Quantitative aspects of Lewis acidity. Part VI. Boron trifluoride–aniline equilibria in ether

Abstract

In ether solution boron trifluoride and substituted anilines interact initially to give 1 : 1 co-ordination adducts, which may subsequently disproportionate to yield anilinium tetrafluoroborates and arylaminoboron difluorides. Equilibrium constants, K, for the initial 1 : 1 adduct formation are reported. o-Methyl and o-chloro substituents hinder adduct formation. For unhindered bases at 25° pK=–0·96 pK_a–0·29, where K_a is the dissociation constant of the corresponding anilinium ion in water. The ultraviolet spectra of the adducts in ether very closely resemble those of the corresponding anilinium ions in a similar solvent.