Backbone‐assisted reactions of polymers. V. Kinetics of isomerization of poly(chloromethylthiirane) and poly(3‐chlorothietane) in solution

The reversible isomerization of poly(chloromethylthiirane) and poly(3‐chlorothietane) represents a new kind of polymer reaction and a new method of copolymer synthesis. In chloroform, in dichloromethane, or in nitrobenzene the reaction is well described by reversible first‐order kinetics. A rate increase of ca. 40% on changing the solvent from chloroform to nitrobenzene is consistent with an isomerization mechanism that involves a rate‐determining attack of the backbone sulfur atom on the neighboring carbon‐chlorine bond and rapid ring‐opening of the thiiranium ion intermediate by chloride ion.