Solute descriptors for phenoxide anions and their use to establish correlations of rates of reaction of anions with iodomethane.
Partition coefficients from water to organic solvents for phenoxide anions have been obtained using a method based on the variation of pK(a) of phenols with solvent. From these partition coefficients, the Abraham descriptors for phenoxide anions, on the same scale as descriptors for neutral molecules, have been obtained. Equations have been constructed for the prediction of descriptors, and values of the Abraham descriptors E, S, A (equal to zero for the phenoxide anions we have studied), B, V, and J(-) have been determined or estimated for some 60 substituted phenoxide anions. These anions are characterized by very large values of the dipolarity/polarizability descriptor S and the hydrogen bond basicity descriptor B. In order to show the utility of the obtained phenoxide descriptors, we demonstrate that they can be combined with descriptors for carboxylate anions and permanent anions to yield equations for the Finkelstein reaction of anions with iodomethane in methanol, N,N-dimethylformamide, and water.
Abraham
Michael H
MH
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK. m.h.abraham@ucl.ac.uk
Acree
William E
WE