A study of the stable conformations of methylvinyl sulfoxide and sulfone by ab initio calculations

The potential energy curves for the C-S torsion of methylvinyl sulfoxide and sulfone were calculated using ab initio methods (RHF/3-21G∗ and MP2/6-31G∗). In both cases two minima were found. In the case of methylvinyl sulfoxide the most stable conformation has the SO group cis to the double bond. The other stable conformation has the lone-pair electrons of the sulfur atom cis to the double bond. The energy difference between the two minima is 8–16 kJ mol−1 depending on the method used. In methylvinyl sulfone there are two equivalent minima with the SO group cis to the double bond.