1968 Volume 41 Issue 5 Pages 1154-1158
The effects of various metal compounds on the glycolysis of terephthalonitrile were studied in the presence of water at 185°C. The catalytically-active species were found to be metal ions. Their catalytic activities were correlated with the acid ionization constants, pKa, of metal ions. The active catalysts were limited to the metal ions with pKa values larger than 7. The study of the reaction mechanism suggests that, while one group of metal ions accelerates the formation of glycol and hydroxyl anions, the other involves catalytic acceleration through the coordination of metal ions. The metal ions with pKa values of less than 7 showed no catalytic activities. These results were interpreted in terms of the tendency of the metal ions to form too stable coordination intermediates. Most of these metal compounds also served to inhibit the reactions. For a series of salts derived from a given metal, the catalytic activities were found to decrease with a decrease in their solubilities in water. On the other hand, metal oxides and hydroxides had high catalytic activities.
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