Cationic species in strongly acid media.

This thesis contains studies of several solutions of non-metallic compounds in strong acids. The principal solvents used were concentrated sulphuric acid, oleum, and antimony pentafluoride. The blue solutions formed by iodine and some of its compounds in strong acids have been investigated by various methods. The results obtained are shown to be more consistent with the formation of a cation I2 + than the cation I+. No evidence has been found for a similar bromine cation, Br2+. Sulphur also forms blue solutions in strong acids. These have been studied by electron spin resonance and other techniques, and the blue species is believed to be of the form X2 SSX2+, where X is derived from the solvent. Similar solutions of selenium and tellurium give no evidence for similar species. Electron spin resonance studies of solutions of tetrasulphur tetranitride in sulphuric acid and antimony pentafluoride have been interpreted in terms of a species S2N2+, with a square planar structure. The previous suggestion of a species SN2+ has been rejected. The anthracene cation, C14H10+, has been prepared in solution in liquid sulphur dioxide by the action of antimony pentafluoride on anthracene, and has been characterised by electron spin resonance. Similar experiments with naphthalene and benzene failed to give conclusive evidence of the cations C10H8+ and C6H6+. Electron spin resonance studies of solutions of the complex XeF2.2SbF5 give evidence for the presence of a radical with magnetic interactions with three fluorine nuclei. Further characterisation of the radical was not possible.