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