Spectroscopic studies of coal and an ESR study of mono and dicarbonyl radical cations
Part I - ESR spectra of pure coals, oils and tars are presented; their g values and linewidths are calculated. Almost all the spectra are single, broad resonances; but one coal, Hucknall Coal, exhibits a two line spectrum, a narrow line superimposed on a broad line. On admission of oxygen the narrow line is reversibly lost. On the addition of various solvents to the samples, in most cases, an irreversible loss in ESR signal intensity was observed. There seems to be no direct correlation between which solvent is added to which coal and the effect on the ESR signal intensity. Infra-red spectra of pure coals are studied, both as pressed discs and thin films, and a method for the preparation of these discs and films is given. Solvent addition experiments were undertaken and the results show the breaking of weak coal/water hydrogen bonds and the formation of stronger coal/solvent hydrogen bonds. Part II - ESR spectra of the radical cations of several mono and dicarbonyl compounds are presented and interpretation of these spectra are given. For most compounds the parent radical cation is seen, with the spin on oxygen. The cyclic dicarbonyls show the σ-bonded structure for the cation with coupling to the protons δ to the spin. Some non-aldehydic dicarbonyls show a rearranged structure with the spin on carbon. The aldehydic dicarbonyls all show, in addition to the parent radical cation, lines due to an acetal type species, as yet unidentified. Some compounds containing nitrogen or sulphur in addition to oxygen have the spin localised onto these alternative heteroatoms.