| Poly(ethylene terephathalate)(PET) is a linear saturated polyester. It is found wideapplications in fiber and non-fiber fields. For its high strength and rigidity, excellentthermal-resistance and dimension-stability, as well as the prominent chemical-resistance,PET has an outstanding allround performance. So it's widely used in electronics,mechanics, and vehicles industry.Ab initio theory was performed to study the reaction mechanism of the reaction ofterephthalic (TPA) and ethylene glycol (EG) with hydrochloric acid as catalyst. Thegeometric configurations of reactors, intermediates, transition states and products wereoptimized by Hartree-Fock method at 3-21g level. The energies of stationary points alongthe pathway were calculated at 3-21g level. Intermediates and transition states wereconfirmed by the results of vibrational analysis. The pathway was calculated by IRC.From the results of the reaction mechanism of the reaction of terephthalic and ethyleneglycol, we can see that the reaction of terephthalic and ethylene glycol is as follows:①1A+HCl→TS1→M1+Cl-②M1+2B→TS2→M2→TS3→M3+H2O③M3+Cl-→TS4→M+HClThe activation energies of the reaction are 1.26 kJ/mol,104.69 kJ/mol,217.80kJ/mol,82.64 kJ/mol respectively, which is in good agreement with experimental results,and lay the theoretical foundation for ulterior studying the esterification of terephthalicand ethylene glycol with acid as catalyst or auto-catalyst.
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