CRYSTAL AND MOLECULAR-STRUCTURES OF RING-SUBSTITUTED METHYL PHENYL SULFOXIDES - AN X-RAY AND MOLECULAR-ORBITAL ABINITIO INVESTIGATION

The solid-state crystal and molecular structure of a number of ring-substituted methyl phenyl sulfoxides, containing mainly fluorine substituents, has been obtained by X-ray analysis. The conformation found for the molecules has geometrical features very close to those of the most stable conformer(s) predicted by ab initio molecular orbital calculations. In those compounds without ortho substituents the S = O bond is only slightly twisted from being coplanar with the ring plane, while a larger twist is present when both ortho positions are substituted. In the presence of one ortho substituent the S = O bond adopts an anti orientation and is almost coplanar with the ring. With the unsymmetrically substituted derivatives two conformers are possible and in the case of ortho substitution the energy difference (18-24 kJ mol-1) is large enough to have crystals only of the lower energy conformer. When the ortho positions are both free, the energy difference is quite low (0.6 kJ mol-1) and both conformers are found in the same crystal.