Additivity of substituent effects upon proton–fluorine coupling constants in polysubstituted fluorobenzenes

Abstract

Substituent effects upon J_FH values in polysubstituted fluorobenzenes are demonstrated to be additive for the substituents F, Cl, Br, I, NO₂, NMe₂, and OMe. An evaluation of the substituent constants by a regression analysis allows the accurate calculation of 230 J_FH values in 70 compounds. The consequences of this analysis for the resolution of the ambiguities in the assignment of ³J_FH and ⁴J_FH values, and of the sign of ⁵J_FH in many reported J_FH values are discussed. The variation of the substituent constants with substituent electronegativity, E_X, are considered and an assessment of the literature reports of the correlation of J_FH with E_X is made.