The ¹⁹F chemical shift in oxygen containing carbon fluorine products

Abstract

Abstract We have examined the 19 F NMR spectra of a number of oxygen‐containing fluorocarbon products and obtained a comprehensive set of 19 F chemical shift values, which enabled us to determine the influence of an oxygen atom bonded to a fluorocarbon group on the 19 F chemical shift. The influence of neighbouring fluorocarbon groups, either directly connected or separated by an oxygen atom, was also considered. Our results may be summarized as follows. An oxygen atom bonded by a single bond (ether type bond) to a fluorine substituted carbon atom decreases the 19 F chemical shift, as does the introduction of a further fluorine atom. Considering two adjacent fluorocarbon groups, a variation of x ppm in the 19 F chemical shift of one of the two groups gives a variation of 0·12 x ppm in the opposite sense on the 19 F chemical shift of the other group. If the two groups are connected by an ether oxygen atom, the effect is only about 0·06 x ppm.