Fluorine-19 nuclear magnetic resonance spectrum of para-bonded hexafluorobenzene

Abstract

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: J_AX±9·92, J′_AX±7·12, J_AA±9·36, J_XX±0·10, J′_XX±14·03, and J″_XX±3·01 c./sec. Assignments of these coupling constants are discussed.