NMR Subspectral Analysis Applied to Polyfluorobenzenes C6HnF6—n. I. 1,2,3,5-Tetrafluorobenzene

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Abstract
The nuclear magnetic resonance spectrum (1H and 19F) of 1,2,3,5‐tetrafluorobenzene is described. All coupling constants are obtained by subspectral analysis applicable to an AA′XX′MR system. A perturbation treatment for the AA′XX′MY case is outlined and illustrated by the R(Y) part of the spectra of 1,2,3,5‐tetrafluorobenzene and pentafluorobenzene. The chemical shifts and the magnitude of coupling constants agree with values obtained for similar molecules. Also the result that the sign of J HF ortho is opposite to that of J HF para is in accord with earlier findings. It is emphasized that HF and FF coupling constants follow a monotonic sequence from J ortho through J meta to J para.