Nuclear magnetic resonance studies of some fluorinated pyridines oriented in nematic phases

The n.m.r. spectra of 2,3,5,6-tetrafluoropyridine, perfluoro(4-methylpyridine) and 3,5-dichloro-2,4,6-trifluoropyridine oriented in nematic phases have been accurately analysed and structural data obtained. In the case of perfluoro(4-methylpyridine) the rotation of the CF3 group, whilst being assumed to be faster than the reorientational motion of the molecules in the nematic phase, is internally restricted with the staggered rotamers being energetically preferred.The average orientations of these solute molecules are compared with those of other substituted pyridines.