| Abstract
| - The enthalpies of formation in the condensed and gas states, ΔfH°m(cd) and ΔfH°m(g), of 1,3- and 1,4-oxathiane sulfones were derived from their respective enthalpies of combustion in oxygen, measured bya rotating bomb calorimeter and the variation of vapor pressures with temperatures determined by theKnudsen effusion technique. Standard ab initio molecular orbital calculations at the G2(MP2) and G3levels were performed, and a theoretical study on molecular and electronic structure of the compoundshas been carried out. Calculated ΔfH°m(g) values at the G3 level using atomization reactions agree wellwith the experimental ones. These experimental and theoretical studies support that the destabilizationfound in 1,3-oxathiane sulfone, 11.2 kJ mol-1 respecting to 1,4-oxathiane sulfone, is due to the electrostaticrepulsion between the negative charges of the axial oxygen of the sulfone and the oxygen of the ring andapparently masks any stabilization originating from the hyperconjugative nO → σ*C-SO2 stereoelectronicinteraction.
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