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1H, 13C and 19F NMR study of 8-fluoro- and 8,12-difluoro[2.2]metaparacyclophane and of 9-fluoro- and 9,14-difluoro-2,11-dithia[3.3]metaparacyclophane

✍ Scribed by Ludger Ernst; Kerstin Ibrom

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
237 KB
Volume
36
Category
Article
ISSN
0749-1581

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✦ Synopsis

The 1H, 13C and 19F NMR spectra of 9, 14-diÑuoro-2,11-dithia[3.3]metaparacyclophane, and 3F 2 , its 9-monoÑuoro derivative, 3F, and of 8,12-diÑuoro[2.2]metaparacyclophane, and its 8-monoÑuoro deriv-2F 2 , ative, 2F, were experimentally assigned as fully as possible. Two-dimensional shift correlation techniques (H,H-COSY, C,H-and F,H-HETCOR) were applied and experimental 1H and 13C chemical shifts were compared with those predicted by assuming additivity of substituent chemical shifts (SCS). The diÑuoro compounds and 2F 2 3F 2 occur as conformers with syn-and anti-orientations of the Ñuorine substituents. The 19F signals of undergo 3F

2 coalescence near 398 K (at 188 MHz) from which the barrier to syn/anti-interconversion is estimated as *Gt \ 77 kJ mol~1. The shorter bridges in increase *Gt to a lower limit of 89 kJ mol~1. A number of through-space J(F,C) 2F 2 and J(F,H) couplings were observed. The small magnitudes of the J(F,F) couplings in and (0.4È1.9 Hz) do 2F 2 3F 2 not allow their unambiguous classiÐcation as through-space interactions.

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