FLUORINE-19 NUCLEAR MAGNETIC RESONANCE SPECTRUM OF PARA-BONDED HEXAFLUOROBENZENE

The six-spin AA′XX′X″X‴ system of hexafluoro 'Dewar' benzene has been analysed and values for all the F,F-coupling constants have thereby been obtained. The 19F n.m.r. spectrum consists of two complex groups of bands, one due to vinylic fluorines (φ* 122.8 p.p.m.) and the other to bridge fluorines (φ* 191.0). A calculated spectrum has been fitted to the experimental one and the following values of the coupling constants have been found: JAX ±9.92, J′AX ±7.12, JAA ±9.36, JXX ±0.10, J′XX ±14.03, and J″XX ±3.01 c./sec. Assignments of these coupling constants are discussed.