Sulfonation chemistry of some small molecule models of EPDM rubbers. II. The structure of intermediate adducts

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Abstract
As previously reported, our initial investigation was concerned with the bicyclic olefins, ethylidene norbornane, and dihydrodicyclopentadiene. The former produced a skeletally rearranged γ‐sultone and the latter an allylic sulfonic acid. In an attempt to further clarify the mechanisms of the sulfonation of these two models and to extend the study to models of other types of EPDM, we have now examined the sulfonation of several other model olefins. In addition to the bicyclic olefins reported previously, we have studied the sulfonation of monocyclic type II and III olefins and cyclic type I and type II olefins. The results showed that the bicyclic olefins behaved differently from their monocyclic analogs reinforcing earlier speculation as to a synchronous reaction mechanism. Exocyclics gave allylic sulfonic acids while endocyclics produced β‐sultones, which is the exact reverse of what was observed for the bicyclic counterparts. Acyclic type II olefins produced “stable” β‐sultones, and the influence of the sulfonating reagent on the subsequent chemistry is discussed. Type I olefins, curiously, gave a complex mixture of initial products which tended to rearrange to essentially a single thermodynamic product. The results of the investigation suggest that based on these models, each of the three major types of EPDM should have a different sulfonation mechanism.