Effets de substituant sur la fréquence hydroxyle de phenols associés à des hydrocarbures benzéniques par liaison d'hydrogene

The electronic effects of X substituents in aromatic molecules XC₆H₅, XC₆H₄Me and XC₆H₄OMe are studied by measurements of the bonded OH frequencies of phenol-π-base complexes. A judicious choice of the experimental conditions (solvent, π-base concentration, phenol acidity, temperature) permits the following substituents to be studied: Me, Et, CH(Me)₂, OMe, OEt, OC₆H₅, NHMe, N(Me)₂, N(Et)₂, NHC₆H₅, C₆H₅, CHCH₂, CCH, CCMe, SMe, SC₆H₅, F, Cl, Br and I.Halogenated benzenes, benzotrichloride and benzotrifluoride were found to act solely as π-bases. Electronic effects are accurately measured by means of the linear combination ?₁σ₁ + ?_R?°_R. The ratio ?_R/?₁ shows that inductive and mesomeric effects are of the same importance. This ratio may be considered as an argument in favour of the symmetric configuration of the complex. Electronic effects are found to be additive in disubstituted benzenes.