Conformational preferences and barriers to internal rotation in fluorothioanisoles from long-range spinspin couplings, photoelectron spectroscopy, and semiempirical molecular orbital calculations

The conformational preferences and barriers to internal rotation about the S—C(phenyl) bond have been investigated for thioanisole and its 2-fluoro, 2,6- and 3,5-difluoro, and 2,3,5,6-tetrafluoro derivatives. Measurements of long-range spin–spin couplings between the methyl carbon and the para ring proton indicate that the 2-fluoro and 3,5-difluoro compounds prefer conformations with all heavy atoms coplanar. The 2,6-difluoro and …