The cis-trans Isomerization of 2-Butenes Caused by Sulfur Dioxide Adsorbed on Porous Vycor Glass. The Contribution of the Charge-transfer Complex

Sulfur dioxide adsorbed on porous Vycor glass enhances the cis-trans isomerization of 2-butenes selectively, but it poisons the double-bond migration. The correlation between the cis-trans isomerization and the sulfur dioxide–cis-2-butene charge-transfer complex observed on the glass were studied under various pressures of the reactants. The kinetic data of the reaction were well explained by the reaction mechanism in which the isomerization occurs via the addition and elimination of 2-butene molecules at the terminal of the polysulfone formed from sulfur dioxide and cis-2-butene in the adsorbed layer. It has been suggested that the copolymerization is initiated through the charge-transfer complex polarized in the strong electrostatic field of the exposed aluminum ions contained in the glass.