The fluorine NMR spectra of some trifluoro-oxiranes

Abstract

Fluorine chemical shifts and fluorine-fluorine coupling constants have been obtained for the chloro, bromo, iodo and trifluoromethyl derivatives of trifluoro-oxirane (trifluoro ethylene oxide). By double resonance experiments the coupling constants have been shown to have the same sign relationships as the corresponding olefins. The magnitudes of the coupling constants suggest that the carbon-carbon bond of the oxirane ring behaves aa if it has considerable double bond character. The low values of the fluorine-fluorine geminal coupling constants are indicative of a large negative Fermi contact contribution.