Abstract: A fractional distillation method of separating diacetoxybutene isomers from a reaction mixture produced from the reaction of butadiene, acetic acid and molecular oxygen comprises employing a series of at least two distillation towers, one of said towers being used for distillation of water and acetic acid under a pressure of 30 - 250 Torr and a tower bottom temperature of 190.degree. - 120.degree. C and the other being used for separation of high boiling point materials under a pressure of 2 - 100 Torr and a tower bottom temperature of 190.degree. - 120.degree. C, the temperature of all tower bottoms being from 190.degree. - 120.degree. C.