HSAB analysis of charge transfer in the gas-phase acid-base equilibria of alkyl-substituted alcohols

Abstract

A simple model to analyze charge redistribution associated with proton transfer (PT) reaction is derived from a classical ion transport model. The model is applied to the gas-phase acid-base equilibria of alkyl alcohols. Proton transfer is simulated as the motion of a charged particle in an applied external potential defined by the chemical environment of the proton, and represented by the difference in proton affinity (PA) of the conjugated bases RO- and CH3O-; the latter is taken as reference. The electronic chemical potential of transfer accounts for both the amount and direction of charge transfer (CT). The relative acidity for a short series of alkyl alcohols is determined by the difference in proton affinity (ΔPA = PA(RO-) -PA(CH3O-)) of the conjugated bases. The predicted charge transfer is in agreement with the CT pattern obtained from the group hardness and electronegativity analysis. © 1999 American Chemical Society.