Anomalous Melt Condensation Behavior of Pure Isomers of Protocatechuic Acid Derivatives

Abstract

Separation of a mixture of regio isomers of 6- and 7-carboxy-2-hydroxymethyl-1,4-benzodioxane (1) was successfully carried out by the fractional crystallization of their acetyl derivatives. Pure 1a (or 1b) gave an infusible product upon heating at 280 °C for 90 (or 30) min under reduced pressure, while a mixture of the regio isomers 1a and 1b polymerized to yield a high-molecular-weight spinnable polyester under the same conditions.