RING STRAIN EFFECTS ON THE INTERCONVERSION OF INTERMEDIATES IN THE REACTION OF ORGANIC SULFIDES WITH SINGLET OXYGEN

Ab initio methods are used to investigate ring strain effects on sulfi de-singlet oxygen reaction intermediates. The optimized persulfoxide a nd thiadioxirane structures derived from 3-, 4-, and 5-membered ring s ulfides showed minor albeit systematic changes in geometry. These pers ulfoxides and thiadioxiranes are best described as distorted tetrahedr al and trigonal bipyramidal in nature, respectively. We find that the persulfoxy sulfur becomes less sulfonium-ion-like in character with de creasing ring size. In addition, the persulfoxide and the thiadioxiran e are nearly isoenergetic in all cases and their interconversion barri ers are nearly identical. We speculate that the anticipated ring strai n effect in the persulfoxide is compensated for by a weaker sulfur-oxy gen interaction and the corresponding relaxation of the need to attain the energetically preferred tetrahedral geometry.