AbstractThe19F n.m.r. spectrum of hexafluoroquinazoline has been analyzed giving the signs and magnitudes of all but two of the coupling constants, and supporting the analyses of the19F n.m.r. spectra of heptafluoroquinoline and heptafluoroisoquinoline. Long range FF inter‐ring coupling constants are a guide for assessing π‐electron delocalization pathways. In addition, nitrogen in the β position enhances the distant F‐5, F‐7meta‐coupling constant, implying a π‐contribution toJ(FF)meta. A rationalization of changes inperi‐coupling constants is also presented. The observed changes appear to be the sum of two effects: (i) ring contraction by the insertion of shorter CN bonds into the aromatic ring and (ii) a secondary effect which is dependent on the existence of a β‐nitrogen, ad