Ethylene Glycol → 4,4'-(1,3-Dioxolane-2,2-diyl)diphenol

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Reaction Steps

2,2-bis(4-hydroxyphenyl)-1,3-dioxolane was prepared by the procedure of Example 5 by mixing together, in a reaction flask fitted with a mechanical stirrer, thermometer, and variable take-off distillation head, 99 gm of 4,4'-dihydroxybenzophenone (97% pure, 0.448 mole), 269 gm of ethylene glycol (4.3 moles), 96 gm of trimethyl orthoformate (0.91 mole), and 150 gm of montmorillonite clay (K-10, United Catalysts) and heating the reaction mixture at 70° to 90° to give slow distillation of the reaction by-products. After about 18 hours, 66 gm of distillate had been collected, an additional 64 gm of trimethylorthoformate (0.60 mole) was added to the reaction mixture, and the reaction continued. After a total of 24 hours reaction time, NMR analysis of a reaction sample showed about 2.23 mole ratio of ketal product to ketone starting material; after a total of 48 hours reaction time, NMR analysis of a second reaction sample showed the mole ratio was about 19 (about 95% conversion to ketal product). The reaction mixture was heated for an additional 8 hours and then cooled; NMR analysis again showed about 95% conversion.

Provenance & Evidence