A Study of Solid-State Anion Exchange between Some p -Aminophenol Hydrohalides and Twelve Alkali Halides by Infrared Spectroscopy

Abstract

The exchange of the anion of three hydrohalides of p-aminophenol and its N-methyl and N-benzyl derivatives has been studied by ir spectroscopy in Nujol mulls and pressed alkali halide disks. The vibrations involving the nitrogen atom are affected by the nature of the anion to an extent which makes it possible to detect the occurrence of exchange reactions. Normal grinding and pressing conditions can lead to complete exchange with the halide ion of the matrix material. The trend of exchange which is apparent for the organic compounds in sodium and potassium halides is reversed in rubidium and cesium halide matrix materials, and the presence of moisture in the grinding stage enhances the rate of reaction in most cases. Possible mechanisms are discussed in terms of the physical properties of the compounds involved, of which the main influencing factors appear to be the crystal type, lattice energies, relative ionic dimensions, and pressure induced transitions.