Fluorine magnetic resonance studies. I. para -Substituted β,β-difluorostyrenes

A series of seven para -substituted ß,ß-difluorostyrenes has been prepared and their proton and fluorine magnetic resonance spectra recorded. The fluorine spectra show interesting correlations with the s- values for the para substituents, the fluorine resonances moving to lower field and the geminal fluorine-fluorine coupling constant decreasing as s- increases. These trends parallel those observed in the analogous styrenes but rather more precise relationships have been established for the fluorine compounds. Long range fluorine-fluorine spin-spin coupling over six and seven bonds, respectively, has been observed in the ß,ß,ß,3- and ß,ß,4-trifluoro-styrenes.