SO2-catalyzed anionic copolymerization of oxiranes with cyclic anhydrides

Terpolymerization of Sulfur Dioxide with Oxiranes and Cyclic Anhydrides

“…Therefore, it is very probable that in the ternary systems studied the cyclic anhydrides are incorporated to the growing chain mainly as a result of the transesterification of the sulfite ion (Equation (2)), which as shown earlier [6] proceeds in high yield at 50 8C. The rate of this reaction has a great effect on the molar ratio of SAn to SO 2 m. u. in the terpolymers (X).…”

“…The reactions were carried out in glass pressure ampoules equipped with a rubber septum, seal and steel cap, according to a general procedure described elsewhere. [4,6,7] The yield of the products obtained was determined on the basis of 1 H NMR spectra of post-reaction mixtures upon distilling off the unreacted SO 2 and oxiranes under reduced pressure.…”

“…[5] We have found that sulfite anions undergo transesterification in the presence of succinic anhydride (SAn), which leads to the formation of a carboxylic ester unit and anion of mixed anhydride type terminated by a SO 2 moiety (Equation (2)). [6] One could expect that in a ternary system comprising oxiranes, SO 2 , and cyclic anhydrides the transesterification reaction may compete with the addition of the oxirane/SO 2 complex (Equation (1)) resulting in the formation of terpolymers composed of alkylene sulfite and alkylene carboxylate units.…”