Basic properties of cyclic sulphides and sulphoxides

Abstract

The pk_BH⁺ values of four-, five- and six-membered ring sulphides and sulphoxides have been estimated in aqueous sulphuric acid by using an n.m.r. technique. The protonation behaviours of tetrahydrothiophen and tetrahydrofuran have been compared. No appreciable influence of ring size on basicity has been found except in the case of thietan 1-oxide, which is observed to be less basic than the corresponding acyclic sulphoxide. The pK_BH+ values of the cis- and trans-4-t-butyl derivatives of the six-membered ring sulphoxide indicate that the oxygen atom of the SO group is more basic in the axial than in the equatorial position.