The orientation and sign-dependence of 4-bond fluorine–fluorine coupling constants
- 1 January 1969
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society B: Physical Organic
- p. 1022-1023
- https://doi.org/10.1039/j29690001022
Abstract
An analysis of the reported 4J(F–F) couplings in perfluoromethylcyclohexane and some fluorinated propanes enables the magnitudes and signs of all the 4J(F–F) couplings in heavily fluorinated C·C·C fragments to be obtained. These are Jtt(trans-trans)–10, Jtg(trans-gauche)ca. 0, Jgg(gauche-gauche)+16; and Je(eclipsed)+26 Hz. The noteworthy predictions from these results are that 4J(F–F) couplings can be of either sign in the same molecule and that the large F–F couplings observed when two fluorine atoms are in close proximity are probably always positive.Keywords
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