensation catalyst and trimethyl phosphate thermal stabilizer (9.9 x 10-4 and 1.5 x 10 3% mass of the total amount of DMI... 

Polymer International 48,No.9, Sept. 1999, p.885-8 KINETICS OF GLYCOLYSIS OF POLYETHYLENE TEREPHTHALATE WITH ZINC CATALYST... 

Figure 4.1 Representation of the structure of MOF-5 (a) six carboxylic acid groups from terephthalic acid are connected to four Zn" cations to form a metal-organic elementary zinc carboxylate cluster (only...

Krumpolc, M. and Malek, J., Esterification of benzenecarboxylic acids with ethylene glycol, IV. Kinetics of the initial stage of polyesterification of terephthalic acid with ethylene glycol catalyzed by zinc oxide, Makromol. Chem., 171, 69-81 (1973). 

Chen, L.-W. and Chen, J.-W., Kinetics of diethylene glycol formation from bishydroxyethyl terephthalate with zinc catalyst in the preparation of polyethylene terephthalate),./. Appl. Polym. Sci, 75, 1229-1234 (2000). 

In the case of the esterification of the diacid, the reaction is self-catalyzed as the terephthalic acid acts as its own acid catalyst. The reverse reaction, the formation of TPA and EG from BHET is catalytic with regard to the usual metal oxides used to make PET, but is enhanced by either the presence of hydroxyl groups or protons. In the case of transesterification of dimethyl terephthalate with ethylene glycol, the reaction is catalytic, with a metal oxide needed to bring the reaction rate to commercial potential. The catalysts used to produce BHET are the same as those needed to depolymerize both the polymer to BHET and BHET to its simpler esters. Typically, titanium, manganese and zinc oxides are used for catalysts. 

Bis(2-hydroperoxy-2-propyl)benzene, 3535 1,4-Bis(2-hydroperoxy-2-propyl)benzene, 3536 B is(2-hydroxyethyl)methylphosphine, 2029 Bis(2-hydroxyethyl) terephthalate, 3520 Bis(hydroxylamine)zinc chloride, 4061 Bis(hydroxymethyl) peroxide, 0924... 

For emulsion tests, polyamide-coated terephthalate plastic plates are attached powder-side down by double-faced transparent tape strips to the undersurface of the lid of 9 x 1 cm Pyrex Petri dishes. The plates, 2x3 cm, are cut from standard 20 x 20 cm polyamide-terephthalate plates used for thin-layer chromatography. They are Polygram - Polyamide-6 UV254, procured from Macherey-Nagel and Co. through Brinkmann Instruments, Inc., Westbury, N.Y. As indicated, they contain a fluorophore (zinc silicate) activated by short-wave UV, but not active in the 360-nm range used herein. 

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