Analysis of NMR line shapes of rigid-lattice multispin systems. V. 19F shielding tensors of CF3 groups bonded to carbon

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The fluorine chemical shielding tensors, CF3 group geometries, and fluorine spin-rotation tensors in CF3CN, CF3CCl3, CF3COOD, and CF3CD2OD are determined from rigid-lattice 19F NMR line shapes for these molecules incorporated in glass matrices. In contrast to the variability shown by trifluoromethyl halides, the shielding components hardly vary with the substituents on the α carbon atom. Shielding is largest parallel to the CF bond and least perpendicular to C–F in the CCF plane. The full tensors agree fairly well with the partially defined tensors of similar molecules given by liquid crystal studies but they are far from being axially symmetric about the CF bonds.