Ionic equilibria of tris-arylmethyl systems

Abstract

The constants governing the equilibrium between the carbonium ions (I), (11) and (111), R = Hand p-or m-phenyl-, and the corresponding carbinols have been measured in formic acid solution at 20", and values of the appropriate acidity function HR have been derived for this medium containing added sodium formate or sulphuric acid. The relative stabilities of the tris-arylcarbonium ions are shown to be dependent upon, not only their n-electron delocalization energies, but also their solvation energies. The factors governing other tris-arylmethyl equilibria are discussed.The tris-arylmethyl chlorides dissociate in liquid sulphur dioxide,z or in chloroor nitro-hydrocarbons,2 to give the corresponding ion-pair and the free chloride and tris-arylcarbonium ion, ktz kb Ar,CCl+(Ar,C+Cl-)+Ar,C+ + Ci-. (1) Conductivity measurements give, for the sulphur dioxide solutions,l the dissociation constant Kexpt where [Ar,C+] [Cl-] -K b K e x p t = [Ar,CCI] + [(Ar,C+Cl-)]and values of the corresponding free energy of dissociation ( AGexpt = -RT in Kexpt)