RELATIVE NUCLEOPHILICITY OF SOME COMMON NUCLEOPHILES TOWARD SULFONYL SULFUR . NUCLEOPHILE-CATALYZED HYDROLYSIS AND OTHER NUCLEOPHILIC SUBSTITUTION REACTIONS OF ARYL ALPHA-DISULFONES

The relative reactivity of nine common nucleophiles in a displacement reaction at sulfonyl sulfur (eq 2) in 60% dioxane has been determined from either kinetic data on their catalysis of the hydrolysis of aryl α-disulfones (2) or, in the case of primary and secondary amines and azide ion, from direct measurement of their rate of reaction with 2. These data for sulfonyl sulfur (Table VII) are compared in Table VIII with data for some of these same nucleophiles in an exactly analogous displacement at sulfinyl sulfur (eq 1). The substitution at sulfonyl sulfur shows an entirely different pattern of nucleophile reactivity (F− ≫ AcO− ≫ Cl− > Br− > H2O) than the one at sulfinyl sulfur (Br− > Cl− ≅ AcO− > F− ≫ H2O). Interpreted in terms of the theory of hard and soft acids and bases (HSAB) these results indicate that sulfonyl sulfur is a much harder electrophilic center than sulfinyl sulfur, exactly as HSAB would have predicted it should be. Comparison of the data for sulfonyl sulfur with analogous data on nucleophilic reactivity in a substitution at another hard electrophilic center, carbonyl carbon (Table IX), reveals that the order of reactivity of the various nucleophiles toward sulfonyl sulfur (RNH2 > N3− > F− > NO2− > AcO−) is about the same as toward carbonyl carbon. © 1969, American Chemical Society. All rights reserved.