N.M.R. studies of 19F chemical shifts and coupling constants in cyclobutane derivatives

摘要: The 19F spectra of several substituted trifluorochlorocyclobutanes which commonly occur as mixtures two cis-trans isomers have been investigated. Substituents different bulkiness introduced to shift the conformational equilibrium puckering motion cyclobutane ring system. A complete assignment resonances was possible, based on chemical shifts and H-F coupling constants. Vicinal F-F constants investigated for a possible dependence dihedral angle ϕ. It is found that change sign twice 0 ⩽ gf 1>80°, being negative small large angles positive intermediate angles. investigations were fluorine with completely eliminated couplings by means noise decoupling.