THE DETERMINATION OF LOCAL-STRUCTURE IN ORGANOFLUORIDES USING F-19 C-13 DIPOLAR COUPLING

H-1-F-19-C-13 double cross polarization (DCP)/magic angle spinning (MAS) C-13 n.m.r. and C-13-F-19 rotational echo double resonance (REDOR) CP/MAS C-13 n.m.r. experiments performed on two low-molecular-weight monofluorinated organic compounds are reported. DCP n.m.r. permits the selective identification of resonances of carbons one- and two-bonds removed from a fluorine atom in these substances. Under our experimental conditions the F-19 T2 is on the order of 1 ms or less. This relaxation process is beneficial in the DCP experiment. It defeats proper echo formation in C-13-F-19 REDOR CP/MAS C-13 n.m.r. experiments in which MAS speed and F-19(T2)-1 are comparable. Potential remains for REDOR in coal structure analysis under experimental conditions that result in lengthened F-19 T2.