H-1, C-13 AND F-19 NMR-STUDY OF 8-FLUORO[2.2]METAPARACYCLOPHANE AND 8,12-DIFLUORO[2.2]METAPARACYCLOPHANE AND OF 9-FLUORO-2,11-DITHIA[3.3]METAPARACYCLOPHANE AND 9,14-DIFLUORO-2,11-DITHIA[3.3]METAPARACYCLOPHANE

The H-1, C-13 and F-19 NMR spectra of 9,14-difluoro-2,11-dithia[3.3]me taparacyclophane 3F(2), and its 9-monofluoro derivative, 3F, and of 8, 12-difluoro[2.2]metaparacyclophane, 2F(2),, and its 8-monofluoro deriv ative, 2F, were experimentally assigned as fully as possible. Two-dime nsional shift correlation techniques (H,H-COSY, C,H- and F,H-HETCOR) w ere applied and experimental H-1 and C-13 chemical shifts were compare d with those predicted by assuming additivity of substituent chemical shifts (SCS). The difluoro compounds 2F(2) and 3F(2) occur as conforme rs with syn- and anti-orientations of the fluorine substituents. The F -19 signals of 3F(2) undergo coalescence near 398 K (at 188 MHz) from which the barrier to syn/anti-interconversion is estimated as Delta G double dagger = 77 kJ mol(-1). The shorter bridges in 2F(2) increase D elta G double dagger to a lower limit of 89 kJ mol(-1). A number of th rough-space J(F,C) and J(F,H) couplings were observed. The small magni tudes of the J(F,F) couplings in 2F(2) and 3F(2) (0.4-1.9 Hz) do not a llow their unambiguous classification as through-space interactions.