F-F coupling constants in some perfluoroalkyl-fluroaromatic compounds

Abstract

The ¹⁹F nuclear magnetic resonance spectra have been studied for the compounds perfluoro (2,4-di-isopropylquinonline)(I), perfluoro(4-isopropylpyridine)(II), 4-heptafluoro-isopropyl-2-methoxytrifluoropyridine (III), perfluoro(sec-butylbenzene)(IV) and perfluoro(4-sec-butylpyridine)(V). The spectral parameters are listed (including signs of some coupling constants) and discussed. Compounds (II)-(V) have large coupling constants originating from a “through-space” mechanism and these were shown to be opposite in sign from ortho J_FF. At –40° the spectra of the two rotational isomers of compound (III) were distinguished.