Roberta Fruttero, Donatella Boschi, Elisa Fornatto, Anna Serafino, Alberto Gasco and Otto Exner
Heterocyclic systems 3-furoxanyl, 4-furoxanyl and 3-furazanyl have been characterised as substituents by their substituent constants σm, σp, σI and σR, determined from pK and 19F NMR shifts: they are strongly electron attracting but weakly conjugated.